starter motor

[PAULJ]

Hi all, Ive just bought a very nice second hand starter motor the bloke says came off a 1970 moggy. The problem it has 10 teeth now I know the one I have on the van is 9 teeth. I have questioned this and the bloke says it came off a moggy so that's that. Now I could be wrong but surly if it has 10 teeth the pitch would have to be different so wont mesh with the gear or am I wrong ??
Cheers

[IslipMinor]

Bizzare as it seems, the 10T pinion meshes perfectly well with the original flywheel ring gear. With some knowledge of gear tooth forms etc., I cannot see how that is, but it works!

About 10 years ago we needed to replace the starter on our 1380 engine (uses the same starter as the 948/1098) and like you was offered the 'later 10T' version. I questioned it and was assured that it was correct.

With a 60 AH battery and 11% more (starter motor) cranking speed revolutions, the engine spins over very quickly, no matter what the temperature is. Good 'upgrade' to have.

[bmcecosse]

There are 11 % less starter motor turns to revolve the engine one turn...... I believe there are also 11 tooth bendix starters around - but certainly the 9 and 10 are interchangeable.

[PAULJ]

Thanks for the reply. You would think to keep the same pinion circumference the pitch would be different. Ill take your word for it but just cant see it
Cheers

[mike.perry]

A combination which definately does not work is 80T flywheel Morris 8 and Military generator engines among others. The Series MM flywheel should have a 102T flywheel. I found this when I fitted an engine with the wrong flywheel. Changing the side valve flywheel involves removing the engine, dropping the sump and removing the main bearings to drop the flywheel.

[PAULJ]

A combination which definately does not work is 80T flywheel Morris 8 and Military generator engines among others. The Series
MM flywheel should have a 102T flywheel. I found this when I fitted an engine with the wrong flywheel. Changing the side valve flywheel involves removing the engine, dropping the sump and removing the main bearings to drop the flywheel.

Well that sounds like lots of fun I should have mentioned that its for the camper van. That has an MGB engine. Ill take the 9 tooth motor off and if the 9 tooth pinion meshes with the 10 tooth it should work. Ill ask on the other forum.
Cheers

[IslipMinor]

There are 11 % less starter motor turns to revolve the engine one turn

Yes, that is what I meant! I.e. for the same starter motor speed the engine will turn 11% faster with the 10T pinion.

[bmcecosse]

The tooth profiles are so 'loose' that they engage just fine. Don't worry about it! But if your engine is ultra high compression and a bit sluggish to turn over from cold - you would probably be better off with the 9 tooth bendix.

[IslipMinor]

Our 1380 has a CR of around 10.7:1, but with a 60AH battery really does spin over very quickly from cold. I was very surprised at the difference the 10T pinion made to the cranking speed.

[mike.perry]

Job for tomorrow or whenever I get bored:- Count the teeth on my starter motors in the spares box