WLA Misfire

[BAF42WLA]

Hello I am trying to diagnose an issue with my WLA, I recently put my motorcycle back together replacing just about everything mechanical. When I first got it done I had no issues, started first kick. After a few hours of use I started getting a miss in the engine but only when I am in first gear. It happen always under heavy load but sometimes when I open the throttle quickly.(I was thinking low speed was too lean) I have checked all the usual things, points and condenser, I have readjusted my carb 1000 times, new plugs gapped properly, chains tightened properly. It starts first kick and runs great at idle, but when I ride It will jerk and miss until I shift to second gear then it smooths out. The trans was rebuilt by a shop with all NOS parts. And ideas would be great.

[1970 XLCH]

Had a simmilar problem with my VL . I kind of doubt this is it but you never know . My float screw progressively came loose ( over 1000 miles ) eventually droping the float to the bottom of the bowl . This probably not your problem seeing everything is new on your bike . Good luck .

[Peter Cooke]

It happen always under heavy load but sometimes when I open the throttle quickly.

Could it be the coil breaking down under load? My car did it years ago. I never realised there was a problem until I pedalled it down a freeway on ramp one day. Just cruising it was fine.