TCI & CDI Electronic Ignition / Stators & Charging Systems

This guide was started for the "YAMAHA VISION" motorcycle group ( However, much of this info applies to any ignition / charging / electrical system. Specifically, how this stuff works, how to trace problems, and ultimately how the driveway mechanic might fix an electric, ignition -or- charging problem . If you have comments or corrections... PLEASE email. I will update this when I can. ©1999   Dave "Leather" Draper   . My Vision Info Site Here.

"Yamaha Vision" Motorcycle
Electronics / Ignition FAQ

Version 4.0

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Download This Entire Guide As PDF

Main Links

How Does Electronic Ignition Work?  

The basics & big picture view of typical ignition systems

Charging Systems and Stator problems  

Basics of motorcycle charging

Disassemble & Repair An Ignition Box

How you might fix a x550 Vision TCI

How TCI Works (jump on this same page) Jump on this page to Vision TCI discussion

Electricity Guide

Battery Guide

Top Vision Links

Yamaha Vision Riders Group

Vision Resources Page

Top Ignition Links
ElectroSport Makes ignition/charging parts (was known by Electrex)

Yamaha XZ550RJ/RK Ignition FAQ Table Of Contents

=== A P P E N D I X ====

1.0=> INTRO

The document you're reading here (and below) is primarily about the Vision Electronics with emphasis on solving ignition problems. If you want to read about how most all ignitions work then open the new page on ignition basics listed above. If you want to understand basic motorcycle charging systems or have problems specifically with the Vision open the new charging page listed above.

If you're already convinced your Vision TCI is bad and are motivated enough to try a fix it, open the new page above on fixing a TCI. We have not had anyone document in detail fixing a TCI but clearly know that it has been done. Would be great to hear from someone who has done it.

There are also 2 other pages dealing with basic electronic theory and batteries.

The ‘82/`83 VISION has a "Transistor Controlled Ignition" system ("TCI"). This type of ignition is used on many older non-automotive motors (look at a Virago...) and is closely related to modern Capacitive Discharge Ignition ("CDI") systems. While technology advances bring us to the computerized ignition systems of today, the principles of ignition have remained fairly the same.

The 2-cyclinder Vision motorcycle TCI system consists of :

- 2 sensor pickups under the crankshaft cover
- magnet on outside edge of flywheel (triggers sensor pickups)
- 2 spark coils (1 for each cyclinder)
- a solid state module box ("ignitor") that controls the spark

Solid state (electronic) ignitions were introduced in the early 70's (my '72 Outboard has one), became widely used in autos in the mid 80's and are now common on ALL motors. The Vision ignition has the typical problems associated with older (and poorly built) solid state ignition systems. The sensors or control module will fail completely ... -OR- ... (more frustratingly) the ignition becomes erratic and usually increasingly worse when hot.

Electronic Ignitions fail usually due to:

- electronic components (switching transistors) in the system breaking down with heat (older transistors were not as good as today)
- material defects (bad or broken solder joints)
- corrosion and bad connections to the module or inside the module
- normal life span ("MTF" mean time between failure rate) of older electronics (diodes, transistors, etc)

Lets face it, electronics don't last forever and I'll bet you don't have your first stereo anymore either (or do you ?!?!! you cheapskate).

A Vision TCI cost about $400 new and about $50 used. If you have ignition problems you know your ride is not worth too much more than that. Still… it's a great ride!! If you want to fix it affordably here's your best chance. Eliminate ignition problems in an organized progression and you will minimize the chance of buying a expensive parts you really didn't need. (..... example: "put the coil back, you really don't need a new coil" ......)



You want to narrow down ALL the possibilities before you replace a TCI, PICKUP, or COIL. If you can get (beg, borrow, steal ..) a good spare ignition then DO IT.   Bottom Line... You have 2 coils and 2 pickups. So you can eventually tell if one is BAD by using the other in its place. BUT there is no "SURE" test of the TCI. You can prove it's bad, but you can't prove it's good. Eliminate every other possibility and then you know it's a TCI module.

  • REMEMBER Some Comon Sense Stuff
    • Plugs really do foul bad enough not to work (check spark with plug removed)
    • Don't confuse ignition symptoms for carb problems (again, check for spark)
    • Bad connections (voltage dropout) and fuses can produce all the same symptoms of bad TCI/Pickups
    • Dude ..... Is Your Battery Good ????


Exactly "WHAT IS GOING ON" ?? Take your time and write it down. Try to pin down your symptoms:

-Is just ONE cylinder misfiring? Which one? It makes a difference!
-What is the Tach doing during the problem since the TCI drives the tach too
-What conditions make it happen/worse?..after getting hot / been running awhile / bumps / etc..

top2.3 [Quick Check List In Priority Order]

[   ]  a. Fuses [   ]  i. TCI Power On Test
[   ]  b. Connections [   ]  j. TCI module Power/Voltage Checks
[   ]  c. Voltage Dropouts [   ]  k. TCI disassembly + inspection
[   ]  d. Battery [   ]  l. Sensor Ohm Check / Swap Test
[   ]  e. Spark Plugs and Wires [   ]  m. Coils Ohm Check / Swap Test
[   ]  f. Side Stand Relay
[   ]  g. Engine Stop Switch
[   ]  h. Rev Limiter Wire

2.4 ["The Matrix"]


Possible Problem / Solution

 Front Cyl ONLY misfire / Inop
Sparkplug fouled or Plug Wire bad
Rev Limiter ->
     cut Yellow/Black wire at TCI 6-prong plug
Front Pickup -> check / swap
Front coil -> check / swap
TCI -> check / swap
Rear Cyl ONLY misfire / Inop
Tach Works fine
Sparkplug fouled or Plug Wire bad
Rear Coil -> check / swap
Grey wire Bad From TCI to coil
         {TCI is triggering tach correctly, sensor good}
Rear Cyl ONLY misfire/Inop
Tach Jumps around wildly or inop
Rear Pickup -> check / swap
TCI -> check / swap
 BOTH cyl die together, bike won't run
Tach dies also (goes zero)
 Side Stand Relay ->
     Cut Black/White wire at TCI 6-prong plug
TCI-> Check/Swap (Try Power On test).
 BOTH cyl die together
And starter won't work
  Run switch bad -> Try Separate 12v wire and test
Both cylinders misfire
Engine runs real erratic
May run fine high RPM but not low
      (or visa-versa)
May not start or spark at all
Worse when hot
Most likely TCI problem or bad connection to TCI

Check connections and voltages
TCI -> power on tests
TCI -> Inspection
 Ignition good till under load
Bad Battery
Connections - Voltage drop somewhere
 Ignition good some days not others
 Bad Connections
TCI -> Open Inspect for obvious flaws / moisture


top3.1 FUSE BOX

The fuse box under the seat should be replaced. Especially the 10amp ignition fuse! It provides +12v power to the ignition module / coils / safety relays. A poor connection here can result in ALL of the ignition symptoms!!


Replace each fuse with plastic "ATC BLADE" type fuses. Get the good ones with a rubber case and snap on tops. Look in a good marine store ("Boats US") or auto shop ("Pep Boys", etc...). Solder these inline into the wiring harness. Use shrink tubing / electrical tape / liquid rubber / or "Die-electric grease to insulate the connections from ground. The idea here is to prevent ANY corrosion from getting in these connections. IT CAN MAKE A REALLY BIG DIFFERENCE!


