Author Topic: Primary case oil seal size  (Read 286 times)

Online Minto

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Primary case oil seal size
« on: 16.05. 2020 15:34 »
Hello all
I've had a good old trawl the archives here looking for an answer to this but not got a definitive answer. So, does anyone know what size the oil seal behind the clutch on a 52 plungie A10 is? The one held in place by the two riveted plates either side of the case.
I'd just order one off feked or somewhere but I have a Bearing Man up the road who are now open again, and it'll save me waiting days to get on with it. All the hanging round waiting for deliveries is cooking my swede. Suppose if I was more organised I'd have got everything ordered at the same time, but that's just not in my nature. Doh!
Cheers
Jase
52 A10 plunger
Aprilia RSVR

Offline Swarfcut

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Re: Primary case oil seal size
« Reply #1 on: 16.05. 2020 18:52 »
Jase. Nothing special about this seal, it's just a single lipped oilseal. The bearing supplier needs to know the shaft diameter, the size of the hole the seal fits into, and the required width of the backing carrier. From these dimensions an appropriate seal can be selected. Take imperial and metric measurements, BSA behaved a bit strangely at times. If a seal of the exact width (depth) required is no longer listed, a bit of creative spacer packing may be required to bridge a gap between the circular retaining plates and a thinner than standard seal.

 There is discussion on various ways to modify the seal mounting on the forum. Fixings range from bespoke bolted retainers, to Wilko and Oddpak rivets and old nails from your Dad's shed.

 Swarfy.

Online Minto

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Re: Primary case oil seal size
« Reply #2 on: 16.05. 2020 21:01 »
Cheers Swarfy
Already raided my dad in law's shed for some little nuts n bolts for the retainer plates... Might get a proper backing plate knocked up with some tapped holes in it, ready for the next time the clutch needs looking at.
Cheers
Jase
52 A10 plunger
Aprilia RSVR

Offline Russ

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Re: Primary case oil seal size
« Reply #3 on: 16.05. 2020 23:45 »
The seal supplied for mine, part # 67-1242 is marked{ P/N, 4250, 1902, KOK}.
O.D 11/8".  I.D 3/4". Width 1/4 "
1951 A10 Plunger.
Australia

Online Minto

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Re: Primary case oil seal size
« Reply #4 on: 17.05. 2020 02:02 »
Thanks Russ, that's brilliant. Would've just measured but won't get the chance to go near it just now but can pick up a seal on monday, hopefully.
52 A10 plunger
Aprilia RSVR

Offline morris

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Re: Primary case oil seal size
« Reply #5 on: 17.05. 2020 07:41 »
SKF CR20x35x7
'58 BSA A 10 SA
'52 BSA A 10 Plunger
'55 MORRIS ISIS
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Offline Swarfcut

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Re: Primary case oil seal size
« Reply #6 on: 17.05. 2020 09:12 »
  By my reckoning the mainshaft is actually 13/16" OD.  ( Pinion bush is ID 0.812/ 0.813" listed on BSA Service Sheet 702)

 Russ has a 3/4" seal, but this may be the nearest seal available from the supplier at the time. Morris' metric 20mm is also a bit tighter on the shaft, so both are slightly undersized. Is this how it's supposed to be?

 Any modern seal is better than what was the original offering, it appeared to be a resin impregnated fabric cup. No wonder they leaked.

 Have a look here for a choice of imperial seals.

https://www.bearingboys.co.uk/?catid=1319&display=&orderby=&att1=13%2F16inch&att2=&att3=&att4=


 Swarfy

Online Minto

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Re: Primary case oil seal size
« Reply #7 on: 17.05. 2020 10:10 »
Thanks folks, the seal that's in there at the moment appears to be made of some kind of hard, black cheese, with lumps missing out of it.
While reading other posts about this seal I started wondering about its purpose, is it to keep the bit of oil in the chain case or to keep gearbox oil or road crap etc from entering it?
I found quite a bit of oil had got into the clutch assembly, despite what seemed to be a reasonable gasket on the cover, there was also what seemed to be too much oil in the chain case, but the level screw being used was still the one two away from the tensioner (if that makes sense) I've done the recommended alteration now.
Cheers
Jase
52 A10 plunger
Aprilia RSVR

Offline Swarfcut

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Re: Primary case oil seal size
« Reply #8 on: 17.05. 2020 11:32 »
  Jase, The open, spring side of the seal faces the clutch, to keep oil in.  Some folks would use an extended Gearbox Sleeve Bush to completely enclose the mainshaft, bridging the gap and keeping any gearbox oil moving down the mainshaft and  thus depositing it into the chaincase in an effort to keep this area between box and chaincase a little less messy.

    Chaincase oil level is better set by draining off, then refilling slowly with the engine running, watching for oil to start flicking past the filler hole as the chain starts to dip into the oil. You just want a steady stream of  discrete drops, not a constant waterfall deluge. The oil only needs to come up to the lower  few teeth of the chainwheel, not halfway up the clutch!   Grease the chainwheel rollers on assembly, it helps anyway to keep them in place as you juggle it back together.

 Swarfy.

Online Minto

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Re: Primary case oil seal size
« Reply #9 on: 17.05. 2020 15:10 »
Cheers Swarfy
I'll owe you (and a number of others on here) a few beers by the end of this rebuild. Hopefully get to meet some of you in person sometime soonish.
Jase
52 A10 plunger
Aprilia RSVR