Looking for input on my '07 S40.  Its completely stock inside and out.  I've just recently gone through about everything to get the bike to run.  (bought as a non running project).  The carb is clean, raptor petcock, new spark plug.  

Anyhow, I recently adjusted the idle screw about 3/4 turns richer, hoping to get rid of the back fire while slowing down.  This did indeed fix the problem, as I now get a small burble at the most.  

The issue I have now is at lower RPMs, the bike feels like its surging or hunting.  If I select half choke, the bike runs its best.  It instantly runs smoother, sounds better, and rpms raise a bit.  This is well after the bike is warm.

With this happening, would a larger pilot jet fix the issue?  Above 1/2 throttle it seems fine.  What exactly is half choke doing, as this is what it seems to like most while under 1/2 throttle.

Thanks

Serowbot wrote on 08/15/14 at 16:42:24:



I'll give it a try, thanks.

I used to notice the surging before I changed my pilot jet and now that I have the correct size one in its much worse. Next for me is the spacer mod. I am not convinced jetting would help this. When I am done with the spacer mod I will let you know how it rides.