Motorcycle Repair: 1981 Yamaha 750 virago (clutch slipping), clutch discs, friction pads

Question
Hello Mike, just trying to get some input on my problem with the 1981 Yamaha 750 Virago. It runs great, but i notice if i give it a lot of throttle quickly it seem to rev slightly (like slipping a bit) but i can ride it at highway speeds for as long as i want and it is fine.  It only seems to slip if i give it a lot of throttle quickly, otherwise if i just ride casually it is great. Thanks for any advice you may have.

Answer
Yes, it sounds like the clutch is slipping and is in need of adjustment. When you whack the throttle, it places a large and sudden load on the clutch plates and if they are not set under the correct pressure, they will slip until the motor speed catches up to the throttle input. A clutch free play adjustment should cure the problem, unless you have many miles on the bike, in which case it may also need new clutch plates.

One other possible cause of slipping clutches can be traced to what type of oil is used in the motor. The clutch, transmission and motor on many Japanese bikes use the same oil. If you are running an automotive oil instead of one specifically formulated for air cooled motorcycles, you are heading for disaster. Automotive oils contain friction reducing additives that will destroy the friction pads in the clutch discs, causing them to slip more than required. Eventually, these additives will render the clutch discs useless and they will need to be replaced.