No top end after rebuild

Jul 19, 2013
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...


Sponsoring Member<BR>Club Moderator
N. Texas SP
Nov 25, 1999
Sounds like the power valve is not opening.
Jul 19, 2013
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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