Virago Ignition Systems

Simplified Ignition System(View)                   Yamaha Test Procedure 81-83 Models(View)



Before discussing the Virago Ignition Systems it is important to understand how the power to run it gets there.
The power starts at the battery and then travels through the main fuse, the ignition switch, the ignition fuse in the fuse box, the engine stop switch, and on to the TCI, and coils.

As circuit diagrams in the manuals will show you, these circuits vary somewhat between the ’81-’83 models and the ’84-up on models. But in both cases the TCI also needs a separate power input which comes in from the battery, and goes out to ground through what I will call the “safety system”. Power must be running in this circuit for the TCI, and ignition system to work.

The purpose of the “safety system” (no doubt designed by lawyers–but they couldn’t call it the “legal system”) is to save us from

–Taking off/riding with our side stand down, and

–Starting our bike when it is in gear (unless the clutch is pulled).

There are three switches involved in this system (plus relays) and these are 1. the sidestand switch, 2. the neutral switch, and 3. the clutch switch.  These switches make the ground connection for this circuit.  For our purposes we mainly need to understand that when the bike is in gear with the side stand up (the normal state of things when you are riding the bike) the “safety system” current goes to ground (current flows) by way of the SIDESTAND SWITCH.  This switch is “on” when the side stand is up, and “off” when the sidestand is down.

Note that when starting and idling the bike, you get this needed power through a neutral switch ground since the bike is in neutral.  But the moment you shift into gear the neutral switch goes off and that ground goes away. The sidestand switch must now take over.  If the sidestand is down (switch off), there will be no ground at all and the TCI shuts down the engine.  If the sidestand is up (the ground connection is made) then the TCI is happy and you drive off.

But occasionally the side stand switch sticks part way, or otherwise makes less than full and proper contact. The power input to the TCI may then be intermittent, or low in voltage due to excessive resistance in the switch.  In such cases your engine will run badly with various symptoms coming and going.  It is hard to riders to figure out what is going wrong because you wouldn’t suspect the sidestand switch unless you knew about it.  The classic symptom: Bike starts and revs fine in neutral, runs badly in gear.  If the sidestand switch  is plain bad, your engine will cut out when you shift into gear, whether your side stand is up or down.

If you suspect this the sidestand switch you can easily find where wires from it connect and then check continuity through this switch with a multimeter.  You can also temporarily connect the wires coming from the harness, thus by-passing the switch, to see if that solves your problem.  Note that if you do this, you’ll be able to drive with your sidestand down, so be careful.

When ignition problems arise, before you tackle your ignition system proper, be sure your “safety system” is working properly and:

Your battery is hot.  (“Hot” is approximately 12.6 volts)
Wiring is sound and connectors are clean
Your plugs are clean and gapped properly


We’ll now get into the ignition system itself.  The outline simple enough.  You start inside the left engine side cover, where two

PICKUPS sit near the rotor and produce a pulse of electric current when the pistons near TDC (Top Dead Center) which is fed to the

TCI BOX (Transistor Controlled Ignition, variously called the “ignitor box”, “brain box”, etc.).  This box has two basic functions.  It adjusts the signal from the pickups based on engine speed to change the timing as needed, and it cuts power to the primary winding of the

IGNITION COILS so that the secondary winding is “induced” to spit out a high voltage shot to the

SPARK PLUG WIRES and on to the

SPARK PLUG CAPS which in turn send it to the

SPARK PLUGS, where all this voltage (maybe somewhere between 10kv to 40kv-that’s thousands of volts) has enough pressure to make a small current jump the air gap between the electrodes at the bottom of the plug, thereby making a spark. This spark ignites the fuel mixture which, at that point is sitting all around the plug tip in a compressed state, ready to go BANG.

So that is basically what happens  But things aren’t quite this simple, and so we’ll take each element and talk about it in more depth.  We’ll also note the problems we’ve run into, the tests that can be made, and the repairs/fixes we know about.  Please understand I’m not a trained engineer or electronics guy.  My comments are based on what I’ve learned from reading, talking with people, and personal experience with the system.

