Motorcycle Repair: 81 Yamaha Virago 750, combustion chambers, yamaha virago 750

Question
I recently purchased a 1981 Virago with about 30,000 miles. I am having problems with what I believe to be the carbs. The bike starts and runs but it smokes excessively and really is not running smoothly, I am wondering if the mixture setting is off or what. When I bought the bike it came with a rebuilt set of carbs which I installed but I am not completely sure of the quality of the rebuild because I don't know where they were rebuilt.   I really don't want to just start guessing so I hope that you may be able to shed some light on the situation.


Answer
Hi Chad,

First thing to do is obtain a service manual for this MC. The manual contains procedural and spec intel needed to perform service. It will pay for itself with the first repair.

Next, perform a cylinder compression check and a leak-down check if necessary. These two tests will determine the sealing properties of the combustion chambers (condition of engine) and locate the source of compromised seal. Compare results of tests with service limit specs in manual.

Visit Bike Bandit's and Yamaha's websites to view parts microfiche on line.

www.bikebandit.com
www.yamaha-motor.com


I need to inspect the carburetors to offer opinion on their condition and what may need to be performed to restore proper performance.

If you send me an email address, I'll return numerous files on carb cleaning, tuning, and synchronizing.

Respectfully,
Mark Shively