Author Topic: Another puzzle: plunger A10 drive side crankcase aperture, what size?  (Read 601 times)

Offline Steverat

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I have a spare crankcase for Josef's rebuild. Comparing it with the one off the bike, I see the drive side aperture is different.
Original case, datestamped 11/2/52 (AA7xxxx) is 46mm
Spare case, datestamped 26/5/52 (BA10xxxx) is 55mm

I attach photos.

My question - what is the aperture for, and why does it change? Is it right for the model and year - did BSA change the aperture in early 1952? Is it to accomodate an oil seal? But the AA7 case has an annular gap already, you can see in the picture. Parts list does not indicate any oil seal at all in this location.

1951 BSA A10 - now returned to Germany
1972 Triumph T100R Daytona
1924 B-S SS80
1965 Triumph SH Cub
1960 AJS M18CS

Online muskrat

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G'day Steve.
I wasn't sure what date they changed (thought it was 53) but yes the later plungers have the seal. The pop marks on the perimeter were to hold it in.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline duTch

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 I may be wrong but fairly sure the seal was introduced for '54 (as per parts list), but as the model runs start in (?) July/September (?) previous year some stamped '53 might have one......same as yours date stamped in May may mean they were getting ready for the run....My BA10 cases are stamped 23:12:52 and by the rest of the number, figure stamped about April '53- but I always called it a '52

 When I bought my lump it had an original 'shim' type oil slinger with a smaller aperture, but I changed it to take a seal, I just bought a seal that was the closest to doing the job and had the hole machined to suit.

  I just had that old seal at hand and depending how I hold my tongue, O.D measures to be 55.35-55.57mm, or in ye olde Englishe 1.1795-1.8275", which is maybe intended as 1.875"/ 1,3/16" (in even ye older ye English).... *conf*
 so may not be right, but gives an indication- I'm sure someone will have definite information.

 Hope that's some help

Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline Swarfcut

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 Perhaps this will help,   Early A7 Longstroke,  and all later A7 and A10 to about '53 have the small hole.  Later A7 and A10 have a bigger hole to accomodate an oilseal.

  The early engines don't have  a conventional seal. Instead they have an oil slinger, a thin spring steel washer which sits in its own little cavity, outboard of the bearing, inboard of the crankcase. In other words it goes into the case before the bearing outer. It rotates with the crank because it is clamped between the drive sleeve and the bearing inner race when the big nut on the crank is tightened.

 The cases were redesigned slightly in 1952/53. They gained the oilseal, lost the slinger. Also an oil feed to the camshaft from the relief valve, through internal drillings in the timing side crankcase. Early engines blow off into the oilpump cavity.

 The drive sleeves on all engines share the same dimensions but are not interchangeable. Later sleeves have a smooth periphery to run on the oilseal. The earlier sleeve has a spiral groove which acts as an Archimedian Screw to return oil to the crankcase, it will only work if it fits the hole closely and the spiral groove is clean and free from rust and other muck. So although they will fit, they will not work effectively unless fitted in the appropriate setting.

 The drive sleeves and cush drive  nuts from later Swinging Arm Engines are of a different design and not interchangeable.

  Swarfy.

Online Greybeard

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...Later A7 and A10 have a bigger hole to accomodate an oilseal.
As in my '55

Offline Swarfcut

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 Hi Steve. To add a little more personal comment to my previous post.


   If you are restoring for someone else there a certain decisions to be made concerning your time, your costs, hassle etc. Also the use the bike will be put to. A factory perfect rebuilt will cost a lot, look nice, and you will be scared to use it lest you dirty it, come off it or it gets nicked.  This may be what Josef wants, but it will cost. Sometimes it is better to build up a sound, working but not mechanically perfect or concours finished bike which can actually be used. Second hand used genuine parts and cheap paint is the way I would go if I were only doing local runs for leisure/ pleasure/ club runs. In other words get it a runner and get some fun. That paint run and a bit off rust are not seen at speeds of over 3MPH.

   Now back to your specific problems. No wonder you are confused. On your original engine there is a bit missing, namely the oil slinger,  part67-349, described in the parts book as a bearing shim. It is and it isn't. Yes it is a shim near a bearing, but it does not locate the bearing. It rotates with the crank.  Someone has removed the bearing at some time. There are two non standard holes drilled in your case, which hopefully  coincide with the outer race. You lucky man. A small punch will enable you to knock the bearing out, but never be tempted to do it cold. Warm the case in the oven, on the barbecue, over a camping stove, blow torch until the spit dances when you gob on it. The race may drop out. or knock it  out  squarely.  To replace put the bearing in the freezer overnight, heat the cases as before and it may just drop in or require a light knock with a hammer and a block of wood.

  The missing shim appears in other posts so you can find what you need.

  How badly damaged are the original cases? Looks that both sets need welding. If possible I would stick with the original cases.  Firstly it would be nice to keep the whole ensemble together,, and may be easier to register for road use. Secondly, you may already have the scroll type drive sleeve which will save you a little bit of cash. Thirdly, welding missing parts to castings will cost, repairing missing thread sides is a lot easier.  Find a local gearbox reconditioner, ask who repairs their alloy cases, or search for aluminium fabricators. These guys are usually pleased to do these jobs if you catch them right as it adds challenge and variety to their day. Suss them out first and be honest in what you need doing.  If they make it clear they will not help, fine, leave on good terms as they may be just having a bad day I pay them in cash if asked, bottles of beer if they don't.  Treat them right and they will do you a good job.

    Ain't that right Musky? 

   Keep on spannering,  Swarfy.

