Oo man, that fire-button has kept me out of my sleep. I pushed every button the keyboard and I came to the conclusion it has no function.
BTW, my pressing all those buttons I found a cheat in motorcycle counterpart of this game (Grand Prix Cycles). Press M, or Alt-M, to remove the map during qualify and when the race starts, all your opponent are frozen. Just be sure to qualify amongst the top-4, otherwise you'll crash into the bike in front of you. If you're racing a multi-lap race, press M, or ALT-M, to get those opponents racing again.
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EVERYBODY DANCE!
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