565
Scoot Junior
Posts: 12
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Post by 565 on Jun 13, 2023 4:39:30 GMT -5
hi i have gy6 139qmb. It has a big bore kit 47mm, motoforce crankshaft, top racing variator, bigger Majn jet, I also tried different clutch springs and torque spring, the engine does not go more than 60 km/h. The compression is good, the valves are aligned and so is the ignition. With the standard 50cc piston, the engine ran 70km/h. someone help me.
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Post by aeroxbud on Jun 13, 2023 5:26:09 GMT -5
Has it got a restricted CDI? What does it rev to?
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565
Scoot Junior
Posts: 12
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Post by 565 on Jun 13, 2023 6:24:29 GMT -5
Has it got a restricted CDI? What does it rev to? it revs 8500-9000 rpm it has standard cdi |
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Post by GrumpyUnk on Jun 16, 2023 10:15:41 GMT -5
The high revs are sitting on the center stand, I presume... which provides very little engine load, so is easy to achieve without a lot of throttle. I would check that the throttle opens fully, the slide moves up and down freely, the diaphragm is not damaged, and the engine will open the slide without problem. I'd also check that there is not leakage in the intake system such as a wrinkled gasket, crack in the elbow, loose nuts, etc.
If you had more performance prior to the new piston/rings/cylinder, then either you don't have the power of the 39mm, or something else has changed. You do get full fuel line diameter flow from the tank if you apply vacuum to the petcock, right? There should be no dribbling, but a full size flow through the tank outlet screen, the petcock, fuel line, filter, and final line. Restriction in any would cut power.
Assuming the intake filter and housing are not blocked, and the down pipe and muffler have not been invaded by mud daubers(had that, hard to figure out) clogging your exhaust, and all the parts are correctly installed and the cam timed properly, things should be better than reported.
tom
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