Offline duTch

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Quote
.........The earlier sleeve has a spiral groove which acts as an Archimedian Screw to return oil to the crankcase, it will only work if it fits the hole closely and the spiral groove is clean and free from rust and other muck. So although they will fit, they will not work effectively unless fitted in the appropriate setting..........

 and

 
Quote
......On your original engine there is a bit missing, namely the oil slinger,  part67-349, described in the parts book as a bearing shim. It is and it isn't. Yes it is a shim near a bearing, but it does not locate the bearing.......

 Yep- that's why I called it a " original 'shim' type oil slinger ", and I forgot about mine having the scroll...which is no more - *work*, and I believe the corresponding sleeve in the later models that run the seal has a slightly wider flange to be effective and maybe compensate for the 'slinger-shim' (I found one at a swappie and argued with someone who should know better who said it was for something else), although my modified one seems to work ok anyway, but don't recall how much the primary chain alignment was affected...

 With regard to welding, I was directed to a welding place at a local airfield who specializes in aviation welding, and did good stuff (conditions apply),which may be worth chasing up in your area


Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline Swarfcut

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  Thanks duTch, I may stand corrected on this one. While the overall dimensions of the drive flanges are the same  the seal type  smooth bit may be wider as you say. Without one to hand I cannot compare.  Came across this scroll type which someone has bollockska'd into a very effective crankshaft positioning device at the recent Copdock (Ipswich UK) bike show.  It has a raised ring to match the inner bearing race where the welds are. Should be able to restore back to almost as it was.

  Swarfy.

Offline trevinoz

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Re the scrolled sleeves, I don't think that they were fitted to all pre-seal engines.
I have several non scrolled sleeves but have only ever found one with a scroll which I took from a YA7 engine and have now fitted to a ZA7S engine.
The overwhelming majority of plunger engines I have found over the years have been ZA10 types and all have had no scroll.
The BA series is something of a rarity in Australia, maybe we got swinging arm machines instead. There seems to have been plenty of CA bikes here by the bits turning up.

Offline Steverat

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Thank you for the points Swarfy!

As an aside - Josef is indeed in pursuit of perfection, and I want the absolute best I can do for him.

The "originals" off the bike are AA7. So not really original. They also have some really unattractive damage of their own in the shape of a sawn out (by a loose clutch chainwheel) and welded up chaincase back.

Another set of BA10 cases is on its way down to me now from a kind gent in Scotland, I think they will be a lot better than the AA7s. I do have the other spare set with the front damage too, and I'm planning on resurrecting them by cannibalising the AA7s, cutting a piece of casting out to fit the hole, and fixing in with Lumiweld. Result hopefully 2 good sets, but a fair degree of certainty that I'll get at least one.

cheers
Steve

1951 BSA A10 - now returned to Germany
1972 Triumph T100R Daytona
1924 B-S SS80
1965 Triumph SH Cub
1960 AJS M18CS

Online Rex

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The earlier oil slinger design...obviously it must lose more oil to the primary than the later seal design or they wouldn't have changed it, but is the oil loss too high to be acceptable?
I don't want to draining the primary every hundred miles.. ;)

Incidentally is there a source for this component? Drags have none in stock.

Offline Swarfcut

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 Hi Rex.. The slinger  plate is a simple circular disc with slightly dished edge to clear the outer race of the drive side bearing. Easy to make from any thin sheet.  The later smooth oilseal type drive sleeve fits nicely in the hole and will work just as well as a bunged up scroll. In fact as other posts indicate there was a good chance that rather than waste time and money on a scroll, BSA just omitted this operation.  Your alternative is to modify the case to accept a seal. The later smooth drive sleeve seems to be available, sometimes incorrectly described as fitting all A7 and A10 motors. It is specific to plunger engines.
   The oil has to be pretty clever to get past the slinger, so don't worry about a flooded primary.

   Slinger part no 67-349  Described as a bearing shim in the parts book

   Scroll type sleeve  67-2053  Cush Drive Bearing in the book.

   Oil seal type sleeve  67-2071    Ditto

   Keep Spannering          Swarfy

Online Rex

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Sorry to resurrect this old thread, but having run the engine for maybe ten minutes in the workshop there's a definite drip of oil from the main bearing area/rear of the cush drive.
Has anyone ever checked how much oil spilling into the primary is considered to be normal or acceptable? At the rate it's escaping from the crankcases  I think it would become a problem in a few miles. This is a 1951 with the slinger arrangement.

If I have to strip the engine to sort this problem (if there is one) by machining the cases for a garter seal I'd rather do it now when the bike's in the workshop and spotlessly clean.

Offline Swarfcut

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  Rex... Assuming you have sourced  or made a slinger and it is in place between the bearing outer and the case, the drive sleeve should have minimal clearance to the hole, and ideally should have the scrolled edge, with a nice clean groove.  With the cover on, there will be less pressure difference between crankcase and primary, so under operating conditions the flow could be much less.

     In the good old days the primary cover was slapped on and that was that, no thought that the thing would leak. The primary case always dripped a bit, thanks to the narrow mating surfaces, thin paper gaskets and general heavy handed treatment. So the level stayed more or less the same.  They all smoked a bit, we just kept topping up the tank.  In these more enlightened times a proper seal is your best bet, or stick with what you have, see how it goes and relive a byegone style of maintenance.  Annoying, but at the time that was the way it was done.

 Swarfy.

Online Rex

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The drive sleeve is 43mm (yes I appreciate no-one should use metric measurements on a BSA!) and the crankcase 'ole is at 45.5 mm. Not a lot but enough it seems for oil to escape.
I hadn't considered the fixed volume aspect of the primary case being a factor, so maybe I will give the old girl some miles first and see how it goes.
Thanks Swarfy.