kontronik jazz 10-32-55/ twist-42 combo

[RC-Monster Mike]

What batteries are you using? If it starts to act up after 3 or 4 hard launches, it could also be voltage drop (I am not too familiar with the kontronic stuff, but most controllers cut out when the voltage drops below a % of the starting voltage), although 10 cells shouldn't drop voltage that quickly. Drop a couple teeth on the pinion and see what happens. Ultimately, you would probably be better off with a better matched set, though(smaller motor or bigger controller).