During the valve adjustment, we noticed that one of the exhaust valve lifters has a circular pattern of indentations on top, and the corresponding lobe of the exhaust cam has a groove indented in it.
It seems as if the valve spring is broken or damaged and the cam hits the lifter at the wrong place and time.
All other lifters and cam lobes are good.
The valves clearances were within spec, and oil has always been changed regularly with synthetic. And the bikes runs good.
Has this happened to any of you? What did you do and what happened?
Could that be a defective spring on the exhaust valve, since all the other ones are fine?? Can it be a problem from Yamaha?
Any ideas appreciated!
Edited by wr450man, April 05, 2013 - 07:18 PM.