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MG Midget and Sprite Technical - Midget starter motor: bendix teeth

The starter in my 1978 1500 midget is starting to stick/jam. (Had to engage gear and push car to free it).

I've just been doing some Googling, it seems there is a choice of either a 9 tooth or 10 tooth bendix? But there is scant information as to which version fits which vehicle? Information is all very vague.

Does anybody know why the two bendix versions exist?
J Thomson

Whilst you wait for more knowledgeable replies.

Why Google when you have the Archives here, first thread I looked at has, Greybeard – “the extra tooth turns the engines slower, not faster, but with about 11% (IIRC) more torque.”

So there you go for that.

For the rest you can look as I don't know but if you order a starter that is suitable for a 1978 Midget 1500 then provided
. your battery is in good condition and well charged
. and all electric connections and earths are in good condition
. you use suitable engine oil with timely changes
. it's for a standard road car with standard road car use
then 9 or 10 doesn't really matter.

There'll probably be some supporters in each camp but you'd want users to match your car use.

The staters probably varied as they're probably be used on other vehicles too.

Have a look in the Archives if you want to repair your present starter or perhaps see if there might be other causes or solutions.
Nigel Atkins

"Greybeard – “the extra tooth turns the engines slower, not faster, but with about 11% (IIRC) more torque.”

Wrong! The 10T starter pinion turns the engine ~11% faster, with ~11% less torque!

The answer about which engines they were fitted to is that there is no answer. Both 10T and 9T pinions can be fitted to any A-Series engine. I first came across the 10T pinion when buying a new starter for our 1380 about 10 years ago. The increased cranking speed was immediately noticeable, but I suspect helped by having a large capacity battery (60Ah, 590CCA).

I was not offered a 9T, the 10T was all that was available from the supplier at the time.

Replacing the 10T last year, and reverting to a 9T, the reduced cranking speed was noticeable. This time only a 9T was available.

If a choice is available, I would definitely go for the 10T PLUS a large capacity battery to get the full advantage from it.

Theory says that you cannot mesh two different sized pinions, on the same centres, with the same flywheel ring gear, but in this case you appear to be able to do so!

Richard
Richard Wale

Richard,
by coincidence I also saw a post by you when looking in the Archives but sorry I misread your post as being the same as Grey's (he's a naughty boy - but he did put IIRC which I included).

Your engine and battery aren't standard so you may gain more by 10 teeth more than others.

"Both 10T and 9T pinions can be fitted to any A-Series engine" does this also apply to a Midget 1500?
Nigel Atkins

The ring gear determines the pinion teeth - the 1500 Midget has a 117/10 ring gear, so 117 teeth on the ring and 10 on the pinion.
Chris at Octarine Services

Re. 9 teeth or 10 teeth starter bendix gears. My findings:

The A-series engine cars were made/supplied with the 10 teeth bendix starters. Starter motor: GXE4405. Bendix: BAU5781.

The 1500 Midget (Triumph engine) was supplied with the 9 teeth bendix starter. Starter motor: GEU9405. Bendix: 67H5010.

LRS101 is the original part number for GXE4405.

My feeling is that the tolerance is so loose for bendix/ring-gear tooth engagement that suppliers simply treat the 9 teeth and 10 teeth bendix variants as the same part.

Without studying the tooth dimensions of the respective vehicles' ring-gears (life is too short LOL), it appears to be an academic point. Possibly the 10 tooth bendix creates quicker ring-gear wear in the Triumph engine, likewise worse wear will result with the 9 tooth bendix when used on A-series engines. All academic, I guess.

J Thomson

Did I write that? Good grief.. OK I'll put my hands up. It was a long time ago but still a bit daft.

10 teeth on the bendix is correct as Chris said. Would 9 teeth work? Dunno. Probably but not ideal.

The 1500 starter is otherwise interchangeable with one from a 1275 AFAIK. It'll also fit a Triumph 6, and a Mini if you swap the face plate.

The sticking issue might have nothing to do with the bendix teeth. It may just need a severe cleaning. The spiral spline that the bendix travels on needs to be super clean and - crucially - oil-free or it won't return properly to the rest position.
If you want to use a lubricant a light spray of PTFE lube is okay as long as there is no oily residue. Dirt and clutch dust will stick to oil and you're back to square one.

