OzVMX Forum

Clubroom => Tech Talk => Topic started by: PCMAX on July 05, 2014, 01:24:29 pm

Title: Engine "Running On"
Post by: PCMAX on July 05, 2014, 01:24:29 pm

I have a CR125 that tends to run on a bit when I shut off the throttle. I've checked for leaks from the inlet boot, gaskets etc all OK there and the idle is good when stationary but out on the track it never seems to run back to idle when I close the throttle (even with the clutch in).
Could this be a sign of a worn needle jet/needle?

Title: Re: Engine "Running On"
Post by: mainline on July 05, 2014, 01:46:35 pm

Assuming the throttle is actually snapping shut? Ie. The tube spins freely, cable isnt kinked or gummed up. Pilot/airscrew could be too lean

Title: Re: Engine "Running On"
Post by: Canam370 on July 05, 2014, 02:00:35 pm

Sucking air somewhere.

Title: Re: Engine "Running On"
Post by: Rookie#1 on July 05, 2014, 02:30:17 pm

How long since you've replaced crank seals?? :-\

Title: Re: Engine "Running On"
Post by: PCMAX on July 05, 2014, 02:36:48 pm

Crank seals were new about 12 hrs of riding ago. the slide slams shut when the bikes stationary. The air screw is 1-1/2 turns out. Might try another carby.

Title: Re: Engine "Running On"
Post by: sleepy on July 05, 2014, 03:31:51 pm

Turn the air screw almost all the way in and try it. Also make sure you don't have any leaks around the top of the carb. Seen one just recently that was mising the gasket from the top of the carb and boy did it run on.

Title: Re: Engine "Running On"
Post by: vmxrider on July 05, 2014, 05:06:32 pm

A leak down tester might will help with diagnosis,
http://forum.ozvmx.com/index.php?topic=24254.msg237606#msg237606

Title: Re: Engine "Running On"
Post by: evo550 on July 06, 2014, 09:23:50 pm

Have you fitted an aftermarket pipe?
Changes in Weather/temp can really effect jetting.

Title: Re: Engine "Running On"
Post by: Lozza on July 06, 2014, 09:35:52 pm

Pilot jet too small and/or slide cut away too big.......maybe the air leak