Slow Carbide 150

[bugvan]

I have a carbide 150 that is (and always was) SLOW. No low end power at all. I read somebody had one that could do about 40mph with no mods...? I can barely hit 30 downhill. Anybody know what may be wrong?:

[lococanuck]

What type of terrain do you drive in. Sand or hardpacked?
My son just bought one. 40mph on pavement. 30mph max in packed sand.
We installed a 2000 rpm secondary spring and 2000rpm primary springs. Also installed 13g rollers in the variator. We tried 12g rollers but they seemed to light.
We will go out to the sand next weekend and try it out.