The last two responses from Cab and 4 gear are spot on twocents
Your surging is likely the motor telling you it has too much advance whistling

Also, checking for pinging due to excess advance is best done from low RPM and speeds (20 MPH or so) in 3rd or 4th gear while putting the motor under a heavy load like climbing a hill, and then accelerating from both part throttle and again at WOT wink

Last edited by TJP; 10/04/21 10:00 AM.