New top end and no power! HELP

[joshualeeusmc]

Here goes.... I have a 1995 250 Exc, bike was running good, but was loosing the snap. I tore it down and found the head pipe had about a quater inch of carbon built up all the way arround it, the power valve was so plugged with carbon it looked organic, and the piston had some serious signs of blow by. I also took of the flywheel cover to check for any oil and sure enough the seal from the clutch lever was blown. Two weeks and $300 dollars later I had a new weisco pro lite piston, seal for the clutch actuater, and paid the Local KTM shop (the only KTM dealer on Oahu) to clean my powervalve. Now you have the history here is what is going on. The bike feels good down low and has a decent mid range hit, but nothing spectactular compared to what it had before the rebuild. On the high end it has absolutely no power, it falls flat on it's face. The bike will rev all the way up very nice and crisp when it isn't in gear but as soon as there is a load on it power is gone.

What I have checked
-demension "x"
-demension "z"
-power valve operation is good
-tried a wide variety of jetting, and have had the best results with a 50 pilot, 3rd clip on the neddle, and 172 main, Carb is a pwk39.
-repacked siliencer
-Arrow on piston is pointing to the exhaust port
-compression is good

Am I missing something? Please share your thoughts.


-Joshualeeusmc

 

[slodad]

When it is in gear, does the engine not rev as high as before or does it simply take longer to rev and then not pull as hard?

 

[kawaguy]

make sure you got the right size piston, it could be just the slightest undersize for the size of your barrel, but this problem sounds like a powervalve prob, make sure you put it back together properly and that you adjusted the powervalve lever, when adjusting it make sure the pv is fully closed and flush inside your exhaust ports and barrell before your set it right.

 

[JasonJ]

Is the flywheel Keyed? Is it possible the timing is off?

 

[joshualeeusmc]

Is the flywheel Keyed? Is it possible the timing is off?

You are right on, Did some digging arround and found the woodruff key was sheared off, but the timing only moved about a 1/4 of an inch, just enough to kill the bikes power.