The BSA A7-A10 Forum
Bikes, Pictures, Stories & more => Wanted & For Sale => Topic started by: Devlin on 08.08. 2022 19:03
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BSA A7 1949
I need everything related to the clutch that slides onto the primary side crankshaft, plates, drum, springs, etc etc
adm edit: title edited. Please be specific.
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It all looks like the primary of my '55 Plunger. Can the experts confirm that? If so, the availability should be wider than stuff that's specific to the early model.
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G'day Devlin.
Again Draganfly are a good site for info and part #'s. https://tinyurl.com/2yt7dyxw
Only a few parts that are different for the early L/S compared to the later S/S plungers.
Cheers
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I'm also looking for my '47.
assuming that the '49 is the same, it looks to me that it's a basic 6 spring clutch like my early '50s Triumph and Matchless.
. . . except . . .
. . . for the twin row chain and the backing plate that everything stacks against. Plates, cups, springs and nuts all appear to be available on ebay. The backing plate is my issue. It holds 2 half circle rings in the transmission shaft groove and everything stacks against it. I believe I'll do a drawing for my local machine shop. The half circle rings are the tricky part. The covering 'dome' seems to be the same as my '40 M20 but I'm not planning to install it.
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That dome over the clutch helps to keep oil out of the clutch and it strengthens the clutch basket
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I'm also looking for my '47.
assuming that the '49 is the same, it looks to me that it's a basic 6 spring clutch like my early '50s Triumph and Matchless.
. . . except . . .
. . . for the twin row chain and the backing plate that everything stacks against. Plates, cups, springs and nuts all appear to be available on ebay. The backing plate is my issue. It holds 2 half circle rings in the transmission shaft groove and everything stacks against it. I believe I'll do a drawing for my local machine shop. The half circle rings are the tricky part. The covering 'dome' seems to be the same as my '40 M20 but I'm not planning to install it.
Hi Brandis - you can get the half-circle rings (collets) from Draganfly. I'm also looking for a thrust washer too..
Kind regards
Tom
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assuming that the '49 is the same, it looks to me that it's a basic 6 spring clutch like my early '50s Triumph and Matchless.
. . . except . . .
. . . for the twin row chain and the backing plate that everything stacks against. Plates, cups, springs and nuts all appear to be available on ebay.
Remember the 6 spring clutch on BSA singles and S/A A series is not only different from the rigid / plunger A series regarding basket and centre, but plates are different too - not only because of the different centre, but they differ in diameter by around 1/4" (the rigid / plunger is smaller).
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You folks just need to get the bits for "A10 Plunger Clutch". Same parts used from start with Rigid Longstroke A7 to Plunger A7/A10 finish. Do not confuse this clutch with the puny pressed steel centre later 6 Spring cursed device. RD is on the money with the plates, they are different sizewise. Availability of used parts is reasonable, new stuff genuine or repro also available. ebay is a good place to look. Duplex chain used is the same for all A models with Rigid or Plunger Frames.
Swarfy.
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Duplex chain is the same for all A models with Rigid and Plunger Frames.
What about the triplex ones fitted to export models? 😜
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Correct GB. Triplex Chain used on the Super Flash and also as an option to order says Roy Bacon's BSA Twins Restoration. My 49/53 Parts List includes the Super Flash supplement, but this carries no reference to the Primary Transmission. This list is also absent from my 54/57 catalogue. So your guess is as good as mine.
Swarfy.
Additional. The primary cover casting used is the same for all semi-unit bikes. Over time the position of the oil level cut out changed to reduce the oil capacity, so the part numbers differ. In practice any Plunger cover will fit any Rigid/Plunger crankcase. Later S/A primary cover is considerably longer, so easy to tell apart. Longstroke engines do not have the locating dowels fore and aft, a later improvement that keeps the narrow mating faces in line and aids an oil tight seal. Often damaged and discarded, these dowels are easy to replicate, and the same part is used on the timing and gearbox covers.
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Here is the BSA Parts Service Bulletin No.819 listing the triplex primary parts for the US for those of you that may be interested..