[Goober]

Ok recently I saw you all and I think @retro discussing a starter rebuild and I can’t find the thread.

I have an old Trx350 starter been in a box for a few years now and I want to rebuild it. Got it all apart and cleaned up.

Uhhh at the time I was a noob using non OEM stuff so I bought a Quad Boss rebuild kit. I will check the starter out using the manual but the diagrams are terrible for rebuilding! I like to get a few words from experience

 

[retro]

Starter motors are very easy to work on Goober, but yours has a bad commutator on the armature unfortunately. Its too far gone to put on a lathe and fix... the armature will need to be replaced. Other than that issue, your kit should work just fine.

 

[Goober]

Thanks Retro
Bummer oh well it was an old one from another build; now that I remember I thought the guys at the shop told me it was no good.

The commutator looks rough. So is it ready for recycling? I just may save the whole thing in case I need an end housing. Here’s some more pics.

 

[retro]

Ya, its worth saving for parts. Who knows, you might spot a cheap starter with a decent armature in it someday? If you had absolutely no other choice (Mad Max scenario) you could chuck that one up on a lathe and cut the commutator down level again. But the motor life would be short if you did that... the brushes would fall out of the brush holders as soon as they wore about halfway down and brush spring tension would be under spec'd right from the git-go. Continued use of that starter motor while the brushes were shot (severe arcing eroded the copper bars) is what ruined that commutator.

 

[Goober]

Hmmm I need to inspect/rebuild another starter.
What signs do I look for on a weak starter?

I have one that will barely spin; I thought the compression release was out of adjustment

 

[retro]

Well, a dry nose bearing and dry/worn rear bushing will make them drag quite a bit. Brushes worn too short, a stuck brush in a rusty brush holder, a burnt/overheated brush spring, or a burnt off brush lead will leave them incapable too. So its usually bearings or brushes issues that kill them. If the commutator looks good in your next teardown, use a multimeter to check the commutator bars as shown in the manual. If those check out OK then its rebuildable... and its a pretty straight-forward new parts swap/reassembly after that step.

Count the shims at each end of the armature (better yet, separate the shim stacks and mark their location) when you take the motor apart so you can put them back as they were. Those shims center the armature in the field magnets' magnetic flux and control shaft endplay.

Never sand or buff off the dark coating of graphite on the copper commutator bars when rebuilding the starter, as that thin graphite layer is a solid lubricant for the brushes.

But if the commutator is slightly damaged by brush arcing, but checks out fine with the ohm meter, you can chuck the armature in a lathe and cut up to .012" off from the bars to smooth & relevel them. An auto-electric shop can generally turn them for you quickly and cheaply as long as they can be cleaned up with a couple shallow passes on the lathe. They'll turn ya down and sent you away if commutator damage is excessive though.