Running Problems

[Bugsy]

Hi Everyone, I own a Joyner 650, and have had running problems since i bought it, seems to be a big flat spot on low rev's, have tried altering the mixture screw every which way but loose, and it does'nt make any difference what so ever, but it seems to run o.k with a little choke. This tells me it's not getting enough fuel !
So i reckon the carb want's re-jetting, i've recently fitted a performance exhaust, can any one tell me the jet sizes, Pilot and Main for smooth running.

 

[Lilspeed]

Hi, and welcome to Muddybuggies!

I'm afraid I know very little about the Joyner specifically, but I do know that on any engine the symptoms you're describing can sometimes point to an air leak on the inlet side of the engine.
First things I would check - Are all breather/vacuum hoses connected and in good condition? And are all carb/manifold bolts tight and gaskets in good order?