Top end replacement...yes, here we go

I would rate this at around 8 out of 10. I have changed so many pistons over the years I've lost count, I think I could do it blind folded. So why don't I rate this lower? There are many issues that can lead to problems when rebuilding your top end if you have little experience. For example, you may not be aware of the tightening sequence for the cylinder or cylinder head studs, you may install the piston backwards, you may not install the gudeon pin retaining clips correctly, you may not adjust the powervalve actuator correctly. Any one or any combination of these mistakes will lead to poor performance or severe engine damage. Despite the fact that I feel I could give you a step by step guide here in this thread, I also think that there is allot of information that would be specific to your model motorcycle. Therefore I would suggest that you purchase a workshop manual before continuing with this exercise, I guarantee you will not regret it.

Take the cylinder out to see what you did. Did it cease? Or just doesn't have any compression?

Ok sorry if my remarks seemed like you were clueless, that was not my intention, I was hoping to give you a heads up on issues that people I know have experienced on various motorcycles. I don't see why you would not be able to complete a rebuild, but be sure to follow the instructions in the manual well, if there is anything you are unsure about post the question and I'm sure you will get help. As the other guy suggested it may be best to strip part of the top end to diagnose your issue.You are going in the right direction, checking compression is a good idea, next try looking for another cause of low compression, for example remove the expansion chamber and look at the condition of the piston through the exhaust port. I'll tell you quickly about an issue I experienced recently. My bike began to run poorly, after realising that it was not the obvious eg. fuel, electrical etc. I decided to remove the exhaust and look into the exhaust port to see if I could get a clue to what was causing the problem. As I moved the piston down the stroke to expose the piston crown I could see that the top ring and the rim of the piston were scored. I could then see that the piston needed to be replaced.

wiseco
and if you are smart about it the job you are about to do can be a 1 out of ten

but.....be smart pay attention to the smallest details