[alex3012red]

It started with changing the intake valves, after a baja trip,(would no longer start, intake valve) took head apart changed valves both intakes, and checked clearance on intake/exhaust, i also re-jetted the carb, don't remember off my head but i think its 165 main 48 pilot and crf 450r 05(i think) needle 3rd pos. got it off this forum, re packed mufler, anyway the bike now starts right up, idles good but misses or sputters and back fires on acceleration around mid accelarator, i have checked just about everything i could think off, i even went back tore the carb appart to recheck it put old jets back in, checked grounds, checked timming (like 4 times) cause it sounds like its off time, i also forgot to mention i put new batt, and starter solenoid. sorry for the long post, any ideas on what to check now, just about gave up on the bike, spend 3 days working on it with same results, just frustrated

[JimDirt]

What is the Fuel Screw set at ??? , when you went thru the carb did your replace the O-Ring for the Fuel Screw ??

It sounds like the Fuel Screw issue or a Exhaust leak , either at the mid pipe to muffler connection or at the header to head connection

Those would be the first places i would look , if it starts easily , i would think the timing was OK ....

Could also be the spark plug breaking down , or a loose connection where the Coil power wire is plugged in , sometimes when removing or installing the tank and running the fuel line thru that area , it pulls the connector off the coil pin and it will be barely getting contact , its a real common issue on the X because of the 2 fuel lines at the valve