Morris 1275 clutch

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Garyjohndavies
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Morris 1275 clutch

Post by Garyjohndavies »

Hi am renovating a 1275 A plus engine which is fitted with a modified 1098 flywheel .
The starter dog is eating into the ring gear and wearing the collar at the back of the starter dog .
Need a measurement from the front of the engine back plate ,to the rear of the starter ring gear ,on a standard 1098 minor .I think my flywheel needs to be nearer the engine ?
Fitted new ring gear and will be fitting a new starter ,don’t want to butcher both !
All help appreciated .

Gary J Davies
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philthehill
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Re: Morris 1275 clutch

Post by philthehill »

I would suggest fitting a spacer on the starter shaft between the starter dog and the face of the starter. This would limit the travel of the starter dog but not imped the operation of the starter and interface between starter dog and the flywheel teeth. Trial and error will determine the depth of the spacer required.
I had a similar problem with my 1380cc but it was the other way round in that that the starter dog was too far away from the flywheel.
You will not get the flywheel nearer the block as that distance is fixed by the position of the rear face of the crankshaft.
Once you start modifying things these problems appear and have to be worked through.
Last edited by philthehill on Sun Aug 07, 2022 9:38 pm, edited 1 time in total.

StillGotMy1stCar
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Re: Morris 1275 clutch

Post by StillGotMy1stCar »

Just measured my 1098 at 39.9mm.
I wonder if this would be of use?
https://www.morrisminorspares.com/engin ... l-p1179153
Might be worth a phone call to ESM

Regards John
philthehill
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Re: Morris 1275 clutch

Post by philthehill »

The 1275cc ring gear in the link above is unsuitable for the modified 1098cc flywheel.
As I advised above and repeated in the Owen Burton Marina to Minor booklet - fitting a spacer on the starter shaft to limit the starter dog movement overcomes the problem.
Fouling of the flywheel by the starter dog was/is a recognised problem with some combinations of non standard parts.
Illustration below from the Owen Burton Marina to Minor booklet
Starter bendix foul.jpg
Starter bendix foul.jpg (852.49 KiB) Viewed 655 times
When removing the starter bendix make sure that you use the correct tool. The energy stored in the spring is enough to cause injury if the bendix is removed without care.

StillGotMy1stCar
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Re: Morris 1275 clutch

Post by StillGotMy1stCar »

Apologies Phil for putting a spanner in the works.
In the back of my mind the 1275 Midget ring gear is a slightly bigger internal diameter and you think is a good fit but after a few start up starts spinning on the flywheel.
However the one advertised by ESM gives the impression it fits the modified flywheel 10M001.
I have messaged them, I’ll let you know the response.
It would be nice to know if this is another option, as I will most likely fit a 1275 A+ to my pickup in the future.

Regards John
philthehill
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Re: Morris 1275 clutch

Post by philthehill »

John
The best option when fitting a 1275cc 'A' Plus engine to a Minor is to use the 1275cc Midget crankshaft, rods and flywheel.
The Midget crankshaft has a register and two dowels to locate the Midget flywheel. The flywheel ends up in the right place so no complications with the starter dog. You can machine and index drill the 1275cc flywheel to suit the 7.5" clutch cover.
My own 'A' Plus block is fitted with a modified 1275cc Midget crankshaft, rods and special steel flywheel to suit the 7.5" clutch.
I look forward to hearing what ESM say about the starter ring.
Phil

Garyjohndavies
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Re: Morris 1275 clutch

Post by Garyjohndavies »

Thanks one and all for your very good input .

Gary
StillGotMy1stCar
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Re: Morris 1275 clutch

Post by StillGotMy1stCar »

Thanks Phil, I totally agree with you regarding the Midget crankshaft etc, I’d be reluctant to pull my engine apart though as I believe it is a low mileage unit.
I was also lucky to find a misadvertised modified flywheel on eBay some years ago that was a bargain, but it also has the 1098 ring gear, which brings me back to the original post.
I’ve heard back from ESM and the ring gear in my link does fit the 1098 modified flywheel and gives extra clearance as seen in second image.