A GOOD technique is to use "Dielectic" grease to protect fuses and connectors. This is SPECIAL grease that WON'T conduct electricity. Get in good auto parts store. GET THE RIGHT STUFF or you'll have big problems on your hands. Dab the stuff all over connections AFTER THEY ARE CONNECTED (not before) you want to protect.


Most of the wire connections (especially in the plastic plugs) are "crimped on" connectors. These are especially prone to corrosion or getting "loose". A "BAD" connection is easier to find than a "POOR" connection. Here's why.

A "poor" connection will conduct +12 volts (shows good on your multimeter) but may cause enough "voltage drop" that there's really no power (amps) going to the thing its supposed to (TCI / COIL / PICKUPS). A poor ground or is EQUALLY BAD! -or- The connector will conduct 12volts ... but only enough to drive the mulitmeter... not the part you really to make sure is working!

If you're not sure what this means.... please read the section on Multimeter use / amp vs volts / testing good connections (Multi meter Use.)

My favorite technique when checking a circuit I'm not %100 sure of is to "plug" something into it to see if it works. A good 12v lamp (small headlight) is good for this. If the connection (or gound) will drive the light.... you know it can handle the load of whatever your concerned about.

Now you can check for these bad connections (read the the appendix section on multimeter use) BUT to my way of thinking just make all your connections "bulletproof" (replace if needed) in the ignition system and then you don't have to worry.

The telltail symptom of a bad connection is hot wires and/or melted plastic connectors.

NOTE : Look at the white plastic connector on left side of bike that connects the Rectifier to the Stator wires. This is a VERY common place to see the "melted connector" effect of a corroded connector. AND.... if this connector is bad the bike is NOT getting the electricity it needs. Most riders recommend you cut and permanently solder this connection to be absolutely sure.


To CLEAN the plug connectors pull them apart, clean them with a small file or knife. Some people like pencil erasers. Emery boards or 400 - 600 grade sandpaper are OK but remember to clean out the grit (... or you could make it worse). Apply WD-40 (or CRC) liberally to wash the gunk out. Reseat all the plugs. There are not that many. Specifically, remove right engine cover. Pull off the 2 plugs into the TCI “IGNITOR” module. Behind the cover the TCI is mounted is the "side stand relay". Reseat those plugs too.

top3.3 BATTERY

A subtle problem with motorcycles is it doesn't take much power to "crank" one. So, that's not always a good measure of the battery status. In fact, by the time your battery gets to sounding "low" on the starter its just about gone. AND if it "low" while running it could cause these symptoms: tach jump / tach dropout / random misfire both cylinders.




Pull the 6-prong plug off the TCI (you want no ignition for this). Connect the voltmeter to the battery and crank the engine. While cranking you should NOT see less than 9-10 volts. With the bike running at about idle (2000rpm) you should see about 13-14 volts.


This is more involved. But ... if you are motivated. As you suspect there is a good relationship between your battery and charging circuit ("STATORS"). The stators in the VISION are notorious. So this may be worth doing. You need a multi meter with a good Ammeter scale capable of 10amps or better. You are going to check the battery charging system while the bike is running.

1- Disconnect the RED cable from the +12 Positive terminal on the battery.

2- Hook the Ammeter between the battery and RED cable. Hook the RED test lead to the RED cable end and BLACK tester lead to the battery terminal. You are completing the circuit from the bike to the battery.


NEVER : DO NOT Run The Bike with the battery completely disconnected from the engine

3- Since you can't start the bike this way (that draws way more than 10 AMPS) you need to make another temporary connection alongside your multimeter (in parallel). Use a jumper cable

4. Start the bike. Then disconnect the jumper cable (the multimeter is still connected between the RED cable end and battery.... so the bike should keep running)

5. The ammeter is now showing the "draw" or "Charge" taking place to the battery.

6. Assuming your battery needs charging (almost always!) the needle should show a positive deflection at around ???? amps at idle and a little more as you rev up the bike.

7. Stop the motor. With it not running but IGNITION ON, look at the amp draw. Ignition and accessories should slightly peg the meter on the left side of case. If you want to see the exact draw swap the RED and BLACK TEST LEADS around. Amp draw without the motor running for stock VISION is about ???? with headlight in low beam.

*** NOTE: Read the Appendix section on Battery Care


Moisture inside the TCI module will produce ALL the ignition symptoms. This is addressed later BUT be aware the TCI is NOT a sealed unit like most ignition modules. WD-40 stands for "Water Displacement" on the 40th try (long story). The bottom line: spray a bunch on your TCI circuit board can't hurt.

top3.5 SPARK PLUGS         

Plugs rarely go bad BUT that doesn't mean you can rule it out. Because the VISION uses TCI instead of "CDI" (read section on difference) the plugs are more susceptible to fouling. You can foul a plug bad enough IT WILL NOT WORK! I fouled one this bad while experimenting for this guide. A good spark at the wire end (screw or nail inserted) doesn't show you what the plug is really doing.

Pull out the plugs, clean, and check for good spark with the plugs out and the case grounded. Look for a nice sharp blue colored spark that you can noticeably "hear". Try NOT to run your bike without the plug wires attached to something to spark to. Otherwise, you may encourage a spark out the side of the coil where insulation may be old and poor.



The side stand relay must be powered or the ignition unit is "killed". So, if the Side Stand relay or circuit is faulty it will cause the engine to cutout altogether (maybe intermittently). The key here is “ALTOGETHER”. Another words BOTH cylinders together. If the engine runs on ONE cylinder (ever) then THIS IS NOT YOUR PROBLEM. A faulty side-stand relay/circuit kills the WHOLE ignition. The tach WILL GO TO ZERO!

Now if the engine is running intermittently so rough you can't tell if its one -or- both cylinders then this is worth checking!

top4.2[HOW IT WORKS]

The VISION has a safety lock to prevent you from running the engine with the side stand down (and the bike NOT in neutral). In the VISION the ignition is “Killed” (tach goes to zero) when the BLACK/WHITE wire coming from the TCI module (6-prong plug) is connected to the frame = GROUND = -12volts. This is done by the “Side-Stand Relay”. Normally, when the side stand is up the relay is energized with +12 power and held “OPEN” to disconnect the TCI module B/W wire from ground. When the side stand is down, the relay loses power and closes, connecting the B/W wire to ground. So, if the relay is not "powered" (bad connections) or is shorting out …it can intermittently kill the ignition and tach.


Find the BLACK / WHITE striped wire coming out of the 6-prong plug in the side of the TCI ignitor module case. Either remove the wire-pin socket from the plug (harder to do) or just cut the wire and tape the ends. With the BLACK/WHITE striped the wire cut, the ignition can't be connected to ground and will work fine.

If this is the problem…. Fix/replace the relay or connections to the relay. If you leave the BLACK/WHITE wire disconnected… just remember your bike will run with the side stand down. Use your judgment, as this IS a safety device.

The side-stand relay is under the right engine cover, behind the plastic cover which the small square “TCI” ignition module is mounted to. That plastic cover also holds the water reservoir.


The run/stop switch on the handlebars provides +12 volts to the ignition, coils, starter cutout relay, and the side-stand relay. So it's unlikely this is the problem if you can get your bike to “crank” and start. BUT AGAIN, if your bike is cutting out (totally ,both cylinders, tach goes to zero) intermittently after you get it running… this could be the problem.


top6.1 [SYMPTOMS]

YES ITS TRUE!. The VISION has a "REV-LIMITER" circuit that kills the FRONT coil ignition if the TACH reads over 12,000rpm. The TACH reads the fire pulse from the TCI to the REAR coil (via the GREY wire from the TCI to the rear coil). That GREY wire splits somewhere under the gas tank. If the tach senses an over-rev it GROUNDS the Yellow/Black wire to the TCI. The TCI kills the front cyclinder coil pulse.

