I have either had this happen to me or witnessed it twice in my many years in the industry. On the most recent occasion I was working in an indpendent shop near Phoenix, Arizona. The five of us techs were all crammed together in a 12 x 12 metal shed. Man, that shop was hot! And dirty, dimly lighted, and run by folks who didn't believe in stocking parts, which is another story for another time. Cheek to jowl, we were. Fronting a salvage yard, I apprenticed at making the wrong parts do. It was good experience, in a perverse, reverse-psychology sort of way. And as you would expect, the techs there were not exactly cream of the crop. That is, not the most highly skilled. One day the tech next to me, working on a Gold Wing, started yelling. I turned around to see flames shooting out of his project all the way to the shop's mezzanine, which was built of bare wood 2x4s. Well, one thing they teach you in mechanics school is not to take the spark plugs out of an engine you're checking spark on, but to use spare plugs. I'm sure you know why. With the plug laying on the cylinder head next to the open plug hole and the engine cranking over, you have all the ingredients for having your own flame-thrower. And since it was a Gold Wing the configuration of the spark plug holes was ideal, being out in the open and angled like a rocket launcher, for shooting onto the mezzanine of the shop, on which were stored some restored motorcycles. And I do mean shoot! Like something we would have thought up when we were kids finding stupid things to do in the street. Made for an excitng time, I can tell you!