Most likely a wrong kind of oil; lubrication oils are usually of the mineral variety, and their oxidation is inhibited in addition with additives - partially oxidized oils form gums that clog stuff. Such gums can sometimes be encountered on the shafts of seized cooling fans of ancient computers.
What kind of bike? If motor one, could it be the electrical system? Vehicles rarely spontaneously ignite for other reason.
Yeah, motorbike. It was most likely the electrics; though his mechanic seems to disagree.
Given the partial responsibility the mechanic may admit if heâd confirm the electricity hypothesis, if he worked on the bike before, no surprise.
I think westcarleton doesnât understand that holding a laserpointer steady enough from that distance would require it be mounted on a tripod. Add to that the attenuation and diffusement caused by going through a tinted window, and the odds of it being a laser drop to pretty much nil.
I made some pretty good dark-time photos by improvising a tripod by holding the camera against a fixed object. Pressing the laser body against the window frame so it wonât move, or even holding it in a fist laid against the window, would work for steadying it well. We do not know if the glass was tinted, and if it was, if it absorbed enough at the laser wavelength to be of concern. The reflection on the glass-air interface is more of a concern here.
That said, I am by far not certain it was a laser.
Too bad none of my short-wavelength ones are strong enough for a test, and the CO2 one wonât go through glass and I wonât be taking it out of the cutter because the alignment takes work. So no experiment to mythbust the hypothesis. 
i guess (ahem) it was a baking tray. Partly burned pizza anyone?
Even if you could hold it in place long enough in one spot to start a fire, thereâs no way youâre going to create a square burn. And remember, it only a square when looked at from above, Youâve also have to compensate for the angle.
Once you ignite it at a single spot, the fire will grow either conventionally round, or, if the substrate anisotropy is sufficient, square. Remember we have orthogonal woven fibers, and the fire may find it easier to propagate either along the fibers or in 45-degree angle, which both results in a square.
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