XV Yamaha Electrical Trouble shooting...

wiring diagrammes, how to's etc
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XV Yamaha Electrical Trouble shooting...

Post by Cromag »

3 x the vomit, (84 XV1000) ive been doing electrics today, ive got everything working (havent yet hooked up blinkers and tail light, but have them marked as ive figured it out) but dont have spark.

Ive pruned the main loom by starting from scratch and leaving everything i can get away with off...i think its something to do with cut out switch (stock on right handle bar switch- why because when i use it, nothing changes and the wires to the coil/all of em are hot/power) any ideas as to what i should be looking at?
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Post by Chucky »

If this doesn't help nothing will, found for your pleasure at drpiston.com



When you suspect ignition problems, first be sure that your battery is hot, etc. (mentioned above), An inexpensive digital multimeter is a must to work on ignition systems, so if you don't have one, bite the bullet and get one. They also make an inexpensive spark tester which you can attach into the plug cap and which may help tell you if you have spark, and how strong that spark is. I have linked a copy of the test procedure (as shown for '81-'83 bikes in the factory service manual) to this article.


The wire windings in coils touch each other. However, they have an insulating skin on them and so one winding is insulated from the next.

I know of only two things that can happen to windings. The wires can break causing an open circuit or "open". Or the insulation between windings can break down, allowing the actual conductors to touch--which allows current to jump across windings. This can be called a "short". In testing a coil, an "open" will show up as lack of "continuity" or an infinite resistance condition--no current gets through. A "short' will show up as an out-of spec resistance number (probably lower) as current jumps across windings. The only other point to keep in mind is that metal (and wire is metal) expands a little when hot. Occasionally windings will start touching and "short" when they heat up, whereas they will test O.K. when cold.


In Viragos, pickups are generally very reliable. But they do live in a harsh environment which includes very hot oil while the engine is running, and great temperature swings. The wires connecting them to the TCI also have to run in this environment during their travel inside and through the side cover. So occasionally pickups, or their connecting wires, may have a problem.

A resistance test is given in the manuals. You can perform this resistance test by finding the connectors for these wires (under the seat). There should be some resistance. If there isn't, it may mean that the wires have become frayed/damaged inside the side over, and are shorting out on the engine casing. Beyond this testing, the only option that I know would be to install "a known good one" and see if the problem goes away. If you remove the sidecover for any reason, always be sure to check the wires running from the pickup for fraying or damage that could cause shorting.

One point of slight interest is that these pickups trigger a spark once every time the flywheel rotates, whereas the engine (being 4 cycle) only needs a spark every other time. What happens to this extra spark? Well, it occurs when the piston is reaching TDC (top dead center) on the exhaust/intake stroke. The exhaust gasses have just been pushed out of the cylinder and the new fuel/air mix is just starting to enter. So there is really nothing around to explode, and the spark just happens, but produces no result and does no harm.

The only source for new pickups that I know of is Yamaha. Note also that the design of the pickups changed at some point, wth two wires coming from them (one each and an engine ground) as opposed to two wires from each for a total of four wires. So pickups from different models are not necessarily interchangable. Check part numbers before you go on E-bay and buy a used set.


What can happen to TCI's? Sometimes individual electronic components inside them can fail. Also, heat and vibration can cause the solder runs on the printed circuit board to crack and develop breaks. Sometimes the basic sparking circuit is good, but the advance circuit may have problems, or vice versa. You can check whether the timing advance circuit is acting properly by removing the round cover on the left side cover and accessing the timing window. Then, using a common timing light, you can watch the timing advance (the timing mark will move) as you rev the engine. There is no timing advance adjustment available on the virago. The pickups are not movable..

TCI Symptoms can be pretty strange. I had 920 which would start easily but would begin to run badly when it was half warmed up. Then things would straighten out and the bike would run just fine (until one day it didn't, and I went ahead and replaced the TCI.)

Yamaha gives no electrical/electronic tests for these boxes, so trying a known good one (not always easy to find) or "replacement" are the only options they offer for us laymen. Note here, that the design of these boxes has changed a number of times over the years, both internally, and in respect to the style of connectors, so that they are not necessarily interchangeable. On later models (1984 up) the connector may look the same but still some boxes may not work in other models. Also XV 1000's and 1100's have a "pressure sensor" input to the TCI that 700's, 750's, and 920's don't have. This "pressure sensor" relates to spark advance but Yamaha isn't specific on exactly how. I think it retards the spark on deceleration. So when looking for a "known good one", be aware of these things. Obviously, if you can find one from a bike just like yours, that's best.

