Yamaha Virago Tuneup

The thing about a tune-up is, you likely don’t need one. If your bike’s running strong and true, just change that oil a lot (and some of the other fluids now and then as well) and enjoy your career as a Virago rider.

But there will always be a few folks who think they need a Yamaha Virago Tuneup, and maybe they do. “Bike’s not running quite as strong as it should. I guess it needs a tune-up”. We hear terms like “major tune-up” and “full service”. But, what does “tuning” the Virago really mean? When you take your bike to the dealer and say “I think it needs a tune-up,” what specifically should the dealer do? Or, what should you do it you are going to attempt it yourself? Her is my cut at an answer to these questions.

Before we get going, we should note that the various elements of a tune-up don’t necessarily happen all at the same time, and might better be thought of as separate procedures. If you changed your plugs 500 miles ago and did it right, you wouldn’t do it again just because you decided to check your carburetor settings. You will note in the recommended maintenance schedules that different procedures have different time intervals. So the following group of procedures may be thought of as a tune-up.

The first thing we do is what we did with our old cars, change the plugs, install a set of points and then set the time. Rich? Wrong! There are no points on the Virago and the ignition timing is preset, that is, not adjustable. The ignition advance is controlled electronically by the TCI unit, sometimes called the “ignitor box”. While ignition timing and advance can be checked with a strobe light, unless you suspect trouble there is little reason to do this. If a problem is identified, you’re still not adjusting anything – you’re replacing parts or maybe checking connections. While you do need a strong, correctly timed spark, there’s just not much to “time” here.

Plugs are another matter. Changing the plugs was always part of a tune-up, and it still is. New plugs should be fitted at the called-for intervals or if they become excessively dirty or fouled. In these latter cases, you’ll want to find out the reason why this occurred. Most owners should be able to handle the plug-changing chore without too much trouble.

Well, then, how about the valves? As part of a tune-up, the adjustment on the valves should be checked and if found to be out of spec, reset. This procedure is one that the enterprising Virago owner can learn/master if he/she is so inclined. The factory service manual is the best source of information on how to do this. The Clymer or Haynes manuals also cover this.

That leaves the carbs. There are three things that can be done with the carbs. First, the richness of the idle and low rpm mixture (controlled by the pilot circuit in the carburetor) can be set. Somewhat oversimplifying, there is an “ideal” ratio between fuel and air which results in the best and most powerful burn. The term “rich” means more fuel to air, and term “lean” means less fuel to air. Richness/leanness is typically measured by the percentage of CO (carbon monoxide) present in the exhaust gas – more meaning richer, less meaning leaner. CO readings are changed by turning the pilot screws in and out. Viragos come from the factory these screws are blocked by brass or aluminum plugs so that you can’t get at them. The reason is that fuel flow rates have been set to EPA standards (on the lean side) at the factory and are not to be changed. Most Viragos run very well on the factory settings, and if yours has good power you should probably leave well enough alone.

However, for those of you who cannot leave well enough alone and are ready to risky heavy fines and imprisonment, these plugs can be removed and the CO settings adjusted a tad richer for quicker warm-up and better low-end performance. Also, if your carb was set at the factory last thing Friday afternoon when the country music station (and they have them in Japan) was playing “Take This Job and Shove It”, these screws may not, in fact, have been set correctly. We have seen several cases of this.

It should also be noted that pilot screw settings may absolutely need to be changed due to outside circumstances. For example, if you move from sea level to a new home in the mountains, you will want to screw the pilot jets in a scosh, because a bike set up for sea level will run rich at 5000 feet – the fuel supplied is the same, but the oxygen is less. Also, you should always check the CO after installing aftermarket pipes, since they may lean out the low-end mixture. More air (oxygen tends to be available because of lowered back pressure in the freer flowing exhaust pipes.

What should the CO be? Three to four percent comes to mind as the range for test performance. But your emissions will be a tad dirtier. Stock, your bike will almost certainly be down in the one to two percent range, and it has been designed to run just fine there.