If the circuit malfunctions you'll most likely lose the FRONT CYLINDER ONLY (the tach falsely tells the TCI its overrevved). But, it could also kill the REAR too if the tach shorts out altogether and also shorts the Gray REAR coil trigger wire.

You will not affect ANY part of the ignition /charging system by disconnecting the Yellow/Black wire from the TCI.

Why would you want to keep the Rev Limiter? My best answer would be incase you drop the bike, its laying on its side running with the throttle somehow pinned opn.


*** CUT YELLOW/BLACK stripped WIRE in 6-prong plug at TCI *** (Tape the ends)


The Tach has 4 wires connected to it:

[BROWN] = +12 volt Power

[BLACK] = -12 volts Ground

[GRAY] =

Ignition pulse signal that the tach reads. It is a "tap" off the Gray wire from the TCI to the REAR cylinder coil. That splice is under the gas tank.

** That's why if you lose the rear cylinder ignition you lose the TACH. **

The GRAY wire signal from the TCI is a "square wave" trigger to the Coils primary winding. It is normally "near" ground and the trigger is +12v to fire the coil and pulse the tach. To be exact: in the Tach I dismantled the GRAY wire became ORANGE after the 3-prong connector block outside the instrument cluster (contrary to every wiring diagram I have).

[YELLOW/BLACK stripped wire] =

This is the Rev-Limit connection. This is a single wire between the Tach and TCI. When the "Rev-Limiter" switches ON IN THE TACH it grounds the YELLOW/BLACK wire. You can try this yourself. At the TCI disconnect the YELLOW/BLACK wire in the 6-prong plug in the side of the TCI. Then while the bike is running, ground the pin where the YELLOW/BLACK wire would be connected. It causes the same thing:

The "Rev-Limiter" KILLS THE IGNITION to the FRONT CYLINDER coil at about 12,000rpm.

If you're curious how I know this... I connected an "oscillator" to the Tach, powered it up and ran the tach up to... well, pegged. It thinks it's connected to the engine. At 12,000 exact (on my bike) it grounds the Y/B wire.


Inside the Tach are 2 small separate circuit boards. One is the Tach. And the other is obviously this "Rev-Limit" switch. I say "switch", but this is a "solid-state" circuit board switch (NOT a mechanical one). An IC chip on this board is obviously counting RPM.


".....plugging in a spare TCI is worth a thousand words....." - Author Known

top7.1 [SYMPTOMS]

There's are a million of them... but these appear most common:

- While riding one cylinder will stop firing intermittently at higher rpm. The bike still runs on one cylinder but with a lot less power and will be very hard to start if you stall it. The tach MAY go to zero when this happens. Typically this lasts about 2 - 15 seconds and then may cut back in and run normally.

- Both cylinders will alternately stop firing. Sometimes it will not run at all at low rpm. Tach is also at zero or may jump around wildly. Bike backfires badly, etc… Gets worse when its hot.

top7.2 [WHAT IS “TCI”]

Ignition systems have evolved over the years and been called many things: Solid State, Ignitors, Breakerless ,Pointless, Distributorless, etc... In outboards they're called "Powerpacks" or "Pulse packs". They go bad about every 5-10 years and also cost a boatload (excuse the pun). Yamaha calls this a "TCI" (Transistor Controlled Ignition) or "Ignitor" pack. In autos we call them "CDI" (Capacitive Discharge Ignition), ECU (Electronic ControlUnit), or DIS (Distributorless Ignition System). I will say TCI and CDI for simplicity but .....

top7.21 ["TCI" IS NOT "CDI"]

I Repeat ..."TCI" is Not "CDI"

The differences are subtle BUT you need to understand them or BAD things can happen

To be exact TCI uses transistor switches to disconnect the coils. This causes a charged coil to collapse and "fire" the spark. This is known as "Kettering" or "Induction" effect. So, in the VISION the coils are powered up all the time except while "collapsing" into spark. The VISION coils are constantly powered up at 12+ volts but the "induction" energy stored in the coils secondary core is about 20,000volts

TCI is an "INDUCTION" ignition system

CDI systems use a different technique. While the pickup and triggering is the same, the output from a CDI ignition module is a short high voltage pulse to the coil. In a CDI system the coil doesn't store the spark but instead AMPLIFIES the pulse from the CDI unit to a much higher level. The pulse is from the CDI module is normally about 250-500volts. The CDI coil acts like a transformer and steps the voltage even higher. A CDI coil typically steps up the voltage 100:1. Do the math and you see a modern CDI coil is outputing 25,000-50,000volts (Oh-Baby).The spark coils here are wired directly to ground and are waiting for the high voltage pulse from the CDI module.

"CDI CAN KILL" :That's why there are warning stickers all over your auto engine bay. The CDI module itself can give you a WICKED shock (not just the coil) and ...the coil output can KILL YOU.



top7.22 [CDI vs. TCI]

The higher output voltage of a CDI module produces a much higher cooresponding coil output voltage . So, CDI produces a much hotter cleaner spark. It is the ignition of choice among race teams and now widely used for everything. The "CD" in CDI means capacitive discharge. This refers to the high voltage output of the CDI module which comes from a "mini" coil circuit of its own. The downside to CDI is the short high voltage spark pulse duration. This is better at high RPM but makes starting difficult. You will notice many CDI ignition systems that use a starting "ballast resistor" type circuit. This circuit ups the spark output in the CDI ignition for starting only. TCI produces a longer spark duration (which some might argue is more reliable).

top7.23 [How CDI / TCI  works]

 Click On Photo For BIGGER

 Click On Photo For BIGGER

Pickup Magnet on Flywheel Outside

(2) Ignition Pickups (on right of stator)

A CDI module picks up a signal sent from a sensor usually otside the flywheel. The sensor can be optical (infared) but most often is electro-magnetic. In smaller or older engines (like motorcycles) the system is usually a magnetic rotor and coil pickup. The other "Hall effect systems" are usually used in auto or newer motors. Hall effect pickups are different and need to be powered, so there is usually 3 wires to those pickups. In the common motorcycle pickup a magnet on the flywheel passes by a small coil pickup. This produces a small electric pulse in the coil just like it does in your larger magnet-stator charging circuit. This small pulse is amplified inside the ignition module and used to switch a transistor which in turn controls the coil.

The flywheel usually has a combination of magnets and pickups. In the Vision, there is one magnet and 2 pickups (one for each cyclinder). Since there is no distributor directing which cyclinder gets the spark each cyclinder has its own coil. Or, 2 opposing (180degrees out) cyclinders can share the same coil and get twice as many sparks (1 in compression and one wasted in exhaust stroke (Refer to "wasted spark" section).

The gap distance between the magnet and sensor is very important as is the "phase" (when the magnet passes the sensor). The magnet is producing a "sine-wave" (low-high-low voltage) pulse for the CDI .The low to high pulse is the trigger. The peak voltage produced by most sensors is around 5volts.

In the VISION the 2 sensor pickups are under the left crankcase cover at the crankshaft flywheel end. The magnet is built into the outside surface of theVision flywheel.


