I am currently building a custom large scale monster truck. So far I have a basic frame(30" long wheel base) and an engine. I plan on setting it up for a chain drive 4x4. What I am not sure about is the tire size I want to use. I have found some tires off of a roto tiller, the ones that look like monster truck tires , they are 13 inch out diameter and 5 inches wide, I have aluminium Go Kart rims to mount them on. The question I have is... do you think that a 30cc chainsaw motor could handle them? I am also just using the stock centrifugle clutch. I have heard of people using a 30cc to power gas scooters and bicycles, and I figure if it could pull 100+ lbs @ 20-30mph, that it can drive a 40 or less lb truck at that speed. If all else fails I can chop the frame and lessen the scale. Any advice would be very helpful... especialy for steering those big tires .