...i'm pretty sure that stock rollers are 6 gram..
...i would definately think the 4.3s will bee too light...maybe even too light for a stock 50cc...
..if you have the stock carb, the main jet will probably get you by...there are no needle adjustment notches on my carb, so I modified the nylon holder, and put a washer beneath the needle, raising it .025"...you can probably work out the idle mixture with the screw on the side of your carb...
..if you believe the valves are "tapping", i would stop where you are...you need to verify that they are set right before you go any further...You'ld not want to damage them....