But the absolute first thing to look at is the mounting bolts. If they are even a tiny bit slack the motor will run out of true and jam as you described.
I have a spare starter with a 10 tooth pinion if you get stuck.
Hope that helps more than my previous nonsense!
Greybeard

It's not likely due to sloppiness of the pinion fit with the ring gear but rather the tooth profile of one of the pinions has been altered to give correct tooth engagement even if the tooth profile isn't an ideal involute profile.
David Billington

Unless the information that I have to hand is wrong, the 1500 Midget starter motor is GEU9405, which has a 9 toothed bendix?

J Thomson

I discovered that there's a choice between 9 and 10 teeth when I replaced the starter on my 1967 Sprite a couple of years ago and I got the wrong one!

I can't remember which way round it is, but I know I spent some time with the motor factors poring over catalogues before we came up with the part number for the correct one.

The problem wasn't with the gear teeth, it was something else that I can't quite remember, save that it just wouldn't fit properly. It is coming back to me in a vague sort of way that, with the top bolt in place, it wasn't possible to get the bottom bolt in.

Back on the factor's bench with the two side-by-side, there was a definite difference.

I might have the part numbers somewhere - I'll start hunting.

Edit: Can't find the invoice where it's supposed to be - what I do remember is that the correct one was more expensive!
C Mee

My 1976 factory parts catalogue has starter M35J (25149) 13H5798 so cover the Midget 1500

67H5010 shows as Pinion and barrel which may be backwards compatible to starters A to H 25079

Earlier starter but should be the same stuff relevant - https://www.youtube.com/watch?v=kmh2qZgfv1Q

I can remember some threads and some question but not often can I remember what the answer was.

Perhaps here it might be 9 teeth for 1500s and 9 are backward compatible if you can't get 10 (or want 9) for earlier models (of course the body fitting would have to be correct)?

The 35 is for 3.5", wonder if I'll remember that now, but I didn't before.
Nigel Atkins

NMC- but - Back in my yoof we all had Anglias and some rich kids had Cortinas, - Both, especially the Anglia ,were prone to the starter locking in and you either rocked the car in gear or got your spanner out and wound the end square on the starter to get them unlocked, both had 9 tooth pinions and the fix was to fit a 10 tooth, Everyone said they wouldn't fit, "it'll be too big and jam" but they fitted and worked perfect
Before I put one on my Anglia, I found that if the ign points were good and adjusted up the starter wouldn't jam, but as soon as they closed down a bit it would be harder to start and started jamming----beats me why but there you go

willy

William Revit

I always thought that 10 and 9 tooth starters were interchangeable. I believed that both fit because the pinions are the same diameter, with the 10 toothed one having a slightly slimmer teeth. They work with the same ring gear because the mesh is pretty sloppy anyway. I have certainly used both on my 1275, though not at the same time.
GuyW

Gets even more confusing!

Looking at the BMC Parts Manual (AKD3566) for the Sprite MkI to Sprite MkII/Midget MkI and the BL Parts Manual (AKM0036) for Sprite MkIII/Midget MkII to Midget 1500, with the exception of the very early Frogeye, which was superseded by the later part number, the part number for the pinion/barrel assembly is the same for all models - 67H 5010. No mention of number of teeth in either of the manuals.

Using the 2 part numbers above - GXE4405 and GEU9405 - in Google produces no consistent picture at all.

In various websites both are listed as having both 9T and 10T and both are listed for some or all Sprite/Midget models.

I suppose the 'official' manuals that use the same pinion part number throughout the Sprite and Midget's life should be reliable?

I have searched through Google for pinion 67H 5010 and of the illustrations that show the teeth clearly, they are all 9T!

How/where does the 10T pinion come into the frame?

For the complete starter motor, the part numbers are:

3H 952 Early Frogeye - superseded by
13H 559 Later Frogeye through to 1098 and ?1275 - No changeover date given - superseded by
13H 5798 ?Late 1098/1275 through to 1500

In effect the same starter was fitted to everything from Frogeye to 1500, but no mention of number of teeth in the 'Official' Parts Manuals.

Richard
Richard Wale

In the JT vid I put up he's dealing with a M35G from 1958 (off an MGA) so the G is from at least 1958.

