running rough after rebuild

[2fittyr]

I just rebuilt my top and bottom end, went to the 87 rod and piston, ported and pollished, jetted to 164 and put a fmf on, it runs real good until about 3/4 throttle then just starts sputtering.

I was thinking rejetting but this is all new to me, some advice would be appreciated

[Dave83]

Providing you have broke it in decent,jetting or needle position is probaly your problem.What altitude are you at?If its been heat cycled a few times,take it up to wide open and kill it with the throttle open(try getting to 5th 0r 6th gear),take the plug out and see what it looks like.Wet and black=jetted to fat.You will be looking for a tan(papersack) color when its right.