Re: Scrambler 50 tuning help please!
Mastertech1 is right-on only I'd look for a light tan color on the base ring. Regardless, it sounds like you're running too lean so follow Mastertech1's advice and try a 110. Richer is better than leaner since leaner can melt pistons and / or head gaskets.
If you want more acceleration, install lighter variator rollers. Start with 5.4g weights. Some folks do well mixing 3-4.2's and 3-5.4's (there are 6 rollers total so be sure to install them in alternating order). Going to the 19t front sprocket was a good idea. Next, consider going to a smaller rear such as a 31. Some run as small as a 28, but usually with an 18 front. Don't go too small because the bike doesn't have the power to drive a smaller sprocket especially on hilly terrain such as a motocross track.
If you want more snap off the line or out of the corners, install stronger springs in the clutch. Spring tension controls the rpm at which the clutch engages, or the "stall speed". Setting the stall speed higher moves the running rpm more within the torque curve. Best results are obtained when changing both the rollers and springs. No need to change the big spring (torque driver spring) unless you add a pipe or do cylinder / head mods.
Performing these mods will really wake up a stock bike.