Re-using powervalves??

[jds535]

Hi Guys,
I am rebuilding my sons 1999 YZ125 and have a question for you. First some history.... I bought the bike as a basketcase, topend was shot. Bottom end was worn. The cylinder was sleeved so I sent it out to be bored. The shop bored it out to 56mm. He also said he had to cut the powervalves to fit the new bore. My son ran it all summer and the bottom end just went and took out the topend.
I am rebuilding both now. I bought a new crank kit, and a new topend kit including new cylinder. My question is, can I use the powervalves ( machined to 56mm bore ) from the old cylinder, or do I need to buy new ones. I have a lot into the motor at this point and the powervalves cost about $500, thats more than the whole topend kit. My guess is that it would be Ok t use them, but I would lose some bottom end power. I dont want to spend all of this money only to have a gutless motor. Any thoughts?

 

[arnego2]

yep

As a educated gues I'd say yes you could. You have to retrim the PV anyway over time they sing deeper. I used my "old" PV OEM from 2009 in my new Cylinder (2012) and they have been trimmed, I felt no differences but the trimming was just about 1mm.

 

[jds535]

Got everything back together and got it running. It rips on top. Feels a little rich in the middle. We are gonna run it for a bit then check the plug and go from there.