jetting or timing

[dethwishwayne]

i have a 70cc a/c malossi mhr drr90 pipe and i just put a 24mm pwk on it
once i got it installed and the pilot adjusted i started revving to see how it was running on toppend, wheels are off ground. it runs awesome to about 1/4 throttle and rpms shoot up to about 11300 then it starts slowing down i can't really hear it bog or sputter, wondering what you all think? i started with a 120main and went up to a 125main couldn't tell much difference

[nitrofish]

I would say that you have reached the max rpm potential of that 90 pipe. Jetting sounds lean by the numbers, hows the plug look? Matt.

[Logan #34's Dad]

Jump to a 135ish main and see if that does anything. Then work from there. When things are off -like you discribe- changing just one jet size will not let you know what the problem is.