Oil in crankcase?

[lovetoride]

Hello everyone, finally a place where I can talk and talk about bikes!!!

But first, I need everyone's help, with thanks of course.

Why would I have gas in the crankcase after riding. The bike did sit up for awhile and I thought all was OK until recently.

This is what I done the first time I found the gas in the crankcase:

drained all oil, replaced oil filter, refilled crankcase with oil to normal level, checked oil level before riding, checked level after riding, level is higher.

Thanks for having me and any help would be most appreciated.

[Gummiente]

Welcome to TMW!

If the fuel tap has a weak diaphragm spring or a punctured diaphragm, fuel will continue to trickle down into the carb even though the motor is shut off. The carb will overfill and the excess fuel then follows gravity's path and flows into a cylinder (most engines will come to a stop with one intake valve partially or fully open); it then seeps past the piston rings and down the cylinder walls into the crankcase.

[Wrider]

Yep exactly what Gummi said.

[Gummiente]

Also, if the fuel tap is left in the "PRI" (prime) position instead of "ON", it will do the same thing, as this setting bypasses the shutoff diaphragm.