Author Topic: SRM gearbox sprocket nut  (Read 984 times)

Offline BSA500

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SRM gearbox sprocket nut
« on: 12.09. 2023 13:23 »
Hi,
 I have one of these nuts holding my sprocket on but the garter spring from the seal popped out. Can the seal be popped out from the nut and replaced? rather than having to replace the whole nut. I still have a horrible leak from the box when she is on the sidestand (mainstand lugs are broken) so anything to help keep the oil in helps. I will be taking the box out over winter to hopefully once and for all stop the leak so being able to replace the seal would help keep the costs down *smile*.
 I have replaced the bushes/sprocket main seal/main bearing is shielded type and the sprocket nut but the oil just pours out, it only stops when it needs topping up

1960 A7 (57 motor to SS spec)

Online berger

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Re: SRM gearbox sprocket nut
« Reply #1 on: 12.09. 2023 16:11 »
i found that oil crept out of the sprocket oil seal circlip groove so sealed it up with goo, the white stuff in the photo. i even tried a sealed bearing and took the seal out facing into the gearbox but when they are on the side stand it creeps out anywhere it can. now you have mentioned the nut with the seal i am trying to find mine for the berger build, i did find it AGAIN a few weeks ago but can't remember where it is so i will have to find it AGAIN! *bash* *pull hair out*

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Re: SRM gearbox sprocket nut
« Reply #2 on: 12.09. 2023 19:30 »
 *yeah* i found the nut that was in a safe place, if you find a bearing suppliers i bet they can find a seal to fit inside the nut, i doubt SRM would have one offs made or would they. *whistle*

Online JulianS

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Re: SRM gearbox sprocket nut
« Reply #3 on: 12.09. 2023 20:00 »
You should be able to identify the seal from the numbers moulded onto it.

Offline Rex

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Re: SRM gearbox sprocket nut
« Reply #4 on: 12.09. 2023 21:27 »
Or just measure it? It'll likely be in those new-fangled metric units but still do-able. OD, ID and thickness in the order.

Online chaterlea25

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Re: SRM gearbox sprocket nut
« Reply #5 on: 13.09. 2023 14:54 »
Hi All
Its a standard metric seal.
I apply sealant to the sprocket splines and under the lockwasher as well..
Leakage can also be from the layshaft bush if there is scoring in the alloy.
You need to be careful to ease the seal over the step on the mainshaft when fitting the nut..

John
1961 Super Rocket
1963 RGS (ongoing)

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Re: SRM gearbox sprocket nut
« Reply #6 on: 14.09. 2023 02:41 »
I followed John's advice when I rebuilt mine, sealant everywhere that it can be and with the SRM nut, no leaks! Tend not to use the side stand though....
Ian
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Re: SRM gearbox sprocket nut
« Reply #7 on: 14.09. 2023 10:19 »
The seal has the dimensions:

OD = 32 mm
ID  = 21 mm
thickness = 5 mm

Offline BSA500

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Re: SRM gearbox sprocket nut
« Reply #8 on: 14.09. 2023 13:14 »
thank you everyone for the replies. I will have the box out over winter and set it up on the bench and watch for where exactly it leaks from. Then start the task of sorting out the leak/s.
 I have to use the side stand for mine as the lugs for the main stand were worn away many years ago and broken. Somebody bodge welded a tube on for me but its not right. One day I will fix it.

1960 A7 (57 motor to SS spec)

Offline BSA500

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Re: SRM gearbox sprocket nut
« Reply #9 on: 08.03. 2024 20:20 »
For info you can get the seal for the SRM nut from lancashireseals.co.uk. 80 pence incl post it was 3.30 in total.

1960 A7 (57 motor to SS spec)