Checking if fuel has gone into oil

[MaxCannon]

I'm sure I've read somewhere that if a bike with carbs falls over while the motor is running there is the potential for fuel to mix with the oil in the sump.

I talked to my dad who is a mechanic about it and he didn't seem to think it would happen (unless the piston rings were already in such a state that it would happen while the bike was upright anyway).

So - assuming a healthy motor, and assuming that my cat like reflexes (which didn't stop the bike from falling off the stand while I was opening the driveway gates) hit the kill switch a second after the bike was on the ground - do I have anything to worry about ?

The oil looks fine and smells pretty normal - is there a sure fire way to tell if there is fuel in it ?

[PeterD]

I think you should be ok. While the bike was on its side you might have had fuel leak from the carbs via the bowl overflows as the floats would not be operational but as for fuel getting into the oil, I don't think so.

[Ixion]

Only an issue if the bike is on its side for a long period. Days, weeks. With the fuel tap on. The process is that if the fuel is on and the bike (and thus carb ) on its side, the float mechanism does not work. there may be a constant flow of fuel into the carb. Normally, it will just leak. But if the angles are right (wrong) it may leak into the inlet tract and past an nopen inlet valve into the cylinder. Once enough fuel has entered the cylinder it will start to seep past the rings into the sump.

But all this takes time. A lot more than a few minutes.

It will happen whether or not the motor is running - though if the bike has vacuum operated fuel taps, a non running motor should mean no fuel flow.

And of course it will not happen on an injected engine.

[MaxCannon]

Sweet - hopefully this helps out some other bikers too.

Of course the best advise (which I thought I already learnt the last time I tipped over my old bike) is to make sure the stand is actually down firmly before you get your bum off the seat.