If you decide to replace a TCI, you can go to Yamaha and pay big time, but there is now at least one other source (K&L Supply)) and you maybe able to find others. K&L Supply charges around $300, I think. It does not sell direct, so see your dealer.

However, there is another option. TCI's can be checked out and repaired by qualified electronic techs. I have a local (S.F. Bay Area) shop that will do this for around $100, and you can probably find others on the net or locally. In the case of the earlier boxes, some component parts are no longer listed in current catalogues, but my guy has been able to find crossovers/substitutes among currently available components. I give his contact info at the end of this article.

I have never seen a set of circuit diagrams for these boxes and wouldn't know where to find one. But I have heard from electronics guys who went into their TCI's, and figured out what was going on in there without too much trouble. They soldered up breaks and replaced components. So those with electronics training may be able to take a crack at it.

A common question I get about bikes built in '84 on up is "Where the bleep is the TCI?" Well, it sits on the back fender. The easiest way to get to it is to remove the seat, drop the back fender (four bolts, I think) and let it rest on the rear tire. Then you see it and can get to it. A relatively easy procedure.

The one "quick fix" I have seen work, is simply to unplug and replug the TCI connector(s). Sometimes these connectors can develop a little corrosion or resistance which can be fixed by this simple operation. A little WD40 on them might not hurt.

An occasional ignition problem which defies intuition, involves the tachometer on the Virago. The tachometer takes its signal from the TCI wire to the #1 coil on early models or from the same circuit inside the TCI on later ones. Once in a while a tach will develop a short, and this plays hell with the signal. As a result the back cylinder starts to misfire. Doesn't happen often, but keep it in mind if this is your symptom and everything else checks out. The quick test is to disconnect the tach and see if that corrects the problem.

One final point while we're here. People tend to use the term TCI and CDI interchangeably. But they are not at all the same thing. TCI's replace the old "points" with a better solution involving transistors and no moving parts. The CDI (standing for Capacitive Discharge Ignition) builds up a big whack of voltage in a capacitor and sends it to the primary of the coil. The magnetic field build-up is sufficiently quick and powerful to cause the secondary to achieve high enough voltage to make the spark. So the TCI is a "break" technology, and the CDI is a "make" technology.


What can go wrong with coils? The same things that we discussed in regard to pickups. Heat and vibration can cause opens, or shorts between the windings due to insulation breakdown. The manuals give resistance tests for both primary and secondary windings, and if a bad coil is suspected, that would be the first thing to do. As with any coil, you may occasionally get a good resistance test when cold, but still have problems when things warm up.

If your problem is clearly with only one cylinder, you can switch coils and see if it jumps to the other one. If it does, the coil is probably bad. If it doesn't, both are probably good.

Note that the manuals can confuse you in regard to the amount of resistance in the secondary winding. To be clear about it, the correct resistance for the coil secondary winding is around 8.5K ohms at room temperature for '81-'83 bikes, and around 13.2k ohms for '84 and up bikes. But if you take this measurement through the stock spark plug cap, as you are directed to do in some manuals, you are going to pick up an additional 5K ohms from the stock plug cap for a total resistance of around 13K/18k ohms. So be aware of this little glitch.

A fairly common practice when trouble shooting a bike is to run the engine on one cylinder by pulling off the spark plug cap to the other cylinder plug. This does no harm to the engine provided you don't overdo it. But it is very important to GROUND THE PLUG WIRE CAP ON THE UNUSED CYLINDER. (An easy way to do this is to stick in a spare plug and lay it on the cylinder head). If you don't ground the coil secondary, it will build up all that fat voltage with no place to send it. It will overheat, and potentially hurt the coil. Remember that "nice girl" in the back seat of your car who wouldn't "go all the way"? And the ache you felt on the way home? Well your secondary will ache just as bad, and really needs to "go all the way" every time. But I digress.


In my experience Virago spark plug wires don't cause problems, and you mainly inspect the insulation to look for cracks or other signs of breakdown. If you can feel a kick from one while the engine is running that's a sign that there is a leak somewhere, caused by a crack, or maybe dirt on the outside of the wire. As noted earlier, the wire itself should be good for a very long time.

