Wats best gearing??

http://www.blasterforum.com/general-support-17/i-made-blaster-specific-gearing-calculator-40628/

Here is the gearing calculator Luni made.

According to the calculator you'd be able to get up to about 57.7 mph with 20 inch tires. That is assuming you weigh absolutely nothing and you're ridin in a vacuum.

High front, Low rear = Speed
Low front, High rear = Acceleration

But remember, you can't have both. Find what you want, it will depend on your style of riding. If you ride MX or trails a lot you'll probably want more acceleration. If you have a lot of flat straights you might prefer a gearing that'll get you more speed. There is no one best gearing.
 
With taller, high speed (15-36) gearing you have to have power to "pull" it. A stock blaster might not be able to get out of 4th gear and accelerate like a snail. :o Low gearing (12-44) will accelerate like John Force, and top out at about 55mph. Can't really have best of both worlds. X(

You have to decide do I want more speed or do I want to get to speed quicker? Best way for more speed is to start modifying your engine. I:I