The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Gearbox, Clutch, Primary => Topic started by: Devlin on 22.07. 2022 22:17
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BSA A7 1949 plunger
Looking at the parts list and pictures there are two variations of assemblies and as I have no "old" parts to reference I am at a loss and given that I need everything that goes on the output shaft will I have a problem
Devlin
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Devlin The crankshaft splines and gearbox mainshaft remained the same from start to finish on rigid and plunger bikes. The drive sleeve for the early engine differs slightly from later models in that this engine has no crank oilseal and the sleeve has a larger diameter flange than the later version. 67 2053 is the part you want, and is fitted to all engines prior to 1953 model year, when the seal was introduced. From your earlier posts and pictures I assume these parts are correctly fitted as found. You just need a complete clutch and primary chain.
These are common to all years and models of rigid and plunger bikes. Clutch thrust washer which you already have 67 3276/7/8 comes in three different thicknesses to aid primary chain alignment.
When you say two variations of assemblies I reckon you are referring to the two versions of the so called 6 spring clutch. Single roller chain type used on Swing Arm bikes, and the duplex chain Rigid/Plunger type. The former will not fit, it's completely different.
ebay sellers lump the two as "BSA 6 Spring Clutch" hence the confusion for the unwary
My Parts Book 1954/1957 has the clutch you need illustrated on Page 24 "A Group Plunger Frame".
Plenty on the Forum about this primary drive, Plunger Models have had extensive coverage to date and posts and pictures also apply to rigid framed versions.
Swarfy
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Could you send me a link to your parts book, I have had a trawl through the appropriate section but I cant find it
Devlin
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Here's a link to our Forum Literature Section
https://www.a7a10.net/forum/doc/parts/A7_A10_1954_to_1957_Spares.pdf
This parts book also contains the later S/A models.
Swarfy
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Thanks again, Looks like I need everything from 8 to 23 , to begin with anyway,Rather than trawl the various suppliers shops ,if possible can you suggest a place that will have it all I have a feeling getting parts from various sources I run the risk of mismatching parts
Devlin
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Despite my best efforts I still connot source the correct parts, the pics show what I have got so far both claiming to be for ridged A7 another 2 attempts at other parts from ebay sellers never turned up although I see one up for sale again, I now doubt very much the knowledge of these sellers and suspect they are chancers I hope someone can throw some light on this
Devlin
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2nd pic - the clutch centre on the left is plunger type, the one on the right is from a BSA single or later A series with swing arm (gearbox separate from engine).
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Thanks, the one on the left is what I think is correct however, the spines do not engage, looks like a trip to the next normous event is on the cards, the biggest issue is the previous owner "lost" the box of parts he removed
D
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We can see who did their homework, eh, RD.
Side by side there is no mistaking the substantial centre of the rigid/plunger clutch, along with its splined boss. Looks the right part, a reasonable buy and should slide easily onto the gearbox mainshaft, so something not quite right.
Sell that other puny offering, it is the type found on S/A bikes, plus similar B and M ranges with the taper fit adaptor for the gearbox mainshaft. That pressed steel design comes in three different heights, to suit lower powered machines requiring less clutch plates. I made a dig at RGS owners finding an M series clutch under the primary cover..... That centre also suffers from loose spring mounts, so getting the clutch apart can be an entertainment.
Plunger chainwheel has a duplex chain, one size fits all from start to finish. All clutches suffer notching of the driving fingers, so obviously choose the best you can find. Only used on this chainwheel, note the threaded support bolts that fix the clutch cover, often missing or abused on used examples. Also look for a good track for the rollers.
Swarfy.
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It's going to be a challenge by the looks of it.
Thanks
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G'day Devlin.
Here you go https://tinyurl.com/yc53ew75 a good clean up and new friction plates, springs and cover.
Cheers
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Moving forward on the parts hunt, however bearing race 65-3912 is proving illusive, any ideas where I might find the diamensions of this as it looks well within the ability of a machine shop
Devlin
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Devlin, which race is this? Are you sure? That part number does not feature in any of the post 1949 plunger parts books I have. No wonder it's playing hard to get!
But...it is part of the S/A post 1954 6 Spring Clutch, which is not the clutch you want.
Swarfy.
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Its number 37 on the parts diagram on page 17 of the BSa parts manual number 15 looks like a bearing race but descibed as a retainer
D
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G'day Devlin.
I have the same results as Swarfy.
If it's the outer race that's in the basket, good luck. It's not listed as a replacement part. In the olde days you' just order a new basket!
Is it wobble with the basket your worried about? They all have a bit of that. The best I've been able to do is new rollers and thrust washer 67-3276.
I had thought about getting 1 thou oversize rollers and grinding the bearing race to suit. I don't have a spare to play with.
Cheers
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I am starting to think I have some sort of hybrid or franenstien bitsa, here is how it seems, I have a duplex crank sprocket which would suggest its a 6 spring set up, however the gearbox input shaft end is splined for 4 spring centre job, I sent for N0 40 and 62on the diagram part numbers 42 3107 and 42 3236 respectively to help me make sense of it all but they seem to be again for clutch centre 61 part 42 3220, is it possible the gearbox has been changed although I cant imagine it, I got the old duplex chain with the bike would a duplex chain actually work on a single clutch sprocket from a duplex crank hope someone can help
Devlin
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That shaft looks like a plunger/rigid shaft splined to take the plunger/rigid 6 spring clutch.
The part numbers you mention are both for the 6 spring swinging arm clutch.
Below is from the 1949-53 parts book showing the plunger/rigid clutch.
