Two Stroke Motocross
Two Stroke Motocross Forum => General Two Stroke Talk => Topic started by: coblefutch on August 11, 2011, 11:21:23 AM
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Early this spring I picked up a clean 05 yz, the guy I bought it from had recepts from his local yam dealer showing the top end was rebuilt just a few weeks before. The bike had good compression and ran strong. I had been riding an xr 400 so the yz felt like a beast. I rode it through the summer.
Raced in 5 local woods races. loved the bike but it always seemed kinda soft on the bottom. t weeks ago i got a chance to ride a buddys yz125 and it had more grunt and low end than my 250. hmmm. I figured my rings were shot as I guessed I had about 80 hours on the top end.
Pulled it apart and the piston and rings were nearly in spec, bore looked good. Then I looked at the POWER VALVES, the guy at the dealer had installed the 2 valves for the side booster ports BACKWARDS with the slot facing inside. This held them in the open position and bound them up in the cams that operate them effectively locking them in the full open position. Put the valves in the correct way and got them to operate correctly, installed the fresh Wiseco. After a proper break-in, WOW its like a whole different bike.
Check a used bike out real close.
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Glad you got it worked out. I always dig into used bikes, you just never know what you're going to find. :)
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Wow, that was pretty cool. Way to be heads up. I'll bet that's a sweet bike.
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got a few hours on the bike now and still can't believe the difference having the valves work right makes.
Now it reminds me of my old piston port OSSA on the bottom. FUN FUN