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Monday, February 20, 2017

Triumph Spitfire Engine Rebuild #11 - Starter Motor

I decided to split out my previous #11 post that was a bit of everything into discreet posts. This is for the starter. I have one for the generator, distributor and water pump and body right now that are in progress because the work is still in progress. Some new stuff towards the end in this post, though, so it won't be a total waste to read again.

I have three starters in total. One came on the car and two came with it. I tore into the one on the car first. Lots of evidence of its age. I'll be referring to numbers in the diagram below to keep the discussion as clear as possible.

Exploded view of the starter.

Electrical end of the starter with the cover band (8) removed.

These are pretty simple machines that come apart rather easily. The two through bolts (24) sandwich the entire unit together and attach to the end bracket (14). The terminal nuts (1) are where the cable connects from the solenoid on the bulkhead to the starter. I removed the two bolts (24) and slid a putty knife in between the end bracket (14) and the yoke (23) to separate them. The rotor pulled out of the yoke with the end bracket and drive pinion assembly (16-21).

View of the internals. Brush rigging is clearly visible at the bottom.

To free the rotor requires removing the starter main spring (18) and pinion and barrel assembly (21). To do this, the main spring must be compressed to get at the jump ring (16) so that can be removed from the end of the rotor shaft (13).

For this, I used the vise for one side and a pair of vise grips for the other. A small flat head screwdriver pried the jump ring from the shaft. This was not a great solution as I bent up the jump ring a bit.

The compression scheme. Not the best way, but it worked.

The entire assembly removed.

To remove the other end of the starter, where the brushes are, I used a putty knife to separate the end plate (4) from the yoke. This revealed damage to the braided copper wires that the brushes attach with. Unlike the dynamo (generator), the starter does not have easily replaceable brushes. They are soldered or riveted to their particular contact points. While this starter did work, I wanted to investigate the other two in case one of those was a better candidate for refurbishment.

The brush end. A good amount of damage to the brush wires here.

As an initial check, I came up with an ingenious rig to do a quick operational test of the other two starters (lucky I didn't blow myself up!) and both rotated.

Simply touch the negative braided cable to the starter body and...rotation!

I began with the starter that appeared to be in better shape and, lo and behold, it had been refurbished at some point, though it took until I got to see the insides to figure it out. Several parts of this starter were different, many with an improved design that improved on ease of maintenance. It appears that several starter model numbers were used for Spitfires and design changes were made throughout.

For this starter, the end of the shaft was threaded and the retainer (17) was a slotted nut that screwed down on the shaft. A cotter pin provided vibration protection. Much easier.

A blurry picture of the upgraded starter pinion gear assembly.

Along with the cover band, tape was used to prevent foreign material from entering the starter. Upon removing the tape, it was obvious that the starter had been refurbished in the past.

Much cleaner inside, along with new brushes and a painted interior.

I wanted to get the stator out so I had to remove the pole securing screws (10). These were in there pretty good so I used my breaker bar and a large Phillips head socket screwdriver. I had an impact screwdriver standing by just in case, but I didn't need it.

Weapons of choice to remove stator.

Removing the stator and end plate.

The stator pole pieces are wrapped in a fabric tape, which, unlike the starter from the car, was in good shape thanks to the previous rebuilt. I need to look into this stuff because the other ones need to get re-wrapped if I want them as spares. Once that stator was removed, I took a wire wheel to the inside and outside of the yoke (23) in preparation for paint.

Various identification information. Made in December of 1965...close enough!

Primed. Two coats of primer, two coats of low gloss black (same as engine).

 I removed the stator brushes from the end plate to allow for easier clean up.

Close-up of end plate showing brushes.

End plate with stator brushes removed.

Everything all cleaned up and ready for assembly.

A piece of insulation paper came out of the starter, so I wanted to put this back in the correct spot. It was where the terminal came out so I assume this was to prevent incidental contact between this and the yoke since they should be electrically isolated from each other. Like the stator wrap, I have to do a bit more research on this stuff since I expect the other starter's paper to not come out in salvageable condition.

I used the Gasgacinch stuff again because it was handy and probably a good choice.

I let the Gasgacinch cure for a bit, then installed the stator. For this yoke, there was a "dot" where the terminal post comes out, but it was also keyed for the end plate, so re-assembly was almost a no-brainer.

Key and "dot" markings for orientation.

Next up was rotor installation. To prevent chipping any brushes or marring the commutator, I set the springs against the brush boxes so they didn't put tension on the brushes, allowing them to set out and provide room for easy rotor installation.

Spring set on the inside of one of the four brush boxes.

Once the rotor was in, I used a small hook to pop the springs back over the brushes.

Almost all back together.

All that remained prior to testing was to install the main pinion/barrel assembly and secure it with a new cotter pin.

The appropriate cotter pin for my situation.

Then, a quick test verified that everything was operational, including operation of the pinion. I left the cover assembly band off so that I could check the brushes for excessive arcing and sparking.

After that, I used Loctite Thread Locker BLUE 242 on the pole securing screws to keep them nice and tight.

Loctite 242 makes a cameo.
 Finally, I put the cover assembly band on to make it all nice and pretty and she was done.

All done and ready to go on the car...eventually.


  1. I suddenly find myself in a situation where I need to investigate and possibly rebuild my starter as well. Thanks for this post; between it and the manual I will hopefully get to the bottom of what's wrong with mine...

  2. Thanks. I hope it helps you out. Hazen was not having fun with his starter lately, either. I'm glad that I had basic motor/generator theory in the Navy...helped with understanding how these simple machines work.

  3. I'm a software guy so all this "hardware" stuff is new to me. But I am decent at figuring stuff out. See also my recent YouTube video... I found interesting things behind my starter, e.g., https://youtu.be/AWzC3BO2OuU

  4. Wow. Yes, definitely a critter or two in there. Not sure how they got in, though, unless the starter was out for a time. Maybe a chipmunk?

  5. Chipmunk - that's the animal I was trying to think of during the video. I obviously don't speak well on my feet!

  6. Ah, so you have the M35G, and I have the M35J... different model, and it's not described in the manuals that I have. No idea how different they are, but even getting it open is a different procedure, not described... Argh.

  7. How did you wire wheel the yoke? Every time I try, it rolls away! Hehe

  8. I did a similar bench test of my starter today and it worked!

  9. Good deal! It's like doing small parts of a big puzzle. Get all the parts done and step back...there's a car!

  10. Heh. Today the challenge was getting the circlip back on... still not sorted. Even tthough a vise grip plus a plumber's wrench was enough to compress the spring to get it OFF, nothing worked for me today to put it ON... I also tried using a vise (though only on one side.)

    1. I don't remember what I specifically did there. But I do remember it being painful and being worried that I was going to ruin something. Good luck!