Hello all! I'm new to the forum and just bought my 1990 Suzuki gs500e the other week which is my first bike. Great bike except I just ran into an issue, when I drained the oil it was contaminated with fuel, I think this could be because I left my choke on and had the petcock switched to prime when the bike was off which I feel pretty stupid about. I also had a leaking crankcase cover gasket which I'm working on now. Will be posting more pictures in the future! Any comments as to why I might have fuel ending up in the crankcase would be greatly appreciated!

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Normally the gassy oil is from flooding. I had that happen when I was bringing mine home in a truck. My advice would be to clean out the carbs but the pros should be here soon to diagnose it. Nice looking bike by the way.

Thanks Joe! after draining everything I put a little bit of gas in the tank to see what happens and sure enough, after letting it sit for a while there was gas in the crankcase again (I also made sure the petcock was in the on position which is should be and the chose was off) so what ill do tomorrow is take out the carburetor and clean it out. Is there a certain way anybody would recommend to clean in? should I buy some carb cleaner or should I just take it apart and just clean everything off?

get 2 carb rebuild kits (each does one carb) they're cheap...that way you'll have all new seals/etc...otherwise yes carb cleaner and a toothbrush

Thanks robtech, I'll look into getting those carb rebuild kits, the guy that sold the bike to me said that he already rebuilt them but if I'm having these problems that something clearly went wrong haha. I'll take it apart tomorrow and check all that seals and everything and most likely will take pictures for all to see. My next concern is that petcock that seems to give everybody problems, should I replace the side mounted one with a manual shut off valve or get a different vacuum valve because from what I understand, if the engine is off, there should not be any fuel even being delivered to the carbs unless the petcock is in the prime position which it is not.

If he says that the carbs. have been rebuilt, make sure that you double check the float height to make sure that they're closing when the bowls are full.  I haven't worked with the petcock much, but I think your line of thinking is solid.

I really dig your bike.  That black/grey color combo is excellent!