Author Topic: Starter Motor Conundrum  (Read 225 times)

Offline SeanFD

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Starter Motor Conundrum
« on: February 10, 2021, 12:04:11 PM »
Having failed, for now to get my bike (CB450K1) running, - it's a long story involving potentially bent valves and potentially loose cam chain ... – I was looking to see what I could sort out in the meantime. My starter motor hadn't worked from the day I acquired the bike so I decided to try to sort it out.

I stripped it, cleaned it, and checked it out for resistances, shorts etc. Everything, including the bearings and bushes, seemed OK. For some reason, this time - I've rebuilt a couple before – I struggled a bit putting it back together when trying to align the casing marks and get the planetary gears in the right position, but eventually I succeeded.

The motor turned freely, so I thought I was done. Wrong!

I attached it to an old car battery and it turned, but slowly. Even thought the battery was registering 12.8V, it though maybe it just wasn't strong enough, so I next attached it to my Landrover battery. If it can start my Landy, I thought, it should turn this over easily.

Well, again it turned, but still not anywhere near the speed I expected. I tried again and this time it didn't turn at all.

Any thoughts on what could be the cause of this strange behaviour?
CB750 K2 - Ridden from Belfast(SA)-2-Belfast(NI)!
CB750 K1 - The less, said the better!
CB450 K1 - A work in progress.
CB400F Supersport - It's rusty - not any more!

Online Macabethiele (Ted)

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Re: Starter Motor Conundrum
« Reply #1 on: February 10, 2021, 05:40:16 PM »
When I have had this type of issue on cars it's been the windings in the rotor or their connections.
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Online AshimotoK0

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Re: Starter Motor Conundrum
« Reply #2 on: February 10, 2021, 07:17:57 PM »
I agree with Ted, the most likely cause is the armature and probably the commutator or the soldering of  the armature wires to the copper segments of the commutator (if its soldered... sometimes they are crimped). Check the commutator against this from the 450
5-speed Service Manual. There used to be an armature  tester called a 'growler' smutty comments please  ;D ... which auto-electrician's used to use for testing armature windings for shorts etc.

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« Last Edit: February 10, 2021, 07:31:14 PM by AshimotoK0 »
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Offline Tomb

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Re: Starter Motor Conundrum
« Reply #3 on: February 11, 2021, 07:01:54 PM »
I had this on an old Ford Escort years ago, I thought the battery was on its way out, so bought new but got the same slow starter motor, turned out the brushes were worn, they looked like they still had loads of life left in them just worn, they were shorter meaning the springs weren't pushing the brushes onto the commutator hard enough. I bent the springs a bit to make them exert more pressure and the motor went like mad again.

'73 CB550 with CB500 engine café racer
'62 CB77 Sprinter
'70 CD175
'78 CB550 with sidecar
'80 Z50R
And a load of old Yamaha 1100's


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