I have an early to mid 70's yammaha (spck) that has new carb an new reed valves 2cycle...no matter which way I adjust air and fuel mixture screws it will not change the idle...also on top end/high r.p.m.'s it starts "fluttering....any ideas? also this is the old 250y trail bike style motorcross..etc.
2007-12-29 11:48:28 · 4 answers · asked by unmisunderstood 2 in Cars & Transportation ➔ Motorcycles
it has leaking crankshaft seals
2007-12-29 12:03:33 · answer #1 · answered by smokey 7 · 1⤊ 0⤋
I would definately follow the first answer, but that would usually cause very limited engine speed due to the charge being pushed out of the crankcase before it gets to the cylinder... either way, it's worth a look.
Before you tear the engine apart going after crank seals, check for a vacuum leak at the carb base. This would cause ghost throttle (takes forever for rpm to drop to idle, or won't at all) and lean burn (causes erratic high rpm... and a melted engine). Fix it fast, or you'll have to solve a bigger problem. 2-strokes don't last long running lean.
It could also be caused by a leaking exhaust, but that doesn't explain the idle problem.
2007-12-31 18:06:47 · answer #2 · answered by Fabio _ 3 · 0⤊ 0⤋
Worn out cylinder, piston & rings.
Remove the exhaust pipe and look in the exhaust port with a flashlight & mirror.
Any scoring of the piston and cylinder wall, or discoloration below the rings, the top end needs to be rebuilt.
2007-12-29 16:07:35 · answer #3 · answered by guardrailjim 7 · 1⤊ 0⤋
fluttering on high RPM with out load;;;not enough gas
wild guess since you already cleaned your carb
loosen gas tank cover ,,seen it only once,breader plug up
2007-12-30 04:04:43 · answer #4 · answered by Anonymous · 1⤊ 0⤋