To understand this system better, we will start by the discussing the coil.  It is the heart of the system, and once you understand how it works, the components/functions before and after it will be easier to understand.


The history of electricity and magnetism is a long and interesting one, with men in various countries doing experiments over several centuries and discovering bit by bit how electricity and magnets work and behave.  Out of all this work came two rules we need to understand.

Rule #1 Running electric current through a conductor (e.g. wire) produces a magnetic field around the conductor.

With the further understanding that
–A conductor fashioned into a coil yields a stronger field than a straight wire.
–A conductor wrapped around a metal core yields a stronger field yet, and turns the core into an electromagnet.  (As opposed to a permanent magnet which is metal with built-in magnetic properties.)

Rule #2 When a magnetic field moves through a conductor a flow of electric current (or potential) is produced in that conductor.

Several things need to be said about this:

A. It doesn’t matter whether it is the conductor or the field that moves. As long as there is relative movement between the two you get current moving in the conductor (or a potential for it to move).

B. For current to flow in a conductor, the conductor has to be part of a circuit. If the wire isn’t connected as part of a circuit, then the wire will just “want” to flow current (feel a “potential”).

C. Current running through windings of wire is what turns a coil into an electromagnet with a magnetic field. When this current is first introduced, a magnetic field radiates out (builds up) around the coil.  When the current is cut, the magnetic field collapses (goes away).  This build up and collapse of the magnetic field are felt as “movement” by any other conductor which sits in its path, and current wants to flow in that conductor.

4.The quicker a magnetic field moves relative to a conductor, the more potential (voltage) is generated in the conductor and the more current flows or wants to flow.

Using a combination of these phenomena, in 1908 an American by the name of C.F. Kettering, working for DELCO in Dayton, Ohio, described and patented the first automotive ignition coil, and that design is essentially the same one you have in your Virago today.


Virago Ignition Systems coils have two different windings (of wire) around the same metal core.  The PRIMARY WINDING is made up of a few turns of big wire and has low resistance.  This allows 12 volt current to flow through it easily, pushed by pressure from the battery.  This current returns to ground (negative battery terminal) through the TCI.  When this current begins to flow it creates a magnetic field which “moves out” from the iron core and turns the coil into an electromagnet.

But we also have a SECONDARY WINDING as well.  This consists of many (porabably thousands) turns of fine wire wound around the iron core usually inside the primary winding for dc coils.  It too, is connected to the positive side of the battery, but no current is flowing through it, since at its other end it is faced with “infinite” resistance in the form of the spark plug air gap.  The 12 volt push from the battery is not strong enough to jump the spark plug air gap and thus go to ground.  So there is no circuit.

The process is this: As current applied to the primary winding builds up and radiates a magnetic field out through the secondary winding, the secondary feels an additional push to run current.  But the movement of the magnetic field in the build-up phase is not fast enough to produce the level of voltage in the secondary strong enough to generate current that will be able jump the air gap. So there is still no “circuit”, and no current actually runs.

So…. here we sit with a nice fat current running through the primary winding, which in turn has built a fine magnetic field which now surrounds and cuts through the secondary winding.  Then the TCI suddenly switches off the current to the primary winding.  What happens?  The magnetic field suddenly collapses–moving much faster across the secondary winding than it did in the build-up phase.  This sudden motion of the magnetic field through the secondary winding is now fast enough to trigger very high voltage in the secondary winding due to its many turns. And these many thousands of volts are now strong enough to push current (small, but hot!) from this winding across the spark plug gap.  We now get our spark!  What’s left of this current and voltage after the spark then finds its way back through the cylinder head and frame to the negative side of the battery.  The current is so small that the high voltage is dissipated and doesn’t hurt a thing.

