Compression good indicator of top end condition?

[Dogz]

I was just diggin into the kdx for a top end rebuild as I have no idea when or if one was ever done! I decided to do a compression test for a before and after comparison. Mine currently has between 200 and 205 psi, Manual says 145-220 psi is good. I tested a few times just to be sure.
Is the only real way to tell to keep ripping it apart and measure bore,piston, ring end gap,etc.
Or should I be happy with 200+ psi compression and leave it alone?
I'd rather put the money into gold valves + new springs.
Thanx for info about wiseco pistons.
Are wisecos manufatured to take into account the extra clearance required?
Say I need a B sized piston from Kawi, would the B or next size up from stock wiseco be what I need?
Thanx Again

 

[m0rie]

If your compression is at the upper end of the service limit then your top end is most likely just fine. If this bike is still new to you I still tear it down and check everything out. If nothing else take off the head and clean out the kips ports and valves. They get covered in carbon very easily. Wiseco pistons come in one stock size 66mm. They then go in 1mm overbores. This is different than the pro-x pistons which are sized to the OEM bores of A-B-C-D-E. So if you get a wiseco you get the standard one (66mm)

-Maruice

 

[Braahp]

I'd be way happy if my compression was that high. Are you sure thats right? You know all guages excpet a Snap On are useless huh? Regular guages you buy at auto parts stres are not accurate. Still..............I'd say your top end is fine.

 

[Dogz]

I'm sure the guage is correct, it a high quality thread in one. I tried about 5 times held the throttle wide open and kicked it over until the reading wouldn't go higher.
I pulled the top end anyway, the previous owner must have had it serviced not to long before I bought it. Everythng was well within spec.
The KIPS was pretty clean but I wanted to check it I'll clean it anyway. Now I get to put on a '88 thin head gasket and a new base gasket. Now I get gold valved instead of a piston kit!!! WooHooo

 

[m0rie]

a '88 thin head gasket

Are you sure you can do that? The 89-94 motors are completely different (watercooled) than the 88 and earlier motors.

-Maurice

 

[Dogz]

Should have said 88 kx 250 head gasket. Its 20 thou thinner than the kdx gasket .026 vs. .046

 

[m0rie]

Should have said 88 kx 250 head gasket. Its 20 thou thinner than the kdx gasket .026 vs. .046

Ah, missed the fact that you've got a KDX 250, not a 200. Doh! My mistake.

-Maurice