I just fixed the power valve on my boy's 65.
Bike ran sluggish, and when I opened up the PV housing, the lock nut was just laying there in the housing. And when I opened up the head, and went to pull out the power valve blade, sure enough, the shaft came out without the blade 🤦♂️
I got a replacement shaft and threaded it into the stock blade with some locktite, new orings on the PV housing and a new diaphragm.
Put it back together, but now the bike cuts out/hesitates/misses at about mid throttle... Low, runs fine, and wide open screams like never before.. but in the middle it's VERY unpredictable.
Poor guy has an arena cross race on Saturday.. I don't feel comfortable having him race on it 😕
What could it be? Has anyone experienced this before?
Thanks ahead of time!
I chased my tail on our 65. Ended up the stator side crank seal. Pretty easy to replace once you get the flywheel off.
So I disconnected the pressure line from the exhaust and then tried riding it again..
It's most definitely something up with the power valve.. even though it opens and closes when I'm blowing in the tube..
So we're just going to leave it disconnected and zip tie the tube off so it doesn't splurge all over the engine...
With the power valve completely eliminated.. at least he'll be able to race.. he just won't have full power 🤷
I'm going to order a Nihilio blade tonight and hopefully we can swap it out next week
Is the blade moving up and down freely? Not sticking from carbon buildup?
As far as I can tell..
I even did the "blow in the tube" test w/ my boy, and it seems to be working fine... not sure what's goin' on....
You can see the test being done here: https://photos.app.goo.gl/YD7VagKe6YMN39EKA
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Plug, coil, stator, reeds
Check these threads for a few more ideas.
https://www.vitalmx.com/forums/tech-helprace-shop/ktm-65-air-leak
https://www.vitalmx.com/forums/tech-helprace-shop/ktm-65sx-cutting-out-14-full-throttle-electrical-questions
I sprayed carb-cleaner all over the engine and crankcase while idling.. no panic revs at all.
So I''m thinking it's not a leak..
Did you check the left side of the crank for play like those other threads say? Play in the crank could cause the left side seal to leak intermittently or for the ignition pickup to be intermittent.
I think some carb cleaners are inert due to EPA reasons. I use an un-lit propane torch, take the stator cover off and give it wiff by the seal.
Check your pilot jet....hold it up to a light and make sure nothing is blocking any of the very small openings. Ive had some lint find it's way into my fuel and eventually partially blocked my pilot jet and the bike was having the very same symptoms
I'm late to the party but as the author of one of the referenced threads I tried everything, after changing the crank bearings and seals the movement in the crank was gone and so was the problem.
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