half throttle sputter

[markvette]

ok we got the motor back togother. got rid of the sparks 440 and went to a 416 with a wiseco 11 to 1 piston. broke the thing in and checked the compression, to my suprise it was 210. i did not think it would be that high with the 11 to 1 piston. i guess we still have to run race gas. now for the problem. my son says it feels stronger than the 440. he pulled the holeshot both motos last night against a 310 r, a banshee, 2 440 ex's and a yfz 450. it runs awesome at full throttle but has a sputter at half throttle. do you think i need to change the pilot jet. it has a fcr 39mm carb with a 155 main but not sure what the pilot is. it did not do this with the 440 in it.

Mark

[terko440]

You will more than likely need to play with the needle clip position. Sounds like you may be a little on the rich side so you would want to raise the clip by a position on the needle. This is very easy to do on the FCR CARB. Good luck.

[Colby@C&DRacing]

The fuel screw needs to be 2 to 2.5 turns out. The air jet needs to be 2 turns out. You should be running a 52 pilot. drop the needle one clip if that does not fix it change the needle to an EMP needle.:)