A friend of mine is a mechanic, and long ago he told me if my motorcycle’s battery fails and I can’t get another vehicle to help me with jumper cables, what I have to do is have the ignition ready, get it into 4th gear, and after giving it some momentum to suddenly release the clutch.
How does this work, and why 4th gear specifically?
In: Engineering
It sounds like your friend is describing a push start, or at least that’s what I’ve heard it called when talking about cars, bikers might have some different lingo.
But what’s happening is that by getting the bike, or vehicle, rolling with the clutch popped, you build up some momentum, when you engage the clutch part of that momentum is suddenly going to be resisted by the shaft and the engine, rotating and moving the parts.
Since the engine is already starting to spin this lowers the amount of energy necessary to get it to turn over and start, meaning you don’t need the battery to work perfectly to do it.
Though be warned if the battery is truly completely dead, this won’t work, it stills needs to be able to spark the engine to life.
As for why is has to be in 4th gear, I’m not sure since in cars you typically do it in second gear, but my guess is that putting it in higher gears means there’s more resistance to spinning, so you don’t get the engine and parts spinning too fast to start. Though that might be different with a bike.
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