But how can the electricity from the secondary winding “jump” the spark plug gap when it couldn’t before?  Well, for you nuclear phycisist wannabees in the crowd, here is how I understand it.  Current is the flow of electrons, and if no electrons will flow you have an “insulator” and no current. The gas sitting in the plug gap is a good insulator.  Electrons are tied in tight to their atoms and are very hard to break loose.  12 volts is not near enough pressure to cause electrons in these gas atoms to leave their current atom and proceed to the next one– which is what current flow is.  30kv (thousand volts) however is powerful enough.  It now forces electrons into the reluctant gas atoms, which, in turn, have to give some up their own to the next gas atom. Current now flows. In short, faced with this high voltage, the gas atoms now turn from insulators into conductors, and current moves through them accross the gap.  Like lightning travelling through the sky, a spark occurs.

So that is my best shot on how the coil works.

Now we can start at the beginning and run through the whole system.


Pickups start the process by giving the TCI a signal to cut the current to the primary coil winding at just the right time.  Pickups are themselves little coils, but of a different kind, since they have permanent magnets inside the winding.  So a magnetic field is present all the time and doesn’t need a current flowing through the winding to create it.

Then on the rotor (flywheel) we have a small metal plate which passes very close to the pickup as the rotor turns around.  How does this non-magnetic “protrusion” (as Yamaha calls it) induce a shot of current in this coil winding? Remember that while this winding sits wrapped around a permanent magnet, current does not flow because there is no movement of the permanent magnetic field relative to the winding. Both are stationary relative to each other.

But now something called “reluctance” comes into play which can be likened to resistance in a conductor.  Magnetic fields “run” less strongly through the air (greater “reluctance”) than they do through metal which provides a more friendly path.  So when this “protrusion” cuts into the magnetic field radiating from the permanent magnet in the pickup coil, this magnetic field can “run” through this metal better (than through the air) and is momentarily strengthened.  As the magnetic field “fattens up” a little, it moves relative to the coil winding sitting around it. This movement is sensed by the coil winding, and a slight current flow, sufficient to trigger the TCI, is generated.

Sometime in the 90’s Yamaha changed from the two pickup system (one for each cylinder) to a single pickup system which works on a different priciple, sending out two different signals which are sorted out by the TCI.


As discussed above, current is fed from the battery (ignition circuit) through the ignition coil primary to the TCI where it goes to ground.  Upon receiving the pickup pulse, the TCI cuts off this ground connection momentarily which causes the sudden collapse of the magnetic field in the coil, as we have seen.  The TCI also senses engine speed and makes this cut somewhat sooner as the engine speed increases.

How does the TCI accomplish these things?  It does it with transistors and other electronic components.  When you open up one of these boxes you find a printed circuit board or two containing these components and connecting them in circuits.  I’m not qualified to explain just how these circuits work, and Yamaha does not describe the inner workings of TCI’s.  Trained electronic techs can understand them.


These are next in line, and we have discussed them above.


These are simply large, heavily insulated wires capable of carrying the high voltage current to the plug caps with a minimum of resistance.  Looking at a wire from an early Virago, we find seven strands of tin-plated copper wound together in a cable a little over 1 mm in diameter.  This is encased in a rubber insulator–the whole thing being about 7mm in diameter.

But there is more to these wires than meets the eye. As we now know when you run current through a conductor, a magnetic field around the conductor is created.  In the case of these wires, you have high voltage present and current flowing thousands of times a minute, and so a magnetic field, as well as the presence of high voltage potential in the air (electro field) radiates in and out from the wires when the engine is running.  These effects in turn create RFI (Radio Frequency Interference) which impacts am radio reception, and EMI (Electromagnetic Interference) which can raise hell with electronics, particularly those found in today’s sophisticated engine management systems.


In the Virago system, these caps serve two purposes.

–They connect the plug wires to the spark plugs.

–They also add about 5k ohms of resistance to this path to suppress RFI and EMI effects.

But how does adding 5K of resistance cut down on these effects? Well, it was not too easy to find someone who really knew, but here is the explanation I found.

