Characteristics of a Primary Gear up kit

right,
i bought a set of cases from nrg andy, they had a malossi mhr crankshaft and a malossi primary gear up

i then build my engine as normal fitted my polini sport to it etc but im finding it realy weak. with the exact same setup my topspeed was lower by about 4mph (give or take) and now im running my airbox again its dropped even lower to about 60 clock speed

now it sets off ok and flatout is about 9500rpm, but im only seeing 60-62 at the very most, my standard 50 indicated that speed

So in a nutshell, my 70 has become slower than my 50....

any opinions advice?

thanks


My current setup:
Polini Variator
7gram rollers
doppler s3r
polini sport
malossi crank
malossi primary gear up
standard carb and air box (102 main jet)





oh one more thing, anyone have a clue why my main jets are always massive? was running a 142 jet with an open air filter, now on a 102 with bigger airbox. theres no air leaks etc

cheers

 

Overgeared maybe... gearings too high for the engine to pull when flat out and hence its lost some speed?