My son has a 2004 yamoto 150.We got it last nov. and now its smoking and fouling plugs big time.I assumed it was rings so i have some on order but when i took off the cylinder and checked evrything out the rings seem to be in good shape,the cylinder is smooth,no burns or gouges,but the evidence of burning oil is there, the top of the piston and the valves are really carboned up.Does this still sound like a ring problem even tho there is no evidence of the rings being bad?

 

I would be curious as to what the ring gap is. The rings could be worn with a smooth cylinder. Only other way for oil to get in is thru the valve stem seals.

 

Hey yeah,valve stem seals, didnt even think of that 1 thanx

 

Your welcome.