How can we measure CO? Very tough for the average home mechanic. Many Yamaha dealers have the equipment to do it. You’ll notice little belts in your headers. These are removed and the CO probe screwed in or inserted. Dealers may be reluctant to remove the plugs covering the pilot screws, but should be more willing to set your CO to where you tell them if the plugs are absent. Removing plugs can be tricky, by the way, and must be done with great care. You typically wind up drilling them and as the drill exits the bottom of the plug it has a tendency to get sucked through and crash into the top of the pilot screw, buggering it.

Automobile-type CO meters that you stick into exhaust pipes are available for around $150 from J.C. Whitney, and work quite well, but it is hard to use this type of meter when both headers are pouring into a common box, as is the case with the stock Virago exhaust system. Since exhaust gas from both cylinders is mixed and exits both pipes, you can’t tell the individual settings of the carbs. Fit individual pipes (Jardines, Cobras, etc.) and you’re in business with one of these meters because now you are reading each cylinder individually. There is also a gizmo called a Colortune Plug which allows you to see the color of the burn inside the cylinder. Think of your water heater. Orange means too rich, and blue means good. Amazing as it may seem, the same rules hold true inside a motorcycle cylinder as well. Yellow means too rich, blue is good and light blue to white is lean. Honest! The trick is to be able to see what’s going on in there. The Colortune Plug replaces the spark plug and has a transparent window around the electrode which allows you to actually see the burn. You can adjust the pilot screws to get a nice fat blue (just off orange) for good performance.

Finally, it is well to note that these pilot screws are mixture screws not air screws as they are often and wrongly called. Turning these screws in reduces the available mixture (fuel) and leans the carburetor. Turning them out provides more fuel and thus richen it. This is just the opposite from air screws, where turning the screw in cuts off air, thus richening the mixture.

Well, assuming that we have our pilot circuits under control, we do need to synchronize the carbs. Simply put. Synchronizing the carbs get them providing fuel to each cylinder at the same rate, so that one cylinder is not working harder than the other. All the manuals cover this procedure. It is easier to perform on newer Viragos, since on the older Hitachi carbs the synchronizing screw is tougher to get at and the linkage between the carbs can also be a problem. Synchronizing the carbs requires a measure device, and mercury sticks are the gauge of choice these days. They measure the vacuum in the carbs, and are accurate and easy to use. They cost around $25 to $40.

Finally, the easy one. Set your idle to the proper number, usually 1,000 rpm for Viragos. This is done with the little wheel screw located on the right hand carburetor.

The above represents about all I know to do to a Virago under the general category of “tuning”, but three other things are worth mentioning. First, the air cleaner should be serviced to be sure that carbs can breathe freely. Second, make sure there are no problems in the fuel system, which might restrict flow. Is your fuel filter clear, your vacuum-operated petcock (if you have one) working properly and your fuel tank breathing normally? Air and fuel are where it’s at and your carbs must have a full compliment of both to function well. Finally, in cases of bad running, where the causes are not to be found, a compression check may be in order.

As noted earlier, the electrical circuits involved in ignition are usually working properly, since if they are not you’ll know it soon enough in the form of a missing or dead engine. Most electrical components such as coils don’t fail, and in the rare case that they do, they are usually dead gone and tests will show this. TCI units are another story. Sometimes they develop intermittent problems that can be mistaken for carb problems. This happens mostly on older models, and the only test is to install “a known good one” and see if the problem goes away. But generally the electrics are OK and optimum performance is achieved by paying attention to the areas cited above.


        If you are serious about tuning and maintaining your Virago yourself, invest in a factory manual. If you take your bike to the dealer for a “tune-up”, don’t be afraid to ask what procedures will be included, or better yet, tell him specifically what you want done. Here is a quick checklist:

Change plugs:
·  Adjust valves
·  Adjust carb pilot screws (set CO)
·  Synchronize carbs

Set idle:
·   Service air cleaner And if you suspect trouble, Check ignition timing
·   Check fuel delivery
·   Check compression

Virago Tuneup Submitted by Mac McCurdy

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Rev. 1/06
Note: This Tech Article was created from the VOC site data.(Virago Owners Club)

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