RE: losi 42cc big block xxl
Honestly, the drivetrain should hold up fairly well. The reason i say that is because there was about a 20 page thread on here about converting t-maxx's to weedeater engines and several guys did it with decent success. The T-Maxx is smaller and harder to get the engine to sit on, and the driveline in the losi is probably 3x as strong so it should hold up reasonably well. Those guys were saying to just let the 2 speed shift VERY early so that the engine didnt get a lot of rpm before it caught 2nd gear that way there wasnt any real shock. Having the truck shift to 2nd as soon as it started moving would probably be ideal really. It should have enough torque to not be a problem.