where do I start?

hcrft · Jun 13, 2014

I have an engine on one of my bikes that from the start never seemed to want to return to idle once moving. It had a whiny gear sound and a horrible vibration that developed over time. The engine is new with only a dozen or so rides on it.
the vibration is worse now, and the engine revs to a certain rpm and will rev no higher. If you hold the throttle in fixed position the engine revs up and slows down repeatedly.
Ive tried different carbs and the problem persists.
Gonna open the engine and have a looksee.
Where should I start?
what might I be looking for?

Greg58 · Jun 13, 2014

Whining gears sounds like the gears are dry, remove the right side cover and check for wear. If the gears look good apply good grease to a couple of spots on the gears, not a lot or your clutch may slip. With this cover off check for fuel residue near the small gear, a leak here indicates a blown seal. On the left side you also have a seal behind the magnet, look for fuel in that area also. Vacume or in this case pressure leaks will cause this.

hcrft · Jun 13, 2014

Thank you for the advice. In retrospect I think I was also unkind to the engine during break in. Not enough oil in the gas for a break in, and probably went too fast too soon. The bike I finished thursday is running 20:1, no more than 30min at a time, and no more than 15mph til 50 miles.
I have a spare cylinder and piston. Gonna remove the head and look for premature wear.

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where do I start?

hcrft

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Greg58

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hcrft

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