Found a forged rod for 142F/144F

[Old Busted Hotness]

The stock cam is plastic, only one lobe operates both intake & exhaust. There's room to reduce the base circle, but you're going to run into issues with the followers if you take too much off. Also the valve springs only have so much travel.

 

[Will'smotobikes19]

Stock springs are 11 lb right? or is is 10lbs. I wonder if you could get some 0.93 13lb springs,

 

[Chainlube]

If you look into go cart sites you might be able to find stiffer ones. Look at junior carts, they might have them for those.
Sorry forget that, you're looking for a 50 cc.