it's been so long sense iv dealt with this i don't remember what's causing it. i want to say clutch. i know the clutch bell spins freely when the motors off so the shoes aren't dragging (4 shoe clutch). it takes off/drives when just idling, and at a good pace. i have to hold the brake to keep it from driving off and even at full brake it still inches forwards. the idle RPM doesn't change (lower) when on the brake. so I'm pretty sure the linkages and carb are adjusted correctly. anyone got $ .02?