I researched this after seeing them in action several times, the washing my cylinders down on my motor convinced me to forget it, not worth the chance of shorting the engines life. At our local cruise night we have a guy come in with propane flame throwers, was pretty neat until you really realize its the same thing as taking the ol' brush burner out and squeezin' the trigger, nothing is coming from the motor, it just looks like it, I guess the exhaust velocity throws it a little further maybe, was neat at night, heck he could actually do it with the motor off even...