Starter armature damage

Hey guys,

Last year I picked up a junky 1983 kz440 for almost free. I managed to get it running that day but the starter promptly crapped out on me. Just wanted to get your opinions on how to fix it/what to do. As a disclaimer i just bought this bike to tinker with and I have almost no mechanical experience, so go easy on me

When i took the starter apart i noticed some damage on the commutator

I rebuilt it a few times trying different things to make it work. I noticed that each time i bench tested it, it would run good for about 5 seconds before slowing down and inevitably coming to a stop. Each time i took it apart afterwards, there would be black material on the rough part of the commutator. It would also always stop in the same position, with the rough part just beginning to touch a brush. So i had the commutator machined...

the guy said he couldn't take any more off because there wasn't any material left, as you can see there is still a bit of a rough spot. I put it in and had the exact same problems as before. I thought the black deposits were from arcing but my friend suggested that the brush material had gone soft due to its age and should be replaced. I purchased the starter kit and installed it, which changed nothing. It turns for a bit, then stops in the exact same position.

It's a bit of a dead end and I should probably just throw the armature out, but I just wanted to check if you guys have any brighter ideas. I can't find the armature alone for sale and a new starter for this bike is going to be around $250 canadian judging by ebay. hard to spend on a bike that'll never be roadworthy and isn't worth anything running. wondering what you guys know, are the armatures somewhat universal? is a commutator even repairable?
thanks for reading

Firstly you need to clean the spaces between the commutator segments, the easiest way to do this is to break a hacksaw blade and grind it thin enough to fit in the grooves, you can use this to undercut the mica and clear any copper debris (it looks like some of the debris on your armature is "shorting" the segments) you can then follow the below link to test the armature with a multi-meter (a shop would use "growler" to test an armature)

 

 

Thanks for the response!

Before cleaning the spaces I ran the test shown in the video. I found that one of the undamaged commutator bars gives a very high resistance of 35 ohms when tested with adjacent or opposite bars. The rest give 0.3-0.5 ohms. I couldn't set up the hacksaw blade at the time but I cleaned between each of the bars with a dental pick. I ran the test again and now the same bar only gives a resistance of 7 ohms. I reassembled the starter and it ran for about 5 seconds before giving up again.

Given there is obviously damage somewhere should I toss it? I wish I could just replace the armature but I can't find a part number for it or find it alone for sale. I guess I should just buy another starter but I guess I just want to save as much as I can. Thoughts?

wrote:

Thanks for the response!Before cleaning the spaces I ran the test shown in the video. I found that one of the undamaged commutator bars gives a very high resistance of 35 ohms when tested with adjacent or opposite bars. The rest give 0.3-0.5 ohms. I couldn't set up the hacksaw blade at the time but I cleaned between each of the bars with a dental pick. I ran the test again and now the same bar only gives a resistance of 7 ohms. I reassembled the starter and it ran for about 5 seconds before giving up again.Given there is obviously damage somewhere should I toss it? I wish I could just replace the armature but I can't find a part number for it or find it alone for sale. I guess I should just buy another starter but I guess I just want to save as much as I can. Thoughts?

There are shops that will re-wind just the armature (I have included an add from a UK company as an example 

ricksmotorsportelectrics.com/search.php

Hey Guys!

I know it's been forever but I have an update for you finally. I took the armature to a friend who happens to be an electrical engineer. He said that based on the resistances, it's definitely not an internal issue. He said to clean the hooks where the wires touch the commutator bars, and then he would re-solder them for me. He got busy and didn't have time to do it. I was apprehensive about doing it myself because he said to use high-temperature solder which I believe requires a special type of soldering iron. Anyways finally last week I decided to do it myself with a butane soldering iron (which I will not be showing pictures of because I'm not very good at soldering, and I've got the thing completely back together ). I put it to a battery and it spins forever! Going to reinstall it on the 440 once the winter here in Ontario lightens up a bit. It sounds poorly lubricated when it runs, I put some 3in1 oil in it but anyone know what kind of grease to use in it? Thanks!

I'm not sure how my friend knew the issue immediately from the resistances, all I can say is if you're having similar issues with an armature definitely try this, super cheap and in reality super quick if you're confident in your soldering abilities. Use high temp solder if its available to you, my friend said to do so I just didn't have any and I don't really care about the starter to begin with.

Cheers!
www.youtube.com/shorts/fuP9xfhlbFA

You starter motor rpm's in the video is too low whitout any load. He must spin much more higher and should sound like an jet engine.
Sounds like the bearnings and gears runnig rough without any lube.

Alright maybe I didn't fix it then...

I do plan on greasing it up. Any idea what type of grease to use? or does it not really matter?

Apply a high temperature bearing grease.

Scirocco wrote:

You starter motor rpm's in the video is too low whitout any load. He must spin much more higher and should sound like an jet engine.
Sounds like the bearnings and gears runnig rough without any lube.

I would agree that the off load speed seems poor, in my experience this is normally due to one of the below

1. Incorrect assembly (does it turn freely by hand)
2. Poor contact between the brushes and commutator
3. internal armature fault (is there a shop near you that can "growler" test it)
4. Failed field windings

Any of the above will effect run speed and torque output (I suspect if you fitted it to the bike currently it would present as a flat battery (turn very slowly if at all)
PS: be careful flashing the positive terminal like that, you run the risk of damaging the thread. If possible you would be better to secure a lead to it and flash the battery end