I HAVE A JINLING 250cc WATER COOLED ENGINE. THE PROBLEM IS THAT SINCE I REPLACED THE CRANK I CANNOT GET IT TO IDLE. FINE IF I KEEP THE THROTTLE OPEN JUST A BIT LUMPY BUT AS SOON AS I EASE OF THE THROTTLE IT JUST DIES WITH A PUFF OF SMOKE FROM THE CARB. IM NEW TO QUADS SO ANY HELP IS GREATFULY RECEIVED.
THANKS IN ADVANCE

 

Check you got the valve timing right. Check you got the valve clearances right. Clean the carburettor out. When you move the tank and carb, dirt that sat on the bottom for years gets to floating about and can block jets.

 

Ok thanks.will check valves clearances again.have an in line fuel filter so shouldnt really get any crap in carb but will clean out again.
Thanks again.

 

stupid question but did you adjust the idle screw clockwise to raise the idle? If you can get it to maintain there you need to adjust your idle mixture screw in or out until the idle drops, then give 1/8 turn clockwise to err towards rich. Once that is done re-adjust your idle screw to get a consistent idle.

 

How did you "clean" your carb? Pull the pilot jet (the recessed one) and verify it's not plugged.

 

HAVE NOW GOT IT TICKING OVER BUT CUTS OUT WHEN REVVING. IT SEEMS TO BE RUNNING TOO RICH. HAVE TRIED ADJUSTING MIXTURE SCREW BUT DOESNT SEEM TO MAKE ANY DIFFERENCE. HOW DO YOU ADJUST THE TIMING AS I HAVE BEEN TOLD IT MAY BE THAT.

 

Give us a description of "revving". Tell us what happens at idle, at 1/4 throttle, at half throttle, and at full throttle.

 

When giving it some gas it seems to struggle to increas the revs then it cuts out unless I ease off the throttle then it idles fine again. I cant get it to 1/4 throttle without it dying and cutting out.

 

In my experience the timing is not adjustable on these quads. I would check valve lash first. Are you sure you don't get any rev change from adjusting the idle mixture screw? Do you have any intake or exhaust modifications?

 

No mods to intake. It is now ticking over and reving up but when riding it has eratic revs,revs go up and down when holding throttle still. Would having too much lash on intake valve cause this as gap on intake valve is quite big.