JamesC 4 months 16 days ago Location: Port Colborne, Ontario
Own a 1996 yamaha virago+750cc--can the Mikuni carbs be adjusted for air-fuel mixture-I was told that they often are factory set and can't be adjusted?
the problem is one plug burns really clean and the other burns as though it is running rich--black soot. changed plugs, burn a hotter plug on the one side, checked choke cable--will check air filter?? thinking I may have to rebuild the carbs--any suggestions--thanks for your help--JIm
MotoSport Staff 4 months 15 days ago Location: Portland, OR, USA
Yes, the carburetors can be adjusted for air/fuel mixture. They need to be internally re-jetted for large changes, but small changes can be made with airscrews located on the engine side of the carb, just above where it slide into the manifold. Before doing any modifications, you should start with a carburetor rebuild followed with having the carbs synchronized. Once they are synchronized you can set both air screws at 2.5 turns out from a soft seat, then start with the rear cylinder and turn the pilot screw in until the engine starts to falter, then back out until it idles smooth, then 1/4 turn more. Repeat this with the front cylinder. If the bike does still not run correctly you may need to modify the actual jets in the carburetors. The jetting can and will vary based on any intake or exhaust modifications done to the bike also.