Should I redo my top end?

[sillygoose27]

I've been thinking about doing my first top end on my bike. '87 KDX. It runs great and I have no problems with it at all, its just that I've had the bike for 2 years now and have never done the top end on it. I ride mostly woods, but open it up once in a while on some dirt roads. It gets a ton of hours on it when i can ride it, which isn't often, but i'd say probably about 125-150hrs since i've had the bike. I don't think the guy I bought it from had done it in a while either. I'm just a little worried about tearing it down and it not really needing it. Just wanted some opinions on what i should do. I guess a little money spent now, is a lot saved later.
Gregg

 

[harryhuia]

Have you done a compression test?
A KDX's top end usually lasts a long time.
I would suggest just checking your top end, the only real cost in that is gaskets.


Ben

 

[Dogz]

Just did my 250, I was in sort of the same situation, second hand bike, not sure of the history.
I had about 200 psi compression, took it all apart measured it all.
Cost me 35$ Cad. for gaskets, thats cheap peace of mind though.
I'll do a piston next winter.
For a MX er they say do a piston about every 25 hours, If you've done hundreds of hours and the previous owner did I'd check.

 

[dsndblm]

I rebuilt the top end on my 88 2 months ago. The cylinder bore measured good, the rings were a worn some. The top end had never been done and the bike has hundreds of hours on it. The only problem I found was the power valves, they were almost completely closed with carbon. It was well worth the time and money to freshen it up, runs like it did when it was new.

 

[harryhuia]

Motocrossers don't do a piston every 25hours. But rings every 25hours.They do their piston next time.
(that's what my neighbour, who is a retired motorbike mechanic, said)


Ben