Maintenance & Technical > KX500 Original

First top end rebuild. Help needed

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Richyb83:
Hi, just to put you in the picture, I'm a pretty novice rider and I'm carying out my first top end rebuild on my sh kx500af the motor has done around 40hrs and is still on stock bore and piston, there is no scoring or flaking on the barrel but she does look a bit thin around a few ports, Ive bought a wiseco piston rings and top end bearing along with new head and base gaskets, I've cleaned and decoked the main powervalve parts and I'm just waiting on the barrel to come back from the platers. The main reason I stripped it down was that I noticed I was losing water only when it ran and not through heat, basically the head gasket had failed and was allowing compression into the water jacket. It never leaked when stood so I don't believe water ever entered the bore.

Does anyone have any suggestions or handy tips on rebuilding it including power valves and gaskets (does anyone use any extra sealant on head gasket etc?)
Is there any prep work worth doing on the barrel pv or piston/ rings before I rebuild and what ring end gap do you guys suggest?

Thanks in advance!

Motorrad:
Wiseco rings won't work on cast pistons.

And have you read this?

http://www.hallbergs.net/kx500/

Richyb83:
Sorry I made a typo it should say wiseco piston & rings! :-D

Just has a look! That's an awesome help! Cheers

I'm off after an ankle opp (destroyed it a year ago the first time I rode my 500 and tried to ride it like a 450!) and have plenty of time to get the whole bike refreshed nicely. Want it back like new again. Pretty much going to only be the frame untouched.

bjohn07:
im gonna be watching this one.  got a rebuild due nxt winter.    post a lota pics.

Motorrad:

--- Quote from: Richyb83 on January 31, 2013, 12:13:00 PM ---Hi, just to put you in the picture, I'm a pretty novice rider and I'm carying out my first top end rebuild on my sh kx500af the motor has done around 40hrs and is still on stock bore and piston, there is no scoring or flaking on the barrel but she does look a bit thin around a few ports, Ive bought a wiseco piston rings and top end bearing along with new head and base gaskets, I've cleaned and decoked the main powervalve parts and I'm just waiting on the barrel to come back from the platers. The main reason I stripped it down was that I noticed I was losing water only when it ran and not through heat, basically the head gasket had failed and was allowing compression into the water jacket. It never leaked when stood so I don't believe water ever entered the bore.

Does anyone have any suggestions or handy tips on rebuilding it including power valves and gaskets (does anyone use any extra sealant on head gasket etc?)
Is there any prep work worth doing on the barrel pv or piston/ rings before I rebuild and what ring end gap do you guys suggest?

Thanks in advance!

--- End quote ---

Okay now that IM on a computer and not my phone..

1. Use Cometic gaskets.
2.  CHECK piston/wall clearance... going from cast to forged can cause PROBLEMS (Ask USMC500 about that one... thats the reason he didnt get to ride his bike for many years)
3. ring end gap..   most wiseco rings come in anywhere from .018-.024"  striaght out of the box.       MINIUMUM should be .0135" for a stock 86mm bore

4. HOw many years since it has had crank seals??

5.  read some more motor build threads on here...   (mine included)   TONS of nifty tips and tricks to be found

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