You can access all the A7/A10 parts books on this forum.
https://www.a7a10.net/forum/index.php?topic=12471.0
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Thanks, I can see where I was going wrong, looking at the wrong model years making sense now
Devlin
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Devlin This saga is going round in circles and cash is flying the wrong way.
Time for a reality check.
Julian has posted a couple of very helpful sources which will assist to put matters right. Look for Plunger Clutch. These models feature a bolted on gearbox with a slipper adjustment for the primary chain.
Your bike has a splined gearbox mainshaft, the clutch centre slides directly onto this shaft, abuts against that circular thrust washer, and is secured with a nut and tab washer. From your earlier posts you have already got this clutch centre. All the other parts you have bought are from the later model, the S/A versions with a taper on the gearbox mainshaft. None of them will fit. You need the clutch parts from the Rigid & Plunger framed bikes, all of which interchange from the 1946 Longstroke to the last ones in 1956.
You mentioned your plunger clutch centre did not fit, so a little more investigation is required, that gearbox shaft looks short, hope it is just the camera angle. Behind that thrust washer there should be two half round parts which make a support ring (67 3251) which fits in a machined groove on the shaft.
Swarfy.
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Thanks Swarfy, I cleaned up the centre and tried tapping it on without success, I will have time this week end to have a look at the situation, the shaft looks short as in that pic I think the washer is a bit down the shaft and I cannot remember any thing behind it,I have searched the part numbers from the linked parts manual from Julian with limited success but I have not had a real search as yet, worse case scenario is there another model year I can use or indeed any alternative complete set up I can use
D
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Devlin. I've just had a look back thro' all your posts and came across pictures of the primary drive posted by esteemed Forum Member Minto. These include a good pic of the gearbox mainshaft with the split collar/support ring in place along with views of the completely assembled clutch. I also found one of my own earlier posts detailing what looks to be an incorrectly assembled chain tensioner.
Splines on that shaft are 21mm long, from the threaded end to the end of the splines it's 34mm and I would expect around 40mm of shaft to protrude into the primary case. The shaft should have no end float and next to no up and down/fore & aft movement. In neutral it should turn silently. Clicks and ticks are likely to be the kicker return spring catching on the kickstart ratchet...an easy fix.
Just to confirm, does this engine have a single rocker box or two separate ones? Stick with the BSA Parts Catalogue 1949-1953 A MODELS Twin Cylinder to avoid confusion with later variants. Worth punting on a cheap reprint, I got mine from Ebay seller "Ekka's Mecca", a spiral bound offering with good quality print.
Swarfy
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Yes 2 rocker covers,
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I cant get the PM to Swarfy so hope you see this post instead PIC of Rocker coveer
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That cush drive looks all wrong - a 4 lobe sprocket with a 2 lobe cam?
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There you are folks, the elusive Longstroke in all it's glory. That looks fine to me, the cylinder head even has the two vertical fins adjacent to the spark plus.....not many of these fins survive.
Looks to have the later E3L dynamo poking thro' the front engine mount. What a find!!! Cush drive also looks to be the right one, correctly set up and relatively unmolested by the traditional use of the big hammer. In these enlightened times get the proper tool. Peugeot ball joint socket rumoured to fit....
Swarfy
Mod add: the tool https://tinyurl.com/yazushx5
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So far so good got the hub and chainwheel just plates, springs,cups and nuts to get however where does the 20 odd roller bearings go back of the chainwheel for sure but what acts as an inner race looking at the diagram I cant see what else is missing
Devlin
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G'day Devlin.
The rollers go between the chainwheel and center (hub). The bit that sticks out at the back of the center is the inner race and their held in by the thrust washer when it's all on the shaft.
I put the center in the chainwheel, insert the rollers, smear a bit of grease to hold'em in and offer it all up to the shaft.
Cheers
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I have a question re the spit collects,apparently they come as a one piece new and are spilt in two so does that mean they are cast not machined, there seems to be shortage of these and thought I could have them turned by a machinist but perhaps this would mean they would wear quite quickly, thoughts anyone
Devlin
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Should be no 'wear' as there's no movement. They need to be hard (because the lip they sit on is marginal) but not too brittle. Bit of heat treatment of appropriate material after turning up a ring and splitting into two perhaps.
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Does anyone have the dimensions of the collet ,long shot I am sure, I can get the inner diameter and thickness from the shaft but that's all ...unless
Devlin
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One space left but not enough for one more roller there is a bit n=more room if I shove them uo=p a bit but still cant get the last one in
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They are all in, it takes 18 rollers.
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One space left but not enough for one more roller there is a bit n=more room if I shove them uo=p a bit but still cant get the last one in
I have pondered this every time I work on the clutch 🤔
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G'day Devlin.
As Julian says their all in. Their designed to have room to move.
I pack them with grease, put the split collets on, mount the thrust washer then feed the clutch on. You will need to have the chain on the clutch and engine sprocket when feeding the clutch on. Use that third arm that all motorcycle mechanics have *smile*
Cheers
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This is standard practice. Headstock bearings are the same, almost room for another ball.
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Yeah, makes you wonder where they got the term 'crowded rollers' from when they're often anything but......... *smile*
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G'day Bon.
Crowded rollers means the rollers don't run in a cage like a normal ball/roller bearing. That way more rollers can be fitted in hence the term "crowded". So in respect the load is shared better. A normal caged bearing of that size would have only 14 rollers.
Cheers
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Finally got there via an add in OBM clutch now assembled, but I need a split link for the primary chain I will get a new chain eventually but short term a link will do, a google revealed very little, and the usual suspects again vague about year, part number and availability any ideas would be great