Spark plug wires can be replaced. What you would use for a replacement? I'm not so sure. My local Yamaha dealer sends people to the auto store and tells them to buy "hard wire" cables. That means with metal, rather than carbon conductors.

Some Virago coils come with their "high tension" wires molded into them, and it looks like you'd play hell trying to get them out to replace them. However, there are splicing kits available which would allow you to cut the wire close to the coil and replace the rest of it with new. These kits maybe more available through auto supply stores than through dealers.

Spark plug wires screw into the spark plug caps, and also into most of the coils. (This is the old fashioned method, but it seems to work O.K. for us.) While there is a rubber dust seal around these joints, sometimes corrosion can start to develop in the tips of the wires. A quick and sometimes effective cure for spark problems is to cut 1/4 inch or so off the ends of the wires to access some fresh strands, and screw the plug cap/coil back in.


You can measure the resistance in your plug caps very easily with your multimeter set to ohms. Should be in the 5K range. Beyond that you can inspect for physical damage-cracks, etc.--and make sure that the cap grips the plug tightly. Plug caps can wear out eventually (all that voltage pounding through that resistor, I suppose) but are easily replaced, preferably with ones of similar resistance.


First you can check the numbers to make sure they are the right ones. Then you can to see that they are gapped correctly (.028-.031), and don't show excessive electrode wear. Then you can make sure they are clean both inside and out. And if you want to, you can touch your ohm meter to both ends of the center electrode to assure continuity. I've seen one or two plugs that failed this test. Resistor plugs may have an air additional gap inside them and so would not check out this way.

Removing And Installing Plugs

When removing a plug, the best thing to do is partially back it out, and then blow out the well (or clean it some other way) to remove any crud that has accumulated down there. That way dirt doesn't drop into the cylinder when the plug comes out.

Plug bodies are steel and cylinder heads are aluminum. With two different metals corrosion can occur. When refitting plugs, make sure the plug threads are clean. I usually go down into the plug hole (if I can reach it) with a Q Tip soaked in carb fluid, and try to clean up the walls a little as well. If you want to do what the pros do, before screwing the plug back in, smear a SMALL dab of antiseize grease (available from your auto parts store) onto the threads which will lube them, cut down possible corrosion, and make removal easier, while not affecting the ground connection.

To tighten plugs you can use a torque wrench or tighten by feel. For a new plug, the washer will crush. Used plugs obviously have flattened washers. I'd say tighten a plug until it is good and snug, but be very careful not to over-tighten.

Cleaning Plugs

A dirty plug in otherwise good condition can be cleaned and reused. Since I sometimes do tuning work on my bikes which involves plug reading, my plugs are going in and out quite a bit. So one of the best acquisitions I have ever made is an inexpensive (about $35 as I recall) sand blaster type plug cleaner that runs off my air tank. It does a very good cleaning job and the only thing to be careful of is making sure that all the grit is out of the plug before you reuse it. I assure this by spraying carb cleaner and using direct air to make sure the plug is totally free of grit, inside, under the gasket, and on the threads.

The next best way is to go after the plug with carb cleaner, and little brushes, tooth picks, whatever it takes to get down around the insulator.

The basic problem with dirt in and on a plug is that it can form an alternative path for the spark voltage to travel to ground. The current takes the easy roadand avoids the plug gap.

For the same reason, a gas fouled plug won't fire. If a plug gets wet from a flooded cylinder--even if it is brand new, or otherwise pretty clean, it will likely need cleaning before it will fire again.

The same thing can occasionally happen on the outside of the plug. In wet weather or other conditions where moisture builds up on the outside of the insulator, the current can sometimes find another way. In moisture situations, WD40 sprayed on the plug wires, caps and plugs can sometimes help. "WD", after all, does stand for "water displacement."

Reading Color

Looking at plug tips is helpful in learning about what is going on inside the cylinder. If you are running rich, the center of your plug (electrode and insulator) will be somewhere between dark and black with carbon. If your plug is misfiring due to faulty ignition it will also be black and possibly wet. Many manuals have color pictures showing what the different conditions look like. Where it gets harder is knowing when you are dead on with your carburetion. Reading plugs used to be more reliable, but now, due to gasoline additives and leaned out bikes, plugs may not show small differences. In general, whitish to light gray to light tan should be good, with mid chocolate being on the rich side but O.K. Bone white may indicate a lean condition, but many plugs will look that way when there is really no sign of lean running or overheating. Note that the color around the edge of the plug body is usually dark and indicates conditions present mainly when using the choke and on start up.

