Originally Posted by hermet

I am just starting to get into racing at my local club (only raced once) and have to run 21.5 motor and blinking speedy. I am building a 6.1 kit at the moment but have been told the kit gear ratio is wrong for 21.5 What would be the correct pinion and spur sizes?
I have tried to put a 64 T spur and a 36 t pinion but I now i can't get to the motor mount screw as the spur covers the mounting screw hole on the motor.
Anyone had this problem before? I can't find much on this issue.

Thanks