Surging/Jerking at half throttle

Jonathan Zarnoth /

Recently kitted my A3 with the Treats Tomos A3 party and an Endy pipe. Also using a ZA50 CDI, stator and flywheel. Everything works great at idle, accel, all the way through WOT. The surging/jerking starts when coming down from WOT to about part throttle just trying to cruise along at normal speeds. Once stopped idle is normal and accel is normal...which kind of leads me away from an issue with the cylinder itself and to either a carb tuning or transmission issue. haven't done much to troubleshoot yet just wanted to see if anyone had experienced the same symptoms to give me a jump off point. Thanks!

Re: Surging/Jerking at half throttle

Jonathan Zarnoth /

oh yeah, running a 69 main jet. plug looks good and chocolatey.

Re: Surging/Jerking at half throttle

I'm having a similar issue when i cruise at about 30mph at about half throttle. I will just be plugging along and i will like jerk a tiny bit under me then start to accelerate. (i'm not an idiot, i'm not on a hill.) I have no answers, but you are not alone.

Re: Surging/Jerking at half throttle

jerking off at half throttle?

Re: Surging/Jerking at half throttle

Overpriced Parts /

Tune your midrange people

Re: Surging/Jerking at half throttle

sounds like lean serge. try a slightly richer mixture in the mid-range carb circuit / needle, jet? not sure what carb your running

Re: Surging/Jerking at half throttle

Fuel starvation? Gas cap not venting? Petcock too restrictive?

Re: Surging/Jerking at half throttle

WOT works all day??

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