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Author: Subject: how does a motorbike starter motor work?
hexxi

posted on 22/6/10 at 07:56 PM Reply With Quote
how does a motorbike starter motor work?

How does a motorbike starter motor work in general? I just opened the left side engine cover of my Rotax V990 (from Aprilia RSV mille), and noticed that the pinion is in permanen contact with the flywheel (ok, there are two gears between).

According to my knowledge, in car engines the pinion of the starter motor moves axially to the flywheel when the engine is started and then returns back. When the engine is running there`s no contact between the starter pinion and the flywheel.

So it seems that the starter motor rotates the whole time with this motorbike engine. Does it make any sence? Or could it be that there`s some sort of clutch inside the starter motor? The motor feels quite heavy when turning the pinion so it`s quite hard to believe.

[Edited on 22/6/10 by hexxi]

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MikeCapon

posted on 22/6/10 at 07:59 PM Reply With Quote
There's a freewheel system, generally hidden in one of the 'idler' gears. That's it really. Simples.
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dinosaurjuice

posted on 22/6/10 at 08:03 PM Reply With Quote
its essentially a one way bearing but above a certain rpm the 'rollers' retract out the way completely so no friction. can be a pain to re-assemble...
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jase380

posted on 22/6/10 at 08:04 PM Reply With Quote
and if you spin your car and end up going backwards dip your clutch or the starter motor will mostly be fooked
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ReMan

posted on 22/6/10 at 08:27 PM Reply With Quote
quote:
Originally posted by jase380
and if you spin your car and end up going backwards dip your clutch or the starter motor will mostly be fooked


Almost certainly

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NigeEss

posted on 22/6/10 at 11:46 PM Reply With Quote
Normally a sprag clutch in the gears.





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hexxi

posted on 23/6/10 at 05:11 AM Reply With Quote
quote:
Originally posted by MikeCapon
There's a freewheel system, generally hidden in one of the 'idler' gears. That's it really. Simples.


Is this "freewheel system" inside the starter motor itself?

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MikeCapon

posted on 23/6/10 at 07:17 AM Reply With Quote
quote:
Originally posted by hexxi
quote:
Originally posted by MikeCapon
There's a freewheel system, generally hidden in one of the 'idler' gears. That's it really. Simples.


Is this "freewheel system" inside the starter motor itself?


Here's a piccy. The 'clutch' is a pack of rollers between two rings. In the drive direction they roll up and lock the clutch. In the other direction they act as a bearing. As the diag shows they are not in the starter itself.

HTH
Mike


sprag clutch
sprag clutch

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