I've no idea if there was an I but ours seem to be J, for the later cars at least.

Later today I'll drag out my CD-ROM and see if I can hand crank it to work and look at the factory parts catalogues on there (possibly to discover less information than Richard has already put up).
Nigel Atkins

I always thought that 10 and 9 tooth starters were interchangeable. I believed that both fit because the pinions are the same diameter, with the 10 toothed one having a slightly Wilberforce teeth. They work with the same ring gear because the mesh is pretty sloppy anyway. I have certainly used both on my 1275, though not at the same time.
GuyW

I'm guessing here, but I'm thinking that the confusion comes because the 1500 Midget engine is a Triumph unit. The engines in Midgets prior to the 1500 are A-series derivatives?

(I do agree with Chris@Octarine, the 1500 ring-gear has 117 teeth - I've just counted them from my year 1978 1500cc ring-gear. But I'm sure the bendix was originally 9 teeth for the 1500cc).

My feeling is that the (now long established) recommendation of a 10 tooth bendix starter for the 1500 is merely a 'supplier convenience'.



J Thomson

My short answer (to original post) -

. Midget 1500 - 9 teeth (but you could used 10)

. the various starters over the years went on to a range of different vehicle, some starters had 9 teeth some had 10.

Longer answer to follow.
Nigel Atkins

Well I have just dragged out the 2 Midget starter motors I have in stock and they are both 10 teeth on the pinions.
Chris at Octarine Services

What numbers on them Chris?
Nigel Atkins

TLB 111 is also listed as the pinion for Midgets and MGAs which makes sense to me as the MGA ring gear is 120/10 teeth.

In fact all MGs from TD onwards have 10 pinion teeth except the V8 which has 12.
Chris at Octarine Services

They are Lucas 25148 dated in 1970 and 1978 - M35J
Chris at Octarine Services

Chris was 25148 a typo for 25149?

And was there a B on the end, or have you any idea what the B would mean if it was there?
Nigel Atkins

Not a typo - the Lucas 25149 is an LRS101 9 tooth starter - but some people list these for the Midget as well.

One is 25148H dated week 47 1970, the other is 25148E dated week 24 1978
Chris at Octarine Services

Chris,
I'm not saying you're wrong just that the modern listings and cross-reference tables (that are often wrong) I've only found Ford (Escort/Cortina) for 10 teeth, LUCAS LRS100/25148 - but - they also reference a mix of similar Rover numbers Moss use.

Modern lists and starters available seem to be a mix as everything seems to melt into each other.

Just as (one of each) examples of cross-referencing -
LUCAS LRS100 10 teeth - https://www.heritagerotating.co.uk/product/lrs100-ford-cortina/

LRS101 9 teeth -
https://www.autoelectricalspares.co.uk/111103-starter-motor-replacing-lucas-lrs101-m35g-116-p.asp

Looks like BL side is wedded more to 9 teeth now (with options or availability of 10) but Ford side (and others(?)) (and 3 bolt fixing?) to 10 perhaps.
Nigel Atkins

SC Parts UK - their catalogue is pretty extensive.

Shows the 25022 & 25079 with 9 teeth and the 25148, 25149 & 25233 with 10 teeth.

I am not saying I am right or wrong - just that 2 starters I pulled from Midgets are 25148s

Note the 9 tooth ones are M35G and the 10 tooth ones are M35J.



Chris at Octarine Services

Just one other observation and confusion - LRS numbers are Lucas recons and could have any old casing stamped totally irrelevantly. The factory parts numbers don't necessarily relate to any one spec of starter.

Lucas would have made changes to the internal specs of their units and changed the Lucas part number without it affecting its application - so the engines division of BMC would have received a batch of starters from Lucas possibly with a range of Lucas part numbers.
Chris at Octarine Services

Here are a couple of pages on the subject of gear tooth profile shifting. Looks like the 9 tooth might be the more likely candidate in order to increase tooth strength.

https://khkgears.net/new/gear_knowledge/abcs_of_gears-b/gear_profile_shift.html

https://khkgears.net/new/gear_knowledge/introduction_to_gears/profile_shifted_gears.html
David Billington

Chris, I wasn't thinking any of us on the thread were right or wrong, too confusing to tell. The starter motors now seem to be like many Spridgets outwardly looking the same but with many different combination of parts from different times.

