Motorcycle Repair: oil all over, cb 750, muffler

Question
I just bought a 74 cb 750 rode it twice and oil is coming out of the left muffler, bad enought that it is getting on tire and making it slick. The guy said the motor was just rebuilt a few years ago but has sat for a bit only rode a few times past couple of years.  Do you have any idea where I should start or what might cause this?

Answer
Are you sure it's coming from inside the muffler and not from a breather hose near the muffler?  If it's coming from inside the muffler, you have a bad piston or cylinder allowing oil to get into the cylinder and get pumped out the exhaust.

Regards,
Rich