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MG Midget and Sprite Technical - Bendix and ring gear

The ring gear and Bendix are worn pretty bad on my '72 midget. The starter works fine, and I have no intention of going to a high torque model.

I ordered a new ring gear, and found a very good Bendix in my parts box.

Can I use a slightly used Bendix with the new ring, or do I have to replace in pairs?

How do I remove the Bendix from the starter? There must be a special tool, where can I find one, or should I just bring them to a starter repair shop?

Thx, Phil

P Burke

Phil,

The Bendix assembly is held on to the shaft via a snap ring. This ring can be removed by taking some of the pressure off of the big spring which I did using a large C clamp. I know, it sounds Mickey Mouse but it worked. The hard part is keeping the clamp lined up while you tighten it. You can try any other method that works for you. Once you've got the pressure off of the snap ring you just pry it of. To reassemble it, I put everything together, stood the starter upright and used and old socket that fit over the shaft and just tapped it until the ring popped into place.

Over the years I've gotten very creative in performing some operations due to lack of access to "proper" tools or equipment. Since most of these repairs are a once in twenty years type of job, it's easier to do it this way than spend days waiting for some over priced tool to show up. Plus it's a mental challenge.

And your Bendix looks pretty good. Just make sure it has the same number of teeth as the one you're replacing.
Martin Washington

Are the 9 tooth and 10 tooth Bendixs interchangeable? I know both were used, and they both fit my flywheel. Also. there is only 1 flywheel/ ring gear listed...
P Burke

For 5 bucks... id let the electric motor shop do the deed

Hmmm, maybe thats why they are not business any longer. :-)

Seriously... it cheap to have done and fairly common

The ring gear... my understanding is there is enough gear slop that ither the 9 or 10 tooth can be used without issue...id probably go the 10 tooth just because it would be less slop and better contact between teeth...just me!

According to david lieb, he put the flyweel in the deep freezer for 24 hours and stuck the ring gear in the gas powered BBQ grill for a couple of hours then mated the 2 togather

Heat/ cold....expansion/contration ...its in the archives if you get bored sunday afternoon

Prop
Prop and the Blackhole Midget

The 9 and 10 tooth gears are "interchangeable" but....

I had the 9 tooth one in my car and it would occasionally not disengage. I put the 10 tooth one in and I've not had the problem since.
Martin Washington

Prop,

I assume from your comment "id probably go the 10 tooth just because it would be less slop and better contact between teeth...just me!" that you think the 9 tooth will be smaller than the 10 tooth. I can't say for sure but I know that in automotive applications the numbers of parts are large and often the tooth profiles are adjusted to give correct running clearances, basically the tooth profile of one of them is not likely to be a standard gear profile, maybe neither is.

A mate that works in automotive engine design ran into this when asked to look at a gearbox, later a gearbox expert came in and said not to bother using standard gear tooth sizes as the numbers involved in production meant that they could make whatever they wanted to optimise the gear for the application and save money.
David Billington

Neither that ring gear nor the bendix gear are especially badly worn. The corners of the ring gear teeth are chamfered off when new so what looks like a lot of wear isn't really. What does happen though is that the ring gear wears more in one particular patch of maybe 4 or 5 teeth as the engine more often comes to rest in the same position. Your photo may not be showing the worst bit.

Changing the ring gear is one of those one-shot jobs that takes a bit of confidence as it needs to go on right first time. You don't get a second go at it and cannot do a practice run! That said, I found it was a lot easier than I anticipated and very satisfying that it worked like text-book!
Guy W

David,

Im not sure what your point is. Its just my personal opionion and NO I cant back it up factually that the 10 tooth gear is a better choice over the 9 tooth as both will do the job, I just think the 10 tooth has less gap filler space and more metal on steel contact... thou I could well be wrong, its just an assumed opinion I have

Prop
Prop and the Blackhole Midget

They both look worn enough to me to be replaced.
I have a good 10 tooth gear from a starter that failed soon after install.
Comparing them, the wear looks substantial.

The motor is out and sitting on a table. I've had the new clutch and rear seal kit paid for and on my shelf for 1 1/2 years waiting till I had time to pull it. I'm willing to spend $30.00 plus install on a new ring gear and labor to swap my Bendix gears.

P Burke

And the Bendix
Note the 10 tooth on the left has narrower teeth than the 9 tooth on the right...

P Burke

Phil,

I tend to agree with you about the wear. Almost surprising that they still worked. And like Guy says, they like to stop in the same place thus wearing out the teeth in one spot. When mine failed the Bendix wouldn't engage unless I put the car in gear and rolled it a bit to turn over the engine so that I had good teeth on the ring gear lined up with the starter. I also believe that this situation was made worse by having a 9 tooth Bendix when I should have had a 10 tooth one. If I'm not mistaken, the 9 tooth went with the smaller engines since I used the starter on my 1275 from the 948 that came with the car. Someone who has access to archives could look and see if that's true.
Martin Washington

$30 bucks... thats a no bainer , id pay $30 just to not have to wash my hands afterwards

:-)

Prop
Prop and the Blackhole Midget

Assisted with this operation only a fortnight ago. It was a Ford Sabre diesel from my mate's boat.
As Prop said the freezer and in this case the oven were our friends, But as Guy says you need to get it right first time. But it looks scarier than it is really.

In our case the starter was completely f++++d anyway so we fitted a new one, so the bendix question didn't arise. And it's pre-engaged anyway.

As Guy says practically all engines "park" in the same position when they're stopped leading to uneven wear and stress on the ring gear. I can well remember putting cars in gear and rocking them to help the starter find intact teeth on the ring gear. This is a remedy that can work for years and years!
RS Hughes

Couple of bricks on the kitchen floor.
2 pairs of pump pliers or similar
hammer.
Flywheel in the freezer - make sure the edge lip to receive the ring gear is clean and uppermost!
Ring gear in the oven about 400F - and make sure it too is the correct way up ready to drop down onto the flywheel

After about an hour or so you go and grab the flywheel out of the freezer and set it down on the bricks, next to the oven.
Swing open the oven door, grab the ring gear with the pump pliers and drop it onto the flywheel. Use the hammer to quickly tap it down so it seats snugly and evenly all the way round. Actually, even in contact with the ice-cold flywheel the ring gear didn't shrink down quite as fast as I expected and there was more time for adjustments than I needed. It also didn't really need hammering down either - it just set on properly first as it was. But it made me feel like I was doing something skilful!

Oh, and you remove the old ring gear with a sharp cold chisel between two teeth. A couple of (skilfully aimed !!) hammer blows will split the ring. If it is stubborn make a small nick between two teeth with an angle grinder/ dremel/ hacksaw - just acts as a stress raiser and help the split to start.
Guy W

One of my first ebay purchases was a starter motor bendix spring compressor.

There is a John Twist video where he uses two pairs of mole-grips (vise-grips) to compress a bendix spring. It looked a highly dangerous operation.

I've just found this photo of a compressor on t'interweb. It looks just like the one that I bought.

Dave O'Neill 2

It must be good... ive seen that tool also in electric motor rebuild shops

Prop
Prop and the Blackhole Midget

I probably could build one of those out of a couple of fender washers and bolts!
I guess it's worth a buck at the hardware store to try.
P Burke

When I had to change the starter on our 1380, the replacement came with a 10T pinion. The immediate difference was in how fast it cranked the engine over.

10/9 = 11% faster, but very noticeable.

P.S. It does have an 075 battery, so lots of 'cold cranking amps' if the starter can make use of them.

Richard
Richard Wale

This thread was discussed between 04/06/2015 and 07/06/2015

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