Motorcycle Repair: Oil and Gas Puddle, honda cb350, gasoline vapors

Question
Hello,
Recently I purchased a 1969 Honda cb350 (running) I have ridden the bike a little while. But just this weekend I cranked it up and engine idled without a problem. After revving it a few good times I suddenly noticed an oil and gas mix being shot out from the "exhaust hose" attached to top end of the motor. I also noticed a sudden increase to response on the throttle and power. What does this indicate? Please help!  

Answer
ARt, the hose attached to the top of the engine is a crankcase breather hose, to allow excess fumes to vent, preventing crankcase pressure from building up and pressurizing the engine seals, which cause them to leak and in some cases, blow out of position!

Oil fumes are normal, but having gasoline come out of there is not! The main causes of that happening would be that gasoline has gotten into the crankcase through the carburetors. IF you don't turn off the petcock and/or it leaks internally, the gasoline CAN fill the carbs, overflow and then drain down into the intake valve, into the cylinder if the valve is open and then drool past the rings into the crankcase. On a CBX six, this will cause the rods to hydraulic and bend... not a pretty picture.

The other way gasoline vapors could be noticed is if the engine is running rich or the choke is being left on too long and the rich mixture isn't fully burnt in the combustion chamber. With somewhat worn rings, the excess gasoline residues will work past the rings into the crankcase.

I would suggest checking the oil and perhaps changing it to get the gasoline out. Check the petcock for shutting off fully and notice if any carburetors are dripping at the float bowl overflow tubes. This could indicate leaking float valves or the seats, which are sealed with O-rings that fail over time.

These old twins need careful tuning and adjustment of the points for accurate ignition timing and a check of the mechanical spark advancer behind the point plate. If it sticks then you can get performance problems, like erratic idle and acceleration issues. After that the carbs should be checked for synchronization, as well as float levels and O-ring integrity.
This all assumes that the engine has good compression on both cylinders and that the valves and camchain tensioner are adjusted.... Basically a full tune-up first, then check for problems beyond that.
Your sudden increase in power may be a spark plug clearing itself from being fouled.
Bill Silver