Moss offer "PINION BARREL & SCREW, 10 tooth" parts to both 25022 and 2079 (B) - and to 25149B and 9 teeth parts to all three too.
https://www.moss-europe.co.uk/shop-by-model/mg/midget/electrical/starting-system/starter-motor-sprite-iv-midget-iii-1500-1967-79.html

This from Rimmers site only as an example to give the idea (and confusingly has M35G 1(?))
"TR250s were fitted with Lucas model M35G-1 starter motors. The factory replaced the early design (which had radial brushes contacting a ‘side’ commutator) by an all-variants-encompassing starter motor of the later design (with axial brushes contacting a face commutator). The net result was two starter motors of clearly different construction which were, in fact, interchangeable. They may be identified by the following:
Lucas Type M35G (original Triumph part no. 200535): Stamped with Lucas no. 25022 or 25079, plus suffix between A and H.
Lucas Type M35J: Stamped with Lucas no. 25149.
If you wish to repair your own starter motor, you must identify which type is fitted prior to ordering spares for it."

Of course all databases (catalogues) have errors and omissions.

Just out of interest flywheel ring-

948cc - 104 teeth - AEA596 - UB104/10R

1098cc - 104 teeth - 12G290 - CBS104/10R

1275cc - 104 teeth - 12G1444 - CS104/10R

1500cc (and bigger engined Triumphs) - 117 teeth - CB117/10R

I've yet to look at my CD-ROM for starters but I doubt if they'll be different to what Richard has already put.

Sorry David I wasn't ignoring your post, but as you know far too technical for me.
Nigel Atkins

I can tell you that a 10 tooth pinion is a very nice snug fit as it rotates on the ring gear teeth for a 1275 engine and also the larger ring gear for the 1500.

My preference would be to fit the ten tooth pinion since clearly the ring gear is made ( and specified ) for it.
Chris at Octarine Services

One of my race Midgets didn’t want to turn over when the engine was hot. It had a 10 tooth starter. I replaced with a spare that I had, which had a 9 tooth pinion, and it cured the problem.

Many years ago, I had a short stint working for a company that reconditioned starters and generators. There was no discrimination between 9 or 10 tooth pinions when reassembling.
Dave O'Neill 2

The only thing I can add to what Richard put is, starters -

13H 559 - M35 (A-H) - (25079)

13H 5798 - M35J - (25149)

Nigel Atkins

Dave,
where were you earlier! I've been hand cranking an old CD-ROM as 78 revs per hour looking for info.

So there we have it, 9 or 10 is luck now.

We'll have tear down those concours cars and check the starter casing details.
Nigel Atkins

Well there we go - the reason some starters have 9 and others have 10 is because Dave mixed them all up!
Chris at Octarine Services

Wouldn't it be easier just to ask for a 10 tooth then you'll get one, instead of confusing the poor old parts guy with a truck full of numbers
William Revit

OK, I’ll take full responsibility.
Dave O'Neill 2

Leacy Classics list a starter motor with given number of teeth (10) using the Unipart (British Leyland's own aftermarket parts division) number GXE4405 and for all Spridgets models and all years:
http://www.leacyclassics.com/parts/mg/midget/electrical/gxe4405.html

(Leacy also list just the drive gear for the starter motor - a 9 tooth one! Out of stock at the moment: http://www.leacyclassics.com/parts/austin-healey/healey-sprite/electrical/67h5010.html They also list the spring: http://www.leacyclassics.com/parts/austin-healey/healey-sprite/electrical/7h5045.html)

Dave

Sounds like you did some sound development and production engineering when rebuilding!

I wonder what rebuild companies today say what fits, what is available and what they supply as either exchange unit or rebuilding the customer's own starter and returning it to them?

Cheers
Mike
M Wood

Ran out of time to add to my post above.

Minispares also sell a starter motor with a given number of teeth (9) listed under Unipart number GXE4404, note this is a new starter so the Unipart number is just that, a number for reference not a Unipart part:
https://www.minispares.com/product/Classic/Electrics/Starters/GXE4404.aspx?0911&ReturnUrl=/shop/classic/Electrics/Starters.aspxBack%20to%20shop

So looks like in Unipart land the 9 tooth model is GXE4404 and the 10 tooth model GXE4405.

