I recently replaced the valves, springs, etc. along with a new top end (Wiseco 13:1 high compression piston) on my 2005 CRF450R. I initially put .6 hours on it during break in and then changed the oil and parked it for the winter. It was 50 degrees today here in Connecticut so I went riding. At about the 1.9 hour mark (per the hour meter) while riding today at a local MX track, the bike started to sound noticably different (lots of popping on decel) and began to run very rough. It was fine all day and ran smooth, no popping on decel, no overheating, nothing. After making it through a rhythm section of jumps, I pulled off and headed back to the trailer (I was spent and could barely hold on anymore anyways!). When I got the bike home, I checked the plug and it was very white (indicating a lean condition). I also checked the air cleaner and boot and both were spotless.
When I broke the bike in one day in November, I set the fuel screw to 2.25 turns out (that is where it ran the smoothest with the idle up high). Since it was slightly colder today, I backed it out another .25 making the screw set at 2.5 turns out. Other than the high compression piston, I also have a White Brothers Carbon Pro exhaust system. The jetting is stock. Any ideas what might have happened and what I should do to diagnose?
When I broke the bike in one day in November, I set the fuel screw to 2.25 turns out (that is where it ran the smoothest with the idle up high). Since it was slightly colder today, I backed it out another .25 making the screw set at 2.5 turns out. Other than the high compression piston, I also have a White Brothers Carbon Pro exhaust system. The jetting is stock. Any ideas what might have happened and what I should do to diagnose?