Problems with my JPX .28
 

i've been having a problem with my jammin motor for a week or so now. whenever i go full throttle and let off it keeps revving. before you say the bottom end is too lean, it isn't i've richened it up to the point where i can barely rev it up and it will still do it. i've richened the high speed needle up too. the carb does not stick i've taken it apart and polished the barrel in and out i've checked my linkage a million times i sealed the carb and even sealed the hs needle. any other suggestions?

If nothing is working then try re-setting the engine to the factory settings and re-tune the top end first and then the bottom end.

If that still doesn't work then you've probably got an air leak somewhere.

check your servo, maybe try another one, if your endpoints are set too far and your servo is opening your carb all the way and straining to go further, you might of stripped a gear or fried something in the board.
A lean top end will do that as well sometimes.

ive reset the carb numerous times... my servos endpoints are fine too the carb opens and closes fine... i though about an air leak too how do you check that your front bearing is or isnt leaking?

what about your clutch?? if it is worn down on the edges it may be sticking to the clutch bell

hmmm never thought of that ill check it out thanks!
\

Does this only happen when you hold full throttle for more than a few seconds?

How high does it keep revving once you return to idle after giving it full throttle?

Does the revving eventually stop and the engine return to a normal idle?

Did you try pinching the fuel line after a few seconds of it idling? The engine will eventually cut out, but does the rpm go up or down before it cuts out?

yes it is usually at or near full throttle when it happens.

when i hit the brakes the engine stops revving eventually other then that it does die down on its own but takes a while... i usually hit the brakes so that it doesn't stay reving for so long.

i've done the pinch test at different carb settings and i've had all results including the supposed proper one where it revs up minimally then shuts down. but it will still keep revving after i hit the throttle.

i just took the clutch apart and there was some minor shrooming but i grinded it off then sanded the inside of the clutch bell put it back together and im still getting the same problem... i have an 8t and the clutch has 4 aluminum shoes with all silver springs... i bought it used like that and it worked for a while untill this last week.

thanks for the help everyone.

Maybe the issue is that your idle speed needle is set incorrectly. This is the one that controls the idle speed.

i've set that to the point where it barely stays idling and it still did it lol, ive had no luck with this problem.