Motorcycle Repair: 1982 Kawasaki CSR 250, float valves, petcock

Question
The bike had 2700 miles when I bought it. Had some expected problems with the carburetor (old gas-varnish) solved those, but now the transmission slips.It's rideable as long as I don't get above 3500-4000 rpm...The petcock is stuck in the "on" position. Is it possible I have gas mixed with the oil? Do the engine and transmission use the same oil?

Answer
You can sometimes smell the oil and if it has gas it will smell like gas. The old float valves have o-rings which may need replacement if there's gas in the oil. There are petcock rebuild kits for many models. Even the best float valves may leak a little so leaving the petcock ON continuously is not a good idea.

These bikes all have wet sump clutches which share oil with the engine. Make sure you change out the old oil since running the bike with gas in the oil is not good for the motor.

Ofcourse, the problem may not be the oil at all. It may just need a new clutch.