no power.....

hi,
i`ve got a big problem with my 49cc cag....i doesn't rev high enough!

First of all my mods:
48ccm bb cylinder (exhaust port 1mm higher)
15 mm sha carb with 68 main jet
zocchi intake manifold
pro pipe exhaust pipe
4 reed petal kit
malossi mhr 45° reed assembly for racing scooters doing 20hp + (70cc)
new ngk spark plug
clutch springs stage I

first i tried a 76 main jet but the bike ran only 10 mph....
i switched to a 70 main jet because it ran VERY rich with that 76 --> better result about 9800 u/min on a straight street.
next attempt with a 68 main jet --> 10060 u/min on same street

now i ran out of jets to go more lean.... but isn`t a 66 main a little bit to lean? with all these parts my cag should be able to fly... :-( but it doesn`t...
and accerlation isn`t that impressing as i first expected... (std. ratio)
PLEASE help me and excuse my bad english....
Tim

Are you using a base gasket?
Also check your plug to see if you are still too rich.