Regards John
philthehill
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Re: Morris 1275 clutch

Post by philthehill »

John
Many thanks for the reply.
I am not certain though that fitting the 1275cc Midget ring gear will give the required clearance.
The OP may still have to fit a spacer to the starter pinion shaft so as to position the starter dog just right when engaged with the flywheel as the OP has already fitted a modified 1098cc flywheel and still the starter dog fouls.
I have measured the thickness of a NOS genuine BMC/BL 1275cc Midget ring gear and it is 12.7mm thick (total). The OP gives the thickness as 12.45mm (tooth thickness) but that does not take into account the raised boss at 2.6mm thickness that the OP cannot measure as the ring gear is fitted and the boss is flush against the flywheel.
Taking into account the thickness of the raised boss @ 2.6mm and the teeth thickness @ 12.45mm the total being 15.05mm the ring gear teeth have already been pushed back towards the engine plate.
The ring gear cannot be moved out on the flywheel ring gear mount flange as the face of the flywheel is fixed especially as the flywheel is a modified standard BMC/BL item. Only if you have the flywheel especially made can the position of the ring gear be set to suit on the ring gear mount flange.
So if you fit the 1275cc Midget ring gear as supplied by ESM I cannot see any advantage to be gained because of the reasoning set out above.
Phil

StillGotMy1stCar
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Re: Morris 1275 clutch

Post by StillGotMy1stCar »

philthehill wrote: Thu Aug 11, 2022 9:57 am John
Many thanks for the reply.
I am not certain though that fitting the 1275cc Midget ring gear will give the required clearance.
The OP may still have to fit a spacer to the starter pinion shaft so as to position the starter dog just right when engaged with the flywheel as the OP has already fitted a modified 1098cc flywheel and still the starter dog fouls.
I have measured the thickness of a NOS genuine BMC/BL 1275cc Midget ring gear and it is 12.7mm thick (total). The OP gives the thickness as 12.45mm (tooth thickness) but that does not take into account the raised boss at 2.6mm thickness that the OP cannot measure as the ring gear is fitted and the boss is flush against the flywheel.
Taking into account the thickness of the raised boss @ 2.6mm and the teeth thickness @ 12.45mm the total being 15.05mm the ring gear teeth have already been pushed back towards the engine plate.
The ring gear cannot be moved out on the flywheel ring gear mount flange as the face of the flywheel is fixed especially as the flywheel is a modified standard BMC/BL item. Only if you have the flywheel especially made can the position of the ring gear be set to suit on the ring gear mount flange.
So if you fit the 1275cc Midget ring gear as supplied by ESM I cannot see any advantage to be gained because of the reasoning set out above.
Phil
Hello Phil, thank you for measuring your Midget ring gear.
The reason I mentioned the ESM Midget 1275 ring gear is because the OP has a standard 1098 ring gear fitted to his flywheel, the ESM modified flywheel has their10M001A 1275 Midget ring gear fitted.
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Ring gears.png
Ring gears.png (892.29 KiB) Viewed 500 times
Going by your measurements if theirs is the same, that will give an extra 2.6mm clearance.
That would leave 2mm to match my 1098 engine flywheel. There could be enough tolerance that a 2mm starter shaft spacer isn’t required, you would have to measure the starter being used.

My modified flywheel from an unknown source has a worn 1098 ring gear, so in my case I might fit the 1275 Midget ring gear and go from there.

This does clear one thing up for me though, because I thought the Midget starter ring fitted to the modified flywheel was to give clearance from the starter bendix when the engine is running, not to stop the damage when the starter is engaged, perhaps it’s a bit of both.

So I am glad Gary posted this question and it’s good to know about a simple solution with a spacer.

Regards John
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