But I have not bought either recently so cannot compare what was in each box, also note to test this theory of Unipart numbers and actual parts they would have to be new old stock Unipart parts (and from experience years ago, that may not be bulletproof either as Unipart was a supplier not manufactuer).

Note in the Minispares listing for GXE4404 9 tooth starter had some interesting text on the subject of the number of teeth:

Brand new Inertia starter with the correct 9 tooth pinion for all minis up to the fitment of the pre engaged type in 1984/5. Do not fit the 10 tooth starter sold by many as it can ruin the ringear or the bendix. Other leyland cars used 10 teeth such as Sprite, Spitfire and Mini Metro and often get fitted ass they are cheaper but 9 teeth is rarer to buy but is meant for Mini 107 teeth ringears

Brand new units these are sold on an outright basis without having to return your old unit. Perfect for overseas customers or classic car owners wishing to retain their original for rebuild at some stage as the donor units are now becoming very rare as they have not been fitted to production cars for over 20 years. These are closer to the later 35J type. Early cars had 35G starter which had different internals and the body usually had stamping numbers 25071-25075 or 25083 which used GSB102 brush sets.



Note that I have not bought these parts recently from either supplier so cannot give my experience of what was supplied.

Wish I had an old copy of a Lucas starter motor catalogue that cross references many numbers from a range of manufacturers and suppliers for every car model (Lucas, OE factory number, Unipart etc)
Thanks
Mike
M Wood

Not sure what the difference is between a Unipart GEU9405 (that the OP in a later post identifies as a 9 tooth model for Triumph) and a GXE4404 (which Minispares says is 9 tooth model, noting that in Mini land there are only A Series engine cars and we are talking up to 1984 for bits like this).

I am confusing myself before breakfast.

Mike

I hate being an 'Internet Mechanic' only at the moment!

M Wood

Mike

Minis will always have a different part number to Spridgets, as the end bracket has different mounting hole centres.
Dave O'Neill 2

Good sleuthing Mike, I was more trying to find what was original compared to the usual suspects supply today.

Nowadays the parts numbers mean very little and the cross-referencing lists of numbers can be very tenuous with lists being copied and amalgamated as stock depletes and production rationalisies.

I don't know if I'm strictly right as I forget and don't used the numbers enough but I take the XE as rebuilt exchange or just rebuilt but even then it might refer to a new built item (but does that have all new parts or case reused? or both or either, as in stock).

The Mini Spares GXE4404 is a good example, if that is normally a rebuilt or exchange part number, they clearly state it's a brand new unit sold outright.

I notice the Mini flywheel is 107 teeth

This all seems to be Dave's fault and his past nefarious activities. Look at the comotion your indiscretions have caused!
Nigel Atkins

Willy,
the sort of places that could do that are few and far between, most of the suppliers would have to open the boxes or go through the stock and it'd be as much a mystery to them as to which numbers or boxes have the 9 or 10 teeth (excluding the Mini Spares one).

Blame DaveO, I am.
Nigel Atkins

Nigel, I just went to a scrapyard and found one that looked the same! No idea of the numbers though. It had slightly different looking teeth on the Bendix, and either more or fewer teeth, but fitted and worked just fine.

I do seem to remember that one starter used a collar or shim between the motor flange and the backplate. Unless that was on the 1500.
GuyW

Yes scrap yards in other parts of the country seem to be run differently to here and perhaps staffed differently than here, bit of a closed shop, I'm not sure what other business activities they have but strangers to the yards here seem to be viewed with a lot of suspicion - but I've not been to one for years.

I think that's the point that the starters are all basically the same, other than fixing for various makes and models - or if you're keen on a particular number of teeth.

I think the thread has just reinforced that part numbers are used loosely and cross-reference lists have to be treated with caution.

I bet Dave's old recon company had close links to some scrap yard. (Wink, know wot I mean).
Nigel Atkins

Guy

Yes, it's the 1500 that has a spacer.
Dave O'Neill 2

Spacer and shim - the 1500's backplate is much thinner than the A & B series ones.


Chris at Octarine Services

Just as I remembered Chris. Just couldn't remember which of my cars it was on. It was a while ago now!
GuyW

This thread was discussed between 22/05/2020 and 24/05/2020

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.