The spark plug COIL is exactly that: 2 LONG lengths of thin wire wound side-by-side tightly around a cylinder spool (a “coil” of wire). The first PRIMARY WINDING length of wire is proportionally shorter than the SECONDARY WINDING. As example, the coil may have 100,000 wraps of wire around it but the second winding is 200 times longer ( wrapped 200:1 ….whatever). Since the wires are so thin and close, the second wire picks up the same electrical voltage (charge) flowing through the first. If the wires were the same length, connecting +12volts to the primary wire (other end to -12 ground) would charge the second wire up to 12v also. But, in a spark coil the secondary wire charges up to a voltage proportionally higher than the first since the secondary wire is so much longer (literally more wire to “fill” with electricity). Remember, the PRIMARY and SECONDARY wires are NOT connected. But they are just so close to each other that they pick up proportional charges.

In layman’s terms: when one end of the primary wire is cutoff, the charge still left in the primary wire flows back to the battery. But the longer secondary wire (charged now to HIGH VOLTAGE) is NOT connected back to the battery and its high voltage charge has got to go somewhere! It gets back to "ground" (the battery) by "jumping" the short gap in the spark plug (or YOU if you happen to be holding the plug wire).

In the VISION the spark plug coil has a constant +12 volts flowing into the “PRIMARY WINDING”. This causes the longer “SECONDARY WINDING” wire in the coil to charge up to a high voltage. When the +12 volts of the PRIMARY WINDING is briefly interrupted by the TCI, the coil electrically “Collapses” and causes the high voltage SECONDARY winding to discharge (the Spark). The input to the coil is +12 volts, but the high voltage output spark is over 10,000 volts.

 Again, the difference between "Induction" (TCI) and CDI systems is this:

TCI collapses an already charged coil by disconnecting it (TCI switches off briefly). These systems generally use a higher resistance type coil and are known as an "induction" or "Kettering" ignition systems.

CDI sends a brief high (200+) voltage pulse to an uncharged coil which act like a transformer and multiplies it even higher. The step up is normally around 100:1.  These systems tend to use low resistance or "racing" oils.

CDI modules normally use low resistance type coils. Remember that CDI is "shooting" a voltage pulse through the coil. TCI (or induction ignitions) use (and expect) higher resistance "induction" type coils. Remember current is flowing through the TCI to the induction coils continuously and the coil is fired when the TCI shuts it off. The importance of this is:

Do Not Use a "racing" -or- low resistance type coil in an "induction" ignition (or TCI) system.
The low resistance coil will flow more current thru the TCI and produce the legendary "Hot Toaster" effect. Though it will work for awhile, you will eventually burn the TCI module out.

In CDI this whole process of charge/discharge is near instantaneous. An 8-cylinder car running 5,000rpm is firing the single coil about 333 times a second. The output voltage of the coil depends on the input voltage and how much longer the secondary winding is. Some modern car ignition coils output well over 40,000 volts. This can KILL! The VISION TCI coil is probably (guessing here) about 20,000volts and if you get sparked will just shock the heck out of you.

top7.35 ["DWELL" -or- "DWELL ANGLE"]

Dwell time used to refer mostly to the mechanical time the distributor points are closed in old ignition systems. This affected the charge time of the coil and spark length. Dwell was important then because at higher RPM the dwell time was not enough to fully charge the induction coil. That meant less voltage spark at higher RPM (...BAD). There was also the problem of how fast a point could open and close without "floating" (a problem you have with valves also). There was a real balance between dwell time at high RPM, how much voltage you needed for high RPM spark, how much voltage you could actually push thru a point without burning it up, and then what would happen at low rpm (long dwell times) when all that voltage was just heating up the coils.

In newer CDI systems this term is near meaningless for several reasons. Solid state devices (like transistors)control the discharge pulses electronically with near instantaneous timings. So the dwell times can be finely controlled to achieve the best coil / spark outputs for a given RPM. Transistors can handle a LARGE amounts of voltage/current (compared to points). And, newer generation coils are extremely (microseconds) fast so charge / discharge times are not a huge factor (unless racing). Newer racing ignitions (like MSD) are NOT producing bigger sparks with long durations but in fact getting more effecient burn by producing very controlled multiple short duration sparks to the plug.

top7.4 [HOW the TCI Fires The COIL Exactly]

The flywheel pickup signal is fed to the TCI module. Inside is a “TIMING” chip which controls the length of the spark and also its timing relative to the RPM. As RPM increase the timing is advanced. In the VISION this is 10 degrees (“top dead center”) at 1,300rpm to 38 degrees TDC at 4,000rpm. Remember, in old engines the ignition timing was "advanced" with RPM by using a vacuum driven diaphragm or a centrifugal weight on the rotor. With CDI it is electronically advanced in the ignition "timing" chip based on some mathematical graph the manufacture has developed to maximize the engine horsepower in that RPM range (that was too a long sentence). If you have the VISION service manual you can see the timing graph on page 8-14.

The TCI module uses a "switching" transistor to "fire" the coil. This is how:

- The coil gets a +12 volt input direct FROM the battery (via ignition sw). It is grounded (the circuit completed) BY the TCI. The TCI transistor switches "OFF" the coil ground to collapse the coil and cause the secondary coil winding to spark. If you test the Gray (or Orange) wire FROM (that's right... from!) the coil you'll see +12 volts. If you look at the TCI pin you'll see near ground until the fire signal. Then the TCI actually pulses a +12 volts at the pin. This is a "forceful" way of "cutting"off the PRIMARY wire ground and forcing the SECONDARY winding spark.

The VISION has 2 coils (one for each cylinder). So, the TCI module has 1 timing chip and 2 transistors. One for each coil.

The VISION's 2 coils are mounted REALLY INCONVIENETLY under the gas tank inside the frame. To get to them you need to remove the gas tank. But coils VERY RARELY go bad! And when they do they usually stop working period (not intermittently). The odds are REALLY small they both stopped working intermittently.


There are no moving parts like relays/points/rotors to wear out or adjust. In theory, a CDI engine never needs an ignition tune-up again (you know, timing light, etc...) This is not always true. Remember, a car engine has 1 coil. They use a turning rotor under the distributor cap which determines which spark plug gets the spark. This does gets worn a bit since it involves a timing belt to drive the rotor and the rotor itself wears.

In the VISION there are NO moving parts because each cylinder has its own spark coil and there is no rotor.

In newer high tech engines you will see CDI ignitions with seperate coils mounted atop the spark plug for each cyclinder. This eliminates the distributor slop and radio interference problems associated with long plug wires.


> Electronic components HATE heat!!

That is why most CDI modules have lots of heat sink fins on them (Ever look how your Pentium chip is mounted?). DON'T leave your computer on all night!? But ...Yea-aah, don't turn it OFF and ON 5 times every hour either....?!? ...... because .......

> Integrated circuits also hate POWER SURGES!     .........and the THERMAL stress of going from cold to hot to cold.

The symptoms of ANY CDI type module going bad are very similar. They start to fail when the engine (and it) gets hot. They don't always fail altogether but gradually and intermittently as some or many IC components on the circuit board break down with heat. This is why a good electronic repair shop has cans of a "Freon" type spray (turn your "AIR DUST OFF" spray can upside down.... its the same thing). They will selectively chill each component till they can find the one that’s breaking down with heat. I'll bet many CDI modules that quit after start will work OK if you chill them down.


You Cannot Prove A TCI / CDI is Good. You can only prove that its BAD.