As we have seen when volts in the kilovolt (thousands of volts) range start to push from the center electrode in the plug tip, gas atoms become conductors and the “infinite” resistance of the plug gap simply goes away.   What is needed is some resistance before the air gap to cut down the amount of current flow, that is, the amps.  With less current flow, the magnetic and the electro fields generated are smaller and less powerful, and so produce less interference for radios and electronics.  That, I am told, is why the 5K ohms are there and how they do their job.


Last, but not least, we have the spark plug.  A few quick observations:

–There are “resistor´ plugs that have resistance built into them, probably for the same reason that we find resistance in plug caps.  Viragos do not use resistor plugs.

–Tips of the plugs can vary in design.   ) as the standard.  These have the familiar nickel alloy center and ground electrodes. But new materials are coming on line (platinum, iridium) which permit smaller electrodes and are said burn cleaner and last longer.  They also cost a lot more.  Whether, on the low compression and low revving Virago, they make much difference, is a question.  You might try a set to see if you feel a little more power, get a little better gas mileage, etc. But if you’d rather spend your money on something else, BP7ES plugs will run your bike just fine, and should last a good 10K miles.

— Virago manuals specify NGK BP7ES as the standard plug for but later changed to BPR7ES plugs where the “R” stands  for “resistor”.  Since the coils and plug caps never changed I consider these plugs internchangeable.  .

–Plugs have different heat ranges. “Cold” plugs dissipate more heat into the cylinder head (which is also hot, but always cooler than the plug tip) than do “hot” plugs.  The lower the number, the hotter the plug. BP6ES plugs are one range hotter than the standard Virago plug.

The basic design tradeoff is this: you want a plug that runs hot enough to burn off carbon and oil deposits.  But you want a plug that will run cool enough so as not to burn up its electrodes (or suffer from something called “oxide fouling”), and thus have a short and unhappy life.  Or worse yet, start to glow and cause “pre-ignition” (pinging) which can damage the engine.  The proper heat range will encourage the plug to keep itself nice and clean, but also allow it to last a long time.

A good operating range for the tip of a plug might be between 450 and 650 degrees C (roughly 850-1200 F).  Starting with an understanding of the operating temperature range of the engine (which can differ significantly between engines), engineers specify a plug that will run within the desired heat range.  For Viragos that plug is the BP7ES.

One phenomenon that some riders experience is this: a cylinder fails to fires, or fires badly with the cap on the plug.  But when the cap is pulled just slightly off the plug and the cylinder lights up and runs.  Why would this happen?  Well, my best guess is that there is a problem somewhere in the system that is causing a weak spark.  By adding an additional air gap, the coil is forced to reach a bit higher voltage before the two jumps can occur, thus making for a strong, hotter spark.  The basic problem still needs to be found.

When riders start to foul plugs, a typical reaction is to try a hotter plug to burn off the built up carbon.  This really isn’t the way to go, in my opinion.  You shouldn’t be trying to solve fuel mixture or ignition problems by changing heat ranges.  Get your carburetion and ignition right, and run the right plug.

NOTE on the “Pressure Sensor”

With the introduction of the XV 1000 in 1984 a box called the Pressure Sensor was added, and is found on all 1000, and 1100 models..  This sits in front of your engine near the coils.  It has a vacuum input from one of the carbholders and several wires going to the TCI.  My understanding of its function is this: when the throttle is closed and the bike goes into deceleration, the increased vacuum activates a switch in the sensor which sends a signal to the TCI to retard the ignition timing–a smog thing.  These never seem to be an issue one way or the other, and I always leave them hooked up.

This concludes the description of the system.  Now we’ll look at:



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 Virago Ignition Systems 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

PICKUPS:  Yamaha

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 1000 Virago TCI ignition modules over the years!  That’s a lot of Virago’s saved from the scrap heap. 🙂 My current  charge is $125 which includes return shipping.
My web page location
My new email is
Thanks much,

David Denowh
617 Woodridge Drive
Rockford, Illinois 61108-2306

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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