removing stuck oil drain plug on yahama big bear 350

[kitchenguy]

This 350 big bear is from the 80's and has gas in the crankcase, we believe from a badly flooding carb, which has been since rebuilt. When atempting to start it runs fine for a few seconds , then gas mixed with oil comes from the breather hose on the engine up to the plastic air tube the goes to the air box. Tried to remove the 19mm drain bolt with no success, the bolt head is starting to get rounded. Any tips??
Thanks in advance

[CJM]

Heat, apply a torch for a min or two and then try it. If you can get it loosened a bit heat it again and take a candle and stick it as close as you can to the threads as well, will lubricate it.

[kitchenguy]

Thanks for the reply, though with the case filled with gas I didn,t feel heat was a safe option.

[450R NOOB]

Well if it does round off, use a dremel tool and cut a thick notch in the bolt that you can stick a file or similar tool in to turn it. How I always deal with rounded off bolts and what not. I think heat is the only way to help it come out other than a hammer or cheater bar.