With the exception of newer automobiles and high end fuel injected marine motors .... manufacturers make NO "test bed"module you can plug a CDI into which will test if it's good. Worse, most retail parts shops will sell you electronic parts as is and you own them when you walk out the door (whether it turns out later you need them or not). A repair shop has the luxury of having some spares laying around. So they plug one in and see if it works. You can't aford this trial-and-error method because ....

Older CDI modules are pricey ("they" got you and "they" know it). Not just Yamaha or because you have a VISION. Don't take it personally. Most CDI modules cost around $300-400. The Yamaha "TCI" ignitor module costs $500 retail as of 2001 (at least you can get one). To soften the blow($) and REALLY to be safer outboard makers are now using separate CDI modules and coils for each cylinder. So when one goes bad it doesn't kill the whole engine and each CDI only costs about $80. And many bikes now use several of them for the same reason. If you do the math, you realize it may not be worth repairing. My wife always seems to be able to do THIS math !??. THANK GOD FOR EBAY !?


Most CDI units are encased in Epoxy resin or Epoxy-Rubber resin so you can't take them apart (Epoxy-Rubber resin will dissolves in acetone if you really want to see one apart) . They do this so moisture won't get in. The downside is heat buildup. WHAT YOU'D MOST LIKELY SEE is some resistors, capacitors, a couple transistors (you know, the ones that fire your spark plug coils). You'll also see the "timing chip". ANYWAY.... there's probably $10 in electronic parts and a $20 Ignition chip in a CDI module (I'm feeling generous). That a 1,200% markup!!. I'm in the wrong business.

What goes bad in these things?

Typically it is the "Timing" (Ignition) chip or the Transistors. The transistors really take a beating. That’s what generates heat in the CDI since they're essentially a switch going on and off at 10,000rpm ???. Put your hand on the side of your big wattage stereo amplifier: HOT, same thing! That’s where the heat sinks for the transistors are. And, the Ignition “Timing” chip is like any other IC chip. It's prone to breakdown with heat.


After reading all this, you'll be angry now when I tell you there's NO definitive test to check the TCI!

You can prove the TCI is bad, but not that it is good.

I recommend this order:

#1. The TCI "power-on test" (section 12) will show you right away if the TCI system is NOT working.
Go There Now -> TCI Power-On Tests

#2. Check the Sensors (section 8). This is most likely if you have one cylinder missing (not both).
Next Section

#3. Check TCI voltages (section 9).
Go There Now -> TCI Connector Checks

#4. Disassemble TCI for inspection (section 10).
Go There Now -> TCI Inspection

#5. Rebuild the TCI module.
Go There Now -> TCI Rebuild


 Click for big photo

  Click for big photo

Pickup Magnet on Flywheel Outside

(2) Ignition Pickups (on right of stator)

top8.1 [TACH symptoms]

Remember the TACH is DRIVEN BY the TCI via the REAR pickup sensor. If TACH is good, rear sensor is good.


If only ONE cylinder is misfiring then suspect all these: the PICKUP / COIL / TCI. Check all 3! It would seem unlikely for BOTH (one for each cylinder) pickups to go bad together at the same time. That would result in both cylinders misfiring. BUT - pickup sensor "crosstalk" -or- shorting is possible. That WOULD give those symptoms.


The VISION has 2 sensor pickups mounted on a single plate assembly. Each sensor pickup is a small "coil". You can check for "continuity" (no break in the internal coil wire) and also the correct resistance you'd expect of a coil that is not shorted out (or corroded).

Unplug the 4-prong plug from the TCI. At the plug the wires ends are :

BLACK = GROUND (connected internally in TCI to the Black ground wire in 6-prong plug).
This is the ground side of sensors. Both sensor grounds are tied together (one wire).

WHITE = Rear cyl Pickup.
RED = Front Cyl Pickup.

Set Ohm Meter to Rx10 scale. Put Black lead clip on the BLACK wire pin socket of the plug (use a thin wire or safety needle to get in there). Put the RED test lead on the RED wire socket. Then the WHITE wire socket. AGAIN, the RED+BLACK wires are Front cyl sensor, the WHITE+BLACK wires are the Rear cly sensor.

Sensor Pickup should read: 110 ohms (99-121 ohms is acceptable) in both cases.


The continuity/OHM test ONLY checks the basic properties of the pickup coil. It doesn't really tell you FOR SURE if its working. I had an outboard with single pickup that tested perfect years ago. Spent lots of money to replace the CDI and single coil because the engine would die after getting hot. But ultimately, it was a new pickup that solved the problem It had ALL THE SAME SYMPTOMS OF A BAD CDI module?!



Disconnect 4-Prong plug from TCI and check the male (protruding pins) on the module case. Connect the black test lead to the frame (ground), Ignition ON, and look for:

Black wire pin = Ground.
{Connected inside TCI to BLACK
ground wire from 6-prong plug}
Red wire pin = +1/2v (0.5v)
White wire pin = +1/2v (0.5v)

Put RED test lead on black wire and look for 0.5 volts when :

RED wire plugged onto pin (White wire disconnected).
WHITE wire plugged onto pin (RED wire disconnected).

If you have good power at the TCI pin but not after going through the pickup something weird is going on. Suspect a short in pickup or wiring (possibly where it goes into crankcase, etc...). You would have seen a break in the wire with the ohm test.

top8.5 [PICKUP CROSSTALK / SHORT symptoms]

Since the pickups share a common ground "crosstalk" or a short between the two sensors is a real possibility. "Crosstalk" would result in one sensor triggering the wrong coil. A short between the sensors could cause unpredictable symptoms


This is unknown. Without the schematic we're not sure how this works. Sorry dudes.


You are looking to make sure there is no stray ground in the wiring.

Put BLACK test lead on ground. Pull RED/WHITE/BLACK wires off (whole 4-prong plug) from TCI. Put RED test lead each wire end. You should not see GROUND. If you do suspect a short in the wiring somewhere to the frame or engine.

PROBLEM IS this may be happening with the vibration of the engine. This would be very hard to see. Because of the shared ground you can't run the bike even on one cylinder and check this.


top8.6 [SWAPPING PICKUPS {suspect one is bad}]

You have 2 pickups. You can use the good one to test your "Bad One" theory. Simple:

*** NOTE: DON'T SCREW THIS UP !!!! *******

If you keep a spark wire connected and start the bike with the pickups swapped ..... the bike WILL misfire B A D L Y

- Pull BOTH!! spark plugs off.
Insert screw into inop plug wire & position near ground.

- Swap the pickup sensor wires in TCI 4-prong plug.
Plug White wire onto Red pin and visa versa (Red wire onto White pin).

- Crank engine. If the bad plug fires (and good one doesn't)
then suspect the pickup ( OR COIL) is bad.
Test/Swap coil now and you'll know for sure.

top8.7 [TEST FIRING a CDI or TCI]

Obviously, if you can test fire the ignition module..... it narrows your troubleshooting quickly. Anotherwords... how can you "trick" the ignitor into thinking the pickup sensor has "pulsed" and/or get it to fire a plug? If your super lucky...your workshop manual will detail how this can be done. My 1973 outboard CDI could be fired manually and it was part of the factory service guide. The problem is.... there's no universal solution that I know of yet.... Certainly, you're not going to risk frying a good ignition module by trial and error. AND... unfortunately, the workshop manuals for most ignitors don't include this.

