Posts
47
Joined
1/19/2024
Location
Chicago, IL
US
Hello Vital, My friend has recently bought a 1991 kx125 in decently good condition, starts easy, runs through all the gears. the only issue is, it’s slow as a dog. The bike gets beat in acceleration by my PW80 and my other friends TTR-125 easily. It’s not even a close race. The bike revs out good, has stock jetting, and from what I know a good top end, new spark plug, fresh fuel, and good spark, so what could be causing this bike to be so slow? Thank you in advance.
Clutch could be slipping.
Could it be due to incorrect assembly / poor function of the exhaust power valve?
We just replaced it 2 weeks ago. Was my first guess. However it turned out it’s still horribly slow.
We haven’t been into the top end yet. The power valves seem to function and open normally? Is it possible they would function normally if they were incorrectly assembled?
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If the gears are misaligned, the valve will not open completely, with a consequent loss of engine performance.
I don't Know if this is your problem, but you can remove the exhaust pipe, and release the valve linkage to move them manually and look through the exhaust outlet.
Check also this video:
https://youtu.be/ZY_hI4LocO8?feature=shared
Cheers.
Check the exhaust pipe and muffler for blockage.
Thank you. I’ll do that when he brings his bike to my house so we can change tires.
We’ve had the exhaust off to weld it after he busted a hole through it. (Fell perfectly on a rock) and repacked the muffler while we did it. I don’t believe there is a restriction. Thank you for the ideas though.
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