Extra Plugs

I generally carry a set of extra plugs just for the heck of it. One situation where they might come in handy is if you have to go over a high altitude pass. Altitude will make your engine run rich, and the higher you go (especially if you have been running a bit rich at sea level), the more likely you are to foul plugs.


Hopefully this article has given you a better understanding of the basics of the Virago ignition system. As you can now see, when a cylinder quits firing and you have checked out your fuel system (running problems are more usually carb related, than ignition related) and figure it is ignition, there is no one-shot, easy, quick fix that will work every time. You have to start testing, checking and certifying components until you find the problem and/or the peccant part.

An inexpensive multimeter is a must for this work.

As usual, nothing helps like some good "peer review" so comments and corrections are encouraged and appreciated.


NGO="Known Good One"

Make sure battery is hot
Use a spark tester to determine if you problem is really spark
Check wiring connections
Make sure power from the sidestand switch is good
Where one cylinder is involved swaps (e.g. coils, plugs, plug caps, etc.) to test componts are sometimes possible

Run resistance tests
Inspect wires--they can get frayed where they come out of the side cover

Unplug and replug
Check advance function through timing window
Try an NGO (from same or similar model as yours)
Unplug tach if you suspect a short (#1 cylinder having problems)
Have the TCI checked and repaired by a qualified electronic tech

Run resistance tests
If only one cylinder involved, try swaping coils
Try an NGO

Check for leaks, cracks
Cut a bit off the ends to access fresh strands

Check resistance

Check gap
Clean after each try if plug gets wet (from misfiring) sooted up from rich running.


Note that the web is a good thing, and a Google search will often get you some good sources for all kinds of things. The following represents the few that I know about. There are probably others, so get out there and do some hunting on your own.


TCIs new: Ignitech. (easy to find on web) This is a Czech outfit that offers new TCI's at reasonable prices. Language is a bit of a problem, but an email to them should get results.

TCI Repair: Mastertechs (Jonathan Cabading) Petaluma, CA. Telephone 415 883 0368 (no e-mail)
CAUTION--While I think Jonathon can do this, I have had one negative input on this guy.

A letter from Dave Denowh
Dear Mac,
You have graciously referred to my service on your Virago Tech page for some time now. I thank you very much for that. I have reconditioned over 750 Virago TCI ignition modules over the years! That's a lot of Virago's saved from the scrap heap :) My current charge is $99 which includes return shipping.
My web page location and email have changed and I wonder if you would like the new info. I do not have a special URL, just a link to space on my .mac account.
My new email is tcirepair@comcast.net
Thanks much,
David Denowh
Rockford Illinois

TCI New: K&L Supply Co. Around $300, I think. Access through your dealer. Or Yamaha.

COILS: Yamaha. There maybe alternative sources--I have never had the need to replace a coil.

PLUG WIRES: Auto store (hard, that is, metal wires.)

PLUG CAPS: Yamaha dealers should have them

PLUGS: Yamaha dealers, or any place that carries NGK

SAND BLAST SPARK PLUG CLEANERS: Loads of them on the internet for around $21. J.C. Whitney has 'em

Updated 6/06
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Post by Cromag »

What an informative right up...lots of info i can use....when its running....nothing here really gave me a clue as to what i need to do to find that elusive spark.....if i have spark and its going pear shaped this info is bound to be helpful. Thanks (a really good article, i wondered what a TCI unit was).
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Post by cjmeg »

Cromag wrote:What an informative right up...lots of info i can use....when its running....nothing here really gave me a clue as to what i need to do to find that elusive spark.....if i have spark and its going pear shaped this info is bound to be helpful. Thanks (a really good article, i wondered what a TCI unit was).
TCI + Transistorised Coil Ignition (or something like that)
A lot of kill switches kill engine by grounding the ignitor through the switch.
Others complete the circuit to the coils.
A wiring diagram will show twhich one - usually transistorised ignitions use 12 V coils, often having kill sitches that complete circuit
Where CDI (capacitor discharge ignition) use high voltage coils, tending to have a swicth that shorts to earth.
Either way, you "should" be able to remove the kill switch and still get it running.
Hope that is of help, Glen
Time to start playing with the Vmax.
Oh and maybe I should finish the trike too!
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Joined: Tue Nov 15, 2005 10:58 am
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Post by Cromag »

Ill give it a go. Thanks.
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