I will pass on a backyard trick as told to me by "roadrunner" but I HAVE NEVER TRIED. But it sounds like it should work. He writes:

"Just a quick backyead test. you can use one of them soldering guns, you know the hi current pistal type. It will trick the magnetic pickups to send pulses. becouse the gun creates a dense magnetic feald around the tip. Carfule not to burn something doing this. The pickups will sense these magnetic fealds and send firing pulses at 60 hz to the module . It makes it a lot easer to troubleshoot without kicking the starter each time ."


Get Haynes or Factory manual for this one. I will say this though. You must take GREAT CARE!! putting the crankcase cover back on and also how you seal (and sealant type)the wire bundle from the sensors out of the engine crankcase. If this is not done correctly you'll end up with an oil leak out of the crankcase and have to do it all over again.


The pickup sensor can fail and take the CDI with it (or visa versa). In other words, they can kill each other. Especially if a transistor shorts 12 volts through the pickup coil (you'd probably see an "open" pickup coil). Or, the pickup coil shorts to ground at higher temp and fries the transistors.



Disconnect the 6-Prong plug from the TCI module, Key ON, and check at the plug:

RED/WHITE striped = +12volts = power for TCI

BLACK = -12 ground = ground for TCI and pickups

ORANGE = +12v = power from Front cylinder coil primary winding

GRAY = +12v = power from Rear cylinder coil primary winding

BLACKWHITE = side stand relay wire. Should NOT be ground or +12 (side stand up! ).

YELLOW/BLACK = Rev limiter wire. Cut this + tape ends. Should NOT be grounded!!


Check that you don't have a bad wire or connection to/from TCI. You are looking for voltage "dropouts". You should not see more that 1/4 volts in these checks. More means you have a wire or connector that is literally diverting power or making a poor ground.

>> Set voltmeter to low scale 1-3 volts.

>> Put RED test lead on +12 battery post. Put black test lead on these TCI pins with wires connected :

RED/WHITE striped , ORANGE , GRAY wires


Plug both 4-prong and 6-prong plug into the TCI module. Use a safety pin to pierce into the correct wire and check same things above while the engine is running. Maybe there is a bad connection somewhere vibrating loose when the bike runs.


top10.1 [WHY LOOK INSIDE TCI ??]

If your convinced the TCI is the problem then this is your last hope. Open the TCI and look for an obvious mechanical problem like : moisture, bad solder joint, bad component.

top10.2 [GETTING INSIDE THE "Black Box"]

LUCKILY... you CAN look inside the VISION TCI module. BUT BE CAREFUL!! Take the cover off and your looking at the backside of the integrated circuit board.


It is held in by one small Philip screw, and MORE IMPORTANTLY, is soldered to the plug pins molded into the side of the case. To get the board out you have to desolder the pins or break them off when you take it out. You'd then have to solder them (or wires connecting them) back together. There is an easier way.

If you want to see the other side ..... cut a large "porthole" into the plastic "bottom" (other side of the case). Use a dremel tool small cutting wheel. This is risky because you can accidentally cut into IC components on the board. MAYBE BETTER, a sharp knife heated with a torch (so your melting through the plastic). Anyway.... GOOD LUCK (Could be a Darwin award recipient!).

Lay the case flat. Cut down (knife straight up + down) into the case about 1/2” in from the sides. Another words you're cutting a rectangular hole out of the bottom cover 1/2” smaller than the bottom cover size. One end of the module has the metal heat sinks which is why you need to cut about 1/2” in from the sides.

**** Cut no deeper than about 1/8" or you will cut into IC components ****


You will see the two "TO 220" style transistors with small aluminum heat sinks. The heat sinks are molded into the plastic case side so they're not obvious. In the center you will see the Timing chip attached in a "daughterboard" configuration. Everything else is diodes (the small end banded stuff) and resistors (center banded).

Look for obvious signs of heat damage (discolored components with blistered or crinkled skin). If you're REALLY lucky it could be a bad solder joint. Look for solder points that aren't pretty, look "dull" (cold solder joint), or look disfigured by heat. Chance are slim but... you never know.

top10.4 [MOISTURE]

The TCI is not a "sealed" unit. If you see any moisture then THIS COULD BE IT! I had a TCI with this problem once. Moisture really screws up resistances on an IC board. The case has 2 drain holes, but no good way for moisture to evaporate "out" out of the case. This is why most CDIs are encased in Epoxy-Rubber. Spray the whole thing liberally with WD-40. (If you didn't know "Trivia Pursuit Fans" ... "WD" stands for "Water Displacement" and WD-40 was designed for the military, in part, to dry out wet electronics). Afterwards, blow dry out with spray air (duster).






Have you heard "wasted spark" talked about? It is the spark you get during the exhaust stroke. It is "wasted"... but who cares. Here's the story.

top11.1 [Distributorless - Common Coil Wasted spark]

An automobile has ONE coil and a distributor rotor that determines WHICH cyclinder is getting the spark. NOT ONLY THAT.... but the rotor is geared to spin slower than the flywheel so that the cylinder ONLY gets a spark when it is TDC ("top dead center") on the compression stroke.

Fast forward to a motorcycle which is ALSO a 4-stroke engine but NO distributor and the firing sensors are on the flywheel spinning 1:1. You see where this is going ??

The Flywheel Pickups fire the ignition spark EVERY revolution. You get a spark on both the Ignition stroke and the EXHAUST stroke.

EXAMPLE: The VISION has 2 coils, one for each cylinder. Makers of some 4 cylinder bikes also use 2 coils!? So, two cylinders share the same coil AND (more importantly) get the SAME spark. Again, this means each cylinder gets exactly twice as many sparks has it really needs. One during the compression stroke and one during the exhaust stroke. WHY DOESN'T THE VISION (or 2 cyclinder) bike share 1 coil? Because you can only share a coil for opposing cylinders that are 180 degrees out. The Vision "V" configuration requires seperate spark coils.

This "wasted" spark is meant to simplify the ignition system. Manufacturers could cut the TCI circuitry in half and save coils , weight, and (OH YEAH) ... and money!!

top11.2 [VISION (TCI Induced) WASTED SPARK]

There is another phenomenon of "wasted spark" in the VISION. It's unique to ignitions wired like the TCI. Normal CDI ignitions do not produce this phenomenon.

top11.21 ["WATCH THIS!?!"]

Pull the rear plug wire off, insert a screw and position near ground. Power up the bike (either with ignition key to ON -or- Run/Stop switch OFF -> then ON). You'll get a single spark out of the rear coil about 2 seconds after power on. You get the same single spark out the front coil but its harder to pull that plug wire off with the sport fairing.

top11.22 [WHAT'S GOING ON?]

At key on (or Run/Stop to on), you power up the TCI and coils. The TCI then shuts down since their is no engine rotation. This auto-shutdown is common in all electric ingnition modules. It prevents the ignition from just sitting there powered up if the engine isn't running (which is bad for the transistors).

Since a normal CDI sends a short high voltage pulse to the coil, when it auto-shutsdown... nothing happens. BUT, the TCI is normally grounding both coils. It fires them by momentarily disconnecting the ground. You see where this is going? When the TCI auto-shutsdown, it disconnects both coil grounds. And sure enough, BOTH coils fire one spark out each plug.

Now, this same thing happens if you crank the engine (BUT IT DOESN'T START) and then let go of the starter. Since the engine stops rotating, the TCI shuts off and.... you get a single spark. This explains why you get a DELAYED single misfire/backfire after cranking but get no start. Especially if the battery is low. You have enough juice to crank but not for a good spark. Then you let go and get a GOOD full spark 2 seconds after as the TCI shutsdown. With fuel vapor in the carbs... bang. AND, since you're getting 2 single sparks regardless of where the engine stops... you could get it in a cylinder "valved" open to the exhaust which has fuel vapors in the muffler.... KA-POW!!

