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
The magneto (generator) for the bike is comparatively stronger than in a car. So all you need is a circuit path (ie, key turned in ignition), and turn the engine over quick enough. The magneto turns when the engine does, so if the engine is turning fast enough ***for any reason*** you’ll have power getting to the spark plugs. So turn the engine with the key on, the engine just fires right up. Done it many, many times with my bikes.
Use 4th gear so that the least movement of the rear wheel results in the most revolutions of the engine. If the tire skids instead of turning when in top gear, lower the gear setting. The tire will more strongly resist turning in higher gears, so lowering it will make the wheel turn easier. You may have to push the bike further, but a lower gear will usually work, too.
(biker long ago, tech may have changed)
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