Bomber electrics problem

[royhall]

Just checked the resistance on the starter between the live terminal and the case and it's zero on all meter ohms settings. A dead short circuit somewhere, or am I getting it wrong again.

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[Deano400]

I'd have expected open circuit for that Roy so something not right.
Is that with the motor on the bench or is it still on the bike and connected to the wiring?

[royhall]

On the bench.

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[K2-K6]

I didn't think there should be any contact from pos to  case, if that were so that should be a problem.

What have you got if you go from brush to brush, through the winding in other words.

[Bryanj]

There has to be a reading or the starter wont work, electrons have to get in AND out but it should show resistance NOT zero

[royhall]

I did notice that the gaps in the commutator were totally filled with carbon from the brushes. Is that likely to be the problem? Will test the resistance on the windings tomorrow.

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[Bryanj]

It could well be mate, we used to clean out the segments with a ground hacksaw blade but not too deep

If you take your multimeter probes set to ohms and check between adjacent segments all the readings should be the same, idealy you should test with a growler but that needs an old school rebuild shop.field coils will seem black and smelly if gone normally

[AshimotoK0]

Also check the soldering of the armature wires to the copper segments of the armature. Sometimes the soldering looks OK but you will see a thin black burn mark line around the outside of the copper wire, which eventually creates an open-circuit
Normal multimeters will be useless other than checking continuity, as the resistance of the armature coils will probably be in the milli-OHm region. Say for example,  the armature current is 100 Amps that would make the resistance of the coil typically 120 milli-Ohms. The best thing to do is pass a known current through each winding and compare the millivolt drop  across that windings (which should be almost all the same value for each individual winding) . As Bryan said the old school method of testing by an auto-electrical shop. would  be to test  with a 'growler' . Another way is to pass the same current through each winding and get a gauge of the electromagnetism created on the steel laminations associated with that coil by holding a small screwdriver near to it. A headlamp bulb in series with the winding would give a decent current.  After cleaning out the segments with a ground down piece of hacksaw blade, as Bryan suggests, I would wash it in something like isopropanol to remove any debris using an old toothbrush.

So what's this 'Growler' thingy/gizmo that Bryan is talking about? .....well I am not going to explain the facts of life to you    but in the electrical world it's this :

https://en.wikipedia.org/wiki/Growler_(electrical_device)#:~:text=A%20growler%20is%20an%20electrical,a%20source%20of%20alternating%20current.

[taysidedragon]

Well, you learn something every day. 😁

[royhall]

I certainly learn something every day, usually things I knew a while ago and forgot. Thanks for all the info guys, I will rebuild the starter motor at weekend using the stupidly expensive kit from Wemoto. £118 What!!!  Will keep you posted. Bye the way, resistance reading across the brush terminals shows zero ohms.

[royhall]

Any ideas on what's the best grease for a reduction gearbox on the front of a starter motor?

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[K2-K6]

I'm using CV joint type black grease on application like this.

Very high anti size, also virtually impervious to moisture, with possibly the best mix of attributes in something loaded as a small gear train is.

If it was constantly running and higher rpm, then plain  lithium spec like wheel bearings use, would be ideal.

It's that load protection ftom molybdenum disulphide that's really beneficial I feel.

[royhall]

Thanks for that. Confirms what I was thinking, and handy that I already have a tub.