Now this is not the same "plug firing" you get IMMEDIATELY after letting go of the starter. In this case, you have managed to catch the timing just right. The powerful ("non-loaded-starter-battery") spark just happens to take place at the correct moment as you let go of the starter.


You can test the basic properties of the TCI modules power-up/auto-shut (read #11 above!). This is same for both Front and Rear coils. Read Appendix on Checking for Spark if not familiar.


> Unplug Front/Rear plug wire , insert screw, and position near ground.
> Set Run/Stop switch to STOP. Then turn ignition key to ON.
> Every time you turn the Run/Stop switch from OFF to --> ON you should see
a single spark about 2 seconds after power-ON.

If you do not see this spark then:

> coil is bad (check/swap coils, etc...)
> pickup is bad (this will not happen with sensor disconnected from TCI which suggests to me that it will not work with a bad pickup either)
> TCI is bad

To see if the TCI is trying to fire the coil check this:


> Disconnect GRAY or rear coil wire from TCI 6-prong plug.
> Leave rest of 6-prong plug + 4-prong plug connected to TCI (normal)
> At the GRAY wire pin on TCI check:

> At Power-ON the pin should read "NEAR" ground (see appendix for "near ground" if unsure)
(use the ohm setting, NOT continuity. It ISN'T a true ground connection)
> At 2 seconds after power-ON pin should go +12 (use volt setting)

If TCI is correctly trying to fire the coil, then you have a bad coil or wiring connection at the coil.

**** NOTE : Test is same for front coil (ORANGE front coil wire).

#13=> COILS

top13.1 [SYMPTOMS]

It is rare for a coils to go bad. It would beREALLY unlikely for both coils to go bad at the same time. So think about your symptoms. Usually spark coils either work or they don't. They are rarely intermittent. BUT having said that, coils can produce poor or erratic spark because:

- bad internal wire break or insulation so that spark jumps out the side of the coil (very affected by moisture in the air)
- internal short
- corrosion and poor connections

NOTE: It is always a bad idea to run an engine with a plug wire disconnected. That is because the charged coil want to "unwind" and if there is some leaky insulation in the coil it will fire out the side to the frame. After some time of this you can burn a hole thru the coil insulation and make this phenomenon permanet.

Since the coils are mounted REALLY inconveniently under the tank.... its worth checking what you can before dismantling half the bike. If your tests point to a bad coil... don't forget it could simply be a bad plug wire.

top13.2 [SPARK TEST]

Insert a screw in plug wire cap. Position near engine (a good ground). You should see a nice BLUE spark jump across at least a 1/8 - 1/4 inch gap. If spark seems weak suspect these:

>> low voltage from battery direct to coil via ignition switch
>> poor ground or low voltage from TCI coil trigger wire
>> Bad TCI timing circuitry
>> Bad Plug Wire

In theory I can't see how a bad pickup would affect spark strength... but who knows.

top13.3 [Ohm Test]

**** NOTE: Make sure you don't touch the metal connections here or your body resistance and moisture will throw the resistance readings off.

Check the resistance you'd expect from a good spark coil. Set a multi-meter to Rx1 and "Zero out" the meter. Pull off the 6-prong plug on the TCI.

Put Black test lead on the frame (ground).

TO Check the PRIMARY WINDINGS of the coil, put the Red lead into these plug pin connections below, both should read 2.75 OHM:

GRAY wire pin = Rear Cylinder Coil
ORANGE wire pin = Front Cylinder Coil

To Check the SECONDARY WINDINGS of the coil, pull the spark plug wire off each spark plug. Put the Red lead on each spark wire end. Each should be about 7.9Ohm.


If you want to test the "BAD COIL" theory then swap the coil trigger wires. Check to see if you get a good spark out of the coil you think is bad using the TCI pulse wire you know is good. This is like the pickup swap.

**** Don't leave the spark wires connected or you will misfire the bike BADLY! ****

- On TCI 6-prong plug swap GRAY and ORANGE wires.

- Disconnect BOTH!! spark plug wires. Put a screw into plug wire end and position near ground.

- Crank engine and look for spark out of bad coil. If you get a good spark then suspect bad PICKUP or TCI. Swap the pickups to confirm the TCI is bad.



If coil seems to test bad, could it be bad a BAD PLUG WIRE? A plug wire that has an internal break will still work. It can spark internally across the break. This could make the spark plug (end) spark weaker or erratic. You would have seen this in the Secondary ohm check though.

Also, the plug wire itself can have worn insulation. Then the spark literally leaks out the side into the engine (diminishing the one coming out the proper end)

You need to pull plug wire off COIL and spark plug. Check wire for continuity with voltmeter. And, look at the general condition of it. If you have doubts, replace it. THEY are CHEAP!


top14.1 [Ignition Burnout]

Don't leave your ignition on for a long period with the motor NOT running. You wouldn't normally do this but maybe if you forgot, etc… This can in some cases trash a CDI module (and pickups). The ignition has a circuit that is supposed to shut down power to the transistors and coil if the engine is not rotating. I suspect this circuit fails and over time the powered up TCI fries. That is why older cars always had a separate key position for accessories only.

top14.2 [Coil Care]

Avoid running the bike with the spark wire disconnected from the plug. Its OK if you've set up a spark test looking for the spark jump to ground. But if the plug wire can't "spark" somewhere this could damage the coil. The high voltage winding "WANTS TO SPARK" somewhere (ANYWHERE). Especially in humid conditions or with an older coil, the coil can spark internally which can wear/burn/damage the insulation between the Primary and secondary windings.



>> PINS : Standing at rear end of bike
Looking at side of TCI case as mounted on bike

>> PLUG : Looking at plug from socket end (WIRES OUT FAR SIDE)


You want to see the spark from the plug wire. Here's common method:

Pull the plug wire and "cap" off the spark plug. Insert a small thin clean screw into the plug cap. A screw is good because you can lightly screw them in for a good connection. Screw end should protrude about inch out of plug wire-cap end.

Position the plug wire (with screw sticking out) somewhere near a good ground. The engine is good or some clean part of the frame. Spark will jump through painted surfaces but the cleaner the better.

You are looking for strong "Blueish" colored spark to jump about 1/8-1/4 from screw end to engine (ground). If spark is weak make sure you have good connection inside plug cap.

Remember that this does not show you if spark plug is really working !


topA3.1 "Zero Out Multimeter"

Use a digital multimeter if possible. Its usually more accurate for ohm tests and diode test, but are harder to read. If you use an analog needle meter, remember you need to calibrate the display before getting an accurate ohm test. Connect both leads with metal clips only. Don't get your hands on them or it will throw off the reading. Adjust the meter so with leads connected the needle shows zero "Full-Scale" (last bar on the scale). This IS NOT "pegged to side of case"!

topA3.2 (Volts vs AMPS)

Remember, the Voltage is the "strength" of electricity in the wire and AMPS is the Volume passing thru it. The typical analogy is a garden hose. The voltage is the pressure of water coming out your faucet (usually 55psi). The AMPS is the volume of water. Obviously, 55psi coming out of your garden hose is LESS powerfull than 55psi coming out of a firemans hose. So AMPS is really the true measure of what the electricity can do. AND, obviously, the size of the hose (and wire) limits the volume=amps you can get. Notice the wire driving your starter is thicker than the wire driving your tail lights. Its the same voltage but you need to conduct more volume (amps) to the starter motor.

ronically, the bigger wire has a smaller size. WHAT?!? Its probably explained somewhere on the net but bigger wire has a smaller "gauge". So, a bigger #10 gauge wire will conduct more amps than a #14 gauge wire (without melting).For once.... smaller is better here.


