They make a propane touch for melting frozen cattle tanks, the control is a manual lever. It throws flame about 4 ft. With a little plumbing this could be mounted to the exhaust pipe. Using an igniter from a gas grill should give a good flame. I would use a small propane bottle . Be careful.
You might contact Dragon Man in Colorado springs, he is on the web, he does this with a motor cycle, looks pertly cool. He might shed some light on how he does it.
