honda spree pipe design Please help

[playabarz]

Ok heres the thing yesterday i put a pocket bike expansion chamber on! Heres the thing i can reach MAX RPMS only when i role a 1/4 throttle back!

Heres what im running

Free Flow uni
Tazland001 special big bore ( Recomend this kit )
and a 95 jet

[Wheelman-111]

Greetings:

That sounds symptomatic of lean jetting and/or an air leak somewhere. When you reduce the availability of air feeding the mixture, the ratio optimizes and produces max power somewhere shy of WOT. When you open the throttle all the way, there's too much air for the available fuel.

I suggest you check carefully for air leaks beginning at the head and base gaskets, the reed block and crank seals. You can spritz any flammable fluid - I've used an unlit propane torch - around the area suspected, and listen for sudden RPM change.

If you find none, increase a size on the main jet and see if it's better.