Linkage Adjustment

[MaxOut]

Originally Posted by StoveBolt

Try adjusting it as long as you can and still be able to hook it back up and sometimes back firing is caused by the throttle plate not closing all the way when you let up.

Agreed, adjust the linkage and check throttle butterfly to make sure it completely closes when pedal is released. Make sure you check it after full throttle when testing to put stress on linkage. The problem could also be a sticky butterfly valve in the carb as well. The surging comes from the linkage adjusted or butterfy at partial throttle before ignition is reached. Back it off and your issues should be gone.