When you use a multimeter to test a point on a circuit for +12 volts..... all you've done is prove it has 12 volts at that point. You still really don't know if the wire (at that point) is capable of supporting any kind of "AMP" load. This is where a multimeter can REALLY mislead you into thinking you have a good circuit. Anyone who has tried to fix rusty lights on a boat trailer knows what I'm talking about here. Its got 12volts but the lights still don't work !!?? Yeah..... thats because the corroded connectors can only provide 12 volts at like .1 amp. Enough for the multimeter but not for the lights.

SO...... how do you really check this if you think you might have "power" issues?

One technique is to test wire something to that point that really requires a solid +12 volts. A normal (not halogen!) headlight is good for this since they draw about 5-10 amps. You get the drift here. Wire something that requires real power and use it to check for your +12 volts.

CAUTION: Just make sure the item you use doesn't drawn too much power or you will blow fuses and/or melt wires (BAAaaaddd)

topA3.3 TESTING circuit load (TESTING AMP

Now, you can indeed measure AMPs on the circuit with a multimeter. You need to break the connection you're measuring and then wire the multimeter inline to complete the connection. To be exact you need to "complete" the connection using the multimeter in AMMETER mode. Then the meter can show both voltage and load.CAUTION: You must do this right or risk frying the multimeter

Most multimeters cannot measure amps normally. You must reposition the RED wire to another "AMP" socket and also switch the multimeter into AMP mode. Most good multimeters can measure up to 10amps which is good for automotive work. The small cheap multimeters CANNOT measure amps.

topA3.4 Voltage Drop

This is hard to explain and hard to grasp. Here goes. A wire normally has little resistance and so doesn't "use up" any voltage from the circuit. If a wire does have resistance it DOES use up some voltage and this normally translates to heat. Your toaster is the perfect example of this. Or in a badly corroded connection (like in boats) voltage leaks back to ground externally (like through the frame).

If you feel heat/warmth in any wire or connector something is not right !!.

This is hard to feel though (on a hot bike, on a hot day).

Your concern here is that the wiring in a circuit has gained some resistance of it own and is using up volts that would normally go to the TCI or Coils or whatever.

You check the end of a circuit with a meter and see +12 volts at the end. The whole circuit "path" is using and conducting 12 volts. BUT, the question is: what is the voltage at any given point along the circuit path. If the wire going to the TCI uses 1 volt, then the TCI in the middle is using 11 volts. It adds up to 12, but the TCI is NOT getting what it needs! Not good!

To check for voltage drops you need to hook the meter up "backwards" from what you'd normally do. You are checking points along the wire that are not a full +12 volts. You do this by comparing it to a good +12 volts. SO... hook up the RED lead to +12 battery terminal. You know THAT is a GOOD +12 volts as a reference point, right?. Now, use the black lead to check points along the circuit path.

If a test point is a good +12 volts you won't see anything ? You can't conduct +12 volts into +12 volts. But lets say a point on the wire is 11 volts because a previous connector is corroded and soaking up 1 volt.? You now will conduct 1 volt from the battery into the wire (there is a 1 volt potential difference). You will see 1 volt on the meter.

Generally, you should see less than a 2% voltage drop in a good connection (=.02x12=1/4volt).

Again : You should not see voltage drops more than about 1/4 volt.

topA3.5 "Near Ground"

In solid state circuits (especially) you do not always have "pure" ground connections. The circuit is "near" ground. You cannot see "near ground" on the Volt scale or Continuity setting. It is NOT a connection that can support that kind of electrical load. Use the Ohm x1 setting instead. The Needle will show near full scale when the probes are touched (use the adjust knob if neccesary). Now check the circuit. The needle will again show full scale with a good "near ground" connection. This happens when a circuit has some small resistance in it (solid state transistor grounds are good examples). The circuit sees ground. You will too if you use the right scale!

- Set the meter to Ohm scale like Rx1
- Put the test leads together and zero the meter (full scale needle)

- Now, put one lead on good ground (frame, -12 battery post)
- Put other lead on test point. Look for needle swing.

#A4 => [Battery Theory and Care]

This page courtesy of Aaron Berg XJ Electrical site. Open this Page NOW.

#A5 => [Removing TCI Wires From The Plug]

To Be Added


This page courtesy of Aaron Berg XJ Electrical site. Open this Page NOW.

#A7 => [Rebuilding A Vision TCI Module]

Open this seperate Page : REBUILD VISION TCI

Related Links:

David Denowh Virago TCI site

Allied Semiconductors

NTE Semiconductors

Fairchild Semiconductors

MSD Ignition Systems

Another Ignition Supplier

Accell Ignition Systems

Misc Ignition Stuff:

#B1 => [Author]

Dave "Leather" Draper A Face To-a-Name

I've added this to dispel any suggestion or myth that I am an expert on Electronics / Motorcycles / TCI / Ignition systems/meaning-of-life, etc.... I am an attack pilot/airline pilot by trade and have a degree in Computer Science and Mathematics. Over the years I have worked on a variety of motors. My father is a radio engineer so I have just enough electrical knowledge to be dangerous and enough mechanical skill to do some real damage. Occasionally it all comes together and something actually gets fixed. Around the house I am known as Mister "Fix-It" but that's just because my kids are still young enough to still believe everything I say (my wife 'cause I'm the only one who knows how to program the VCR). There are much smarter folks out there and that's the beauty of the net. Knowledge is power and I'm just trying to help spread it around.


(absolutely no particular order.... although I'll start with my dad who did measure all the component values of a TCI for us)
Bill Draper, Yamaha Vision Riders Group (You crazy guys), "Skip" Johnson", Dale Harris, Ron Ghetti , Jeff Swan, QBS, "Lucky", Aaron Berg, David Denowh, Dick Stelter, Brian Fosh, John Newton, Uwe Werner, Ulrik Moe Noe, rgaard, Steven Ware, Les Rowe, Ric Wade, Jouko Kuisma, Glen Scadden, Dennis Myers, Jim Gardner, Anthony, Apex Racing, Kriss from poland, George McQueen, Roadrunner, Bob R, Jens Eckartsberg, Fransisco Romo, Garret Spears, George Young, Electrex, MSD Ignitions, .....
... and everyone else I forgot: THANKS!


  • Rev 1.0 11/01/1999 = Original Guide
  • Rev 1.1 07/01/2000 =
    • Changed color Black on White for easier printing.
    • Added Electrical & Battery pages from Aaron Berg's XJ site
  • Rev 2.0 05/01/2001 =
    • Added PDF files
    • Added Ignition Links Section
    • Added Ignition Discussion Page
    • Added TCI Repair Page
    • Added Stator Page
  • Rev 2.1 10/05/01
    • Minor corrections from E-Mail feedbacks
  • Rev 3.0
    • Added many photos / updated text to other pages
  • Rev 4.0
    • Text update, corrections as emailed to me, and added larger graphics/images since almost everyone is somewhat high speed now and I have more server space (The original was limited to 5 megs !?)

(Except Images and where otherwise noted)
© 1999 David "Leather" Draper
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