150 valve spring and cam recommendations

[dandanman232]

Hey guys I’ve had experience building gokart motors and I know to get the most out of my motor I need the stiffest valve springs and the cam to match lighter flywheel all that. Well I want to get the most out of my gy6 without bbk bc I know this motor has enough power I just want to unleash it all and can’t find any info of how many pounds the valve springs are or the ratios for the cams . Can someone who really knows how to build motors give me some advice or a link to make it easier. Also what gears for the transmission and overdrive pulley?thanks guys . I can’t figure out any difference on the gears but just want the highest top speed I can get out of it so I don’t have to hold it redlined everywhere I go figuring it would last longer that way

[dexameth]

Welcome! GY6 springs aren't rated at pounds, but merely "rpms". I sell "12k" springs that are MUCH lighter than stock and MUCH stiffer... they also allow use of the high-lift cams. Some of these cams, like A10 or A11 will be too high for the stock springs and will bind them. Find the springs here: RDR 12K SPRINGS. You can also pair those with Titanium Valve Retainers to really lighten the load on the valves.

As far as gearing... that depends on the setup. The same gears for a scooter might not be good for the buddy/gokart (power to weight ratio and whatnot). I'd put a lot of effort into the CVT after you tune the head (port it for more flow, and run a 26mm slide carb for real nice flow).

Aftermarket variator increase the CVT's operational range (meaning more to range to play with). There's a LOT of options in that area... then the weight of the rollers inside the variator determine the RPM range (lighter for higher RPMs and heavier for lower RPMs, tune to your desire). The variator / CVT system basically harnesses the power the engine is creating. Stiffer contra springs in the clutch help hold the belt in the "powerband" better, but too stiff can limit speed.

I would definitely upgrade that head and valve train, then work on the CVT tuning and when all that is done, look at gears. Keep in mind the CVT will need to be retuned after a gear swap.