I have a 1975 Yamaha rd 250, its a great little bike and it runs alright though it tends to give white smoke out of the exhaust and gets the spark plugs very oily. Because of this, I suspect a bad head gasket; and a gasket kit for the bike isn’t incredibly expensive or anything but I’d like to know how to check to see for myself if it actually is the gasket, and not just the wrong oil pump adjustment or something. Please help!

And is there a gasket behind the oil pump?

Seller says it is a valve cover gasket. He said it shrunk over the winter from non-use and will ‘heal’ when the bike is used and warmed up. Does this sound right to you? What would cause the oil leak,( quite a bit of oil!)?
The bike is supposed to only have 4000miles on it.

Turning a 2006 r6 black motor into a 636 r6, need a 2mm head gasket, where can I get one?