my son has a scrambler 50 just put a 19 tooth front sprocket . how much difference should we see and is there anything else we can do. ? would like to go into the motor and put a 70cc big bore kit pipe any suggestions would be appreciated.

 

WRH Racing has a 70cc kit - and a bunch of other stuff.
Hetrick Racing
Peak Powersports
They have this stuff as well. I had just read an article that used WRH's kit.