How about this ratio?

[JourneyMan]

How good would a 12 tooth front sprocket and a 52 tooth rear sprocket be on a Yamaha blaster. I am looking to get some torque and still go over 40mph. About how fast would that sprocket set up make it go? How fast does a stock blaster go?

[2strokepwer]

you will definitely have plenty of lowend power but thats it.can you get a rear sprocket that big? i don't think you can but i may be wrong. as far as how fast on topend i'm not sure.

[TimSr]

Ive got a 46 on the back of my R, and I had to take the skid plate off. you get a sprocte much bigger than that, and youll have to mount a tire on it! Why not just drop to an 11 on the front, which will give you the same as 3-4 teeth on the back.

[JourneyMan]

http://www.bluetraxx.com/gearratio_calc. It calculates speed differences with different sprocket ratios. And yes there is a 52 tooth rear sprocket for the blaster. It is in Denniskirk.com