No top end after rebuild

Jul 19, 2013
5
0
#1
Just completed a bottom and top end rebuild on my 2005 kx125. The problem is, it has good bottom-to-mid but now (after the rebuild) has a very mediocre top. Some history: This is my 5th rebuild so I thought I would go all the way and have the cylinder replated by MaxRPM and had them match a Wiseco ProLite piston. Also put in a new Hot Rods crank/rod combo since she is getting old. Now, the bike starts on first kick, pulls off the line good but mid-way-up, acts like she just applied for Medicare. This bike used to have incredible top end and would rev to the moon. Now it's just another 125...or less. I wonder if MaxRPM gave me someone else's cylinder ? Another question, the piston they gave me was much tighter than the one it replaced (unfortunately, i didnt mike it). Could the piston be too tight? I didn't change the jetting or anything else. It has VForce reeds and a ProCircuit pipe. Any ideas would be appreciated...
 

BSWIFT

Sponsoring Member<BR>Club Moderator
N. Texas SP
Nov 25, 1999
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www.dirtrider.net
#2
Sounds like the power valve is not opening.
 
Jul 19, 2013
5
0
#5
Sorry for the delay. Actually the problem was the machine shop had it set up too tight. Broke a ring after only 9 hours on it. Changed cylinder replate shops. They set piston to cylinder clearance at factory settings. The other shop had it set up at only 1 thousandth if I remember. About 1/2 min. (I think factory is 2 1/4 thousandth). Moral of the story: check to see if it meets factory clearances when you get it back before putting back together.
 

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