I am at wits end with this problem. Here are the vitals
Bike- 04 CRF 450 R
Conditions- Altitude from 4300ft Salt Lake City to the mountains at 7500ft, humidity around 37%, temps around 80-100 degrees, trail riding.
Modifications- Thunder Alley full exhaust with quiet core insert.
Current Jetting- 165, 42, and the clip is dead center.
Running Issue- Whenever I ride in the mountains, give a burst of throttle, then pull the clutch in, it almost stalls or does stall. If I wait for about 5 seconds the idle comes back up. I've been told I am way too rich. I think it started around the time I put the exhaust on and I have never touched the jetting. Playing with the fuel screw does nothing to solve the issue.
Problem variances- The issue seems to go away when I come down from the mountain to an altitude of around 4400ft. In fact, I usually have to crank the idle up while I am up the mountain, and by the time I am back down the idle is really high. The quiet core insert made the problem worse when I installed it.
Thanks for your help!