Motorcycle Repair: 1983 Yamaha 750 Virago, 750 virago, riding habits

Question
I started out painting my buddies '83 750 Yamaha Virago then he told me about his other problem. Since it's partially stripped now is the time to look at it. He says that after 20-30 miles the front cylinder will foul the plug. After changing both plugs it runs fine for days. He also said that the tach quits just before this happens. I'm scared its the cid but I'd like your opinion on it before I do anything.
                      Thanks,
                      Bill Hardesty

Answer
Hi Bill,

The fouling may be attributed to a person's riding habits, improperly use of choke, carburetor detuning, restricted air flow, or ignition (CDI) problem.

Riding Habits: Does the rider lug the engine around or does he stay within the power band?

Are the correct plugs in uses and properly gapped?

Is cylinder compression and valve clearances within serviuce limits? Both are important for proper carburetor operation.

You may call a local Yamaha dealer and inquire if they can test the CDI and ignition system.

Send me an email address as requested. I'll return a few information files that may help you guys diagnose the problems.

My email is: mshively1@woh.rr.com

Respectfully,
Mark Shively