I OWN A 99 TRAILBLAZER THE MOTOR IS 60 OVER HPD PIPE AND CLUTCH KIT
STOCK CARB IT PINGS AT 3/4 TO WIDE OPEN THROTTLE I HAVE A 165 MAIN JET. IT DOES IT AFTER I RIDE IT AT THIS SPEED FOR 50 TO 100 YARDS IM WONDERING IF THE CARB IS TO SMALL OF IF I NEED TO GO BIGGER ON THE JET PLEASE HELP THIS WEEKEND I PUT THE 165 JET IN AND IT STARTED TOPING AND LOSE POWER I BACKEDOFF THE THROTTLE IT STOP AND I GOT BACK ON THE THROTTLE AND IT PINGED JUS A SLIGHT BIT.[img]i/expressions/face-icon-small-disgusted.gif[/img]

 

Pull the sparkplug, If it's not a dark tan or brown, you're too lean and will burn the piston.
Also, since the bore is .060" over, I assume that you have a wiseco piston. ALWAYS LET THE ENGINE WARM UP BEFORE YOU RIDE HARD !!!!

 

You need to run premium grade pump gas as well. My Xplorer pings sometimes if I use 87 octane, so I changed to 92 minimum. Haven't had a problem with pinging since. Running lean can cause the same problem. Check into what CaptNemo suggested before changing over to premium.

Waylan