Motorcycle Repair: not sure where to start?, fuel air mixture, piston rings

Question
I have a 1982 yamha seca 400. The bike starts up and only runs on the left cyl. if I rev it up, the right side kicks in and stays kicked in. Also when revving it or driving it, it has endless power in every gear, it runs great! however I found gas in the bottom crank with the oil and it blows a little white smoke? I was thinking piston rings need to be replaced? ( seeing as how gas is getting down into the crank somehow ) Or could it be strictly a carb issue seeing how it seems to be running fine except start up and the smoke.any suggestions?

Answer
There are a few things to check, one of them is to drain the float bowl of the right side carb to get rid of any contaminated fuel. A carb synch might be helpful, as the idle screw may have backed off and the right cylinder does not get enough fuel/air mixture at idle.

White smoke in the exhaust is usually caused by excessive water in the fuel system. Gas in the oil is usually caused by a stuck carb float that does not shut off fuel flow from the gas tank when it is not required - when the motor is stopped the gas will seep into the cylinder and past the piston rings, then down into the oil supply.

If the piston rings were worn you would see lots of black smoke from the exhaust, so I think you're okay on this one. I would suggest draining the right side carb float bowl and check the float needle for debris first, then do a carb synch to make sure both throttles are opening at the same time.