"Why are his hands on fire?"
I'll not forget those famous words from my friend and partner, Ted Dale, when a mechanic at our service and repair shop in Loveland, Colorado, ran by.
The story starts when the mechanic had seen us starting old barn-rescue bikes by spraying WD40 into the inlets to see if the bikes would run. Almost weekly we would have a request from a customer to "check out this old bike to see if it's worth fixing up."
After going over bikes to make sure the engine didn't have internal damage, and that there was both oil pressure and circulation, we would spray a little WD just to check if the bike ran.
Without exception, all bikes that have stood for some time with gas in them will need a carb rebuild/clean, but by spraying some WD40 into the inlets, we could bypass the fuel supply.
Engines would generally start up, which indicated the bike was worth "fixing up."
However, if the bike didn't show any signs of starting, we would not spray any more WD40. The aforementioned mechanic--the one with hands on fire--thought if a little spraying was good, a lot would be better! His bike back-fired through the carbs and ignited the air box, the can, and of course his hand.
Luckily, he had gloves on.