Hello All,
Upon reassembling the chaincase components, I find that the clutch sprocket is approximately 1/4” outboard of the Cush drive sprocket. Searching the knowledge base here, I found that there are shims available for the purpose of aligning the sprockets. However, I can’t find any reference or part # in the parts book. Any assistance in identifying and locating these shims would be greatly appreciated. Thanks in advance.

I'm very pleased to read this, as I just discovered a similar problem. I thought I'd fixed it a while ago but swapping various components without keeping records means it's back. Looking at parts diagrams there seem to be different thickness shims but like Barry I can't find out more than that.

Are there not different styles of hub for the cush drive? Ones not requiring spacer and those that do?

Mark

email (option): pes.sales@btconnect.com

BSAs had an engine sprocket cush drive. On Nortons it was in the clutch and on Enfields was it on the rear hub? I know it was on my '54 Bullet but don't know about the War bikes.

1/4" out? There must be something adrift here! The cush drive bearing #56 in this illustration either comes with the main bearing spacer as part of the unit or as a separate spacer ring #116 in the illustration. I think the latter is the earlier type and I have known guys to omit this ring and wonder why their engine wont turn over.

The sprocket alignment shims are #66-1707 (as required) and are only 32 thou thick. You would need an awful lot of those. I think that possibly the clutch is not fully home? Ron

email (option): ronpier@talk21.com

Firstly, thanks for the replies. The Cush drive bearing is of the later style with spacer as part of the unit. I took the clutch back apart to insure that nothing was getting hung up. The clutch sleeve is going on all the way and bottoming out on the shoulder of the transmission shaft. When the clutch sprocket and center are assembled without the roller bearings, the sprockets are in alignment. When the I assemble with the roller bearings, the clutch sprocket is out by 1/4” which makes sense since the bearings are 1/4” x 1/4”. I don’t understand how the sprockets could be this far out of alignment wit everything drawn up tight. Thanks in advance for any advice.
Barry

I estimate the difference on mine is about half of what Barry's illustration shows. Running a straight edge from the engine sprocket gives about 1/8 inch discrepancy.
Thanks as always Ron for the illustration.

You have the wrong cutch center / adapter
While they all look the same the te depth that the taper is machined into the center differs
and you have one designed for an alloy chain case
And just to make things more confusing most have the same part number .

OK, I'll go through this again...
The original BSA clutch adapter was a BSA part made to allow BSA to fit the superior Triumph clutch to swinging arm model BSAs after BSA bought Triumph in the mid 50's and they were able to get their hands on it...

This original BSA part enables the fitment of a Triumph clutch only to swinging arm BSA models (A7/A10, B31/B33)....Earlier boxes still in use retained their earlier clutches..If this original part is fitted to the earlier heavyweight BSA boxes such as the WD M20, the result is a misalignment as seen in the photos...The reason for that is that whilst the mainshaft taper angles are the same on both types of BSA gearbox the diameter of the tapers are different, with the S. Arm type being the smaller of the two...So, when you fit the original adapter to the earlier box it doesn't go as far onto the shaft due to the diameter dfference...

Long after BSA went bust and in response to the demand to fit earlier bikes with the Triumph clutch a couple of after market suppliers manufactured an adapter to the original spec. in every respect except for the larger diameter taper. That resulted in correct alignment when fitted to an earlier box....As a consequence, there is no revised BSA part number as it wasn't a BSA part...I believe L.F Harris use a '/A' addition to the original number (or similar) but I'm not sure on that...

Thus when purchasing a sleeve for use on an early box you MUST specify the application to be sure of getting the correct part...

However, all is not lost if you have the wrong part...Irrespective of whether you have a crankshaft sleeve with or without the 'built in' spacer it is simply a case of adding an additional spacer of the appropriate thickness (in either case) to restore correct alignment.. It is best to harden the spacer if possible but if that option is not available use something like EN16 material to make it...

The primary chaincase outer cover will still fit with the clutch etc. positioned a 1/4" further 'outboard'.....The method described was the normal 'dodge' employed before the new adapters were produced and I've done it many times..Ian

email (option): ian@wright52.plus.com

Kidderminster Motorcycles supplied me the Triumph clutch kit and correct adaptor for my M21

Thanks so much Ian for the detailed explanation. A couple of things came to mind last night that may have a bearing (no pun intended) on the situation. The bike is a 1944 WMD20 but according to the tappet cover, the engine is a 1953. This bike had not run for at least 20 years and maybe 30. When I originally took the outer chaincase off I found the Cush drive spring broken. I don’t know how often that happens but I’m guessing that running the bike this far out of alignment would put undue stress on everything.
I’m still unclear on the adapter in the sense that the sleeve and sprocket are bottomed out on the shoulder of the transmission shaft right up against the inner chaincase. I don’t see how it could go on any further. The spacer on the Cush drive seems like the simpler solution as sourcing parts from here in the States can be problematic. Would anyone have information on a source for either correct adapter, or spacer or dimensions for spacer? I’d have to ask a friend to make one as those skills are above my pay grade.
Thanks in advance,
Barry

Your '53 engine should have exactly the same crank shock absorber set up as a WD one (and it appears to)...The thickness of the spacer you need will be the same as the amount of misalignment you have..Usually, roughly 1/4" but you can measure it exactly off your own bike....
There are no spacers available as this was never a standard set up but a mofification to allow the use of the Triumph clutch, so you will need to find someone with a lathe to produce it if you don't have one yourself.......

Regarding your clutch adapter I can't really comment as I can't examine what parts you have but the misalignment issue does seem to lie there....
You can get the correct adapter from 'Montys Classic Motorcycles' in the UK...He is familiar with the various types but as noted previously you must describe the intended application when ordering....
As an aside, if the shock absorber spring you have fitted currently is an original BSA one it's the wrong one and unsuitable...The '4 lobe' shock absorber uses a spring wound from lighter, rectangular form spring wire...The round wire spring is much heavier in poundage and designed for the '2 lobe' shock absorber on later bikes...Ian

email (option): ian@wright52.plus.com

Thanks again Ian for your help on this. I undoubtedly have the wrong cush drive spring. Unfortunately, my parts book is 1949-1958 M models and I don't know if the part number is correct for the spring. It lists number 67-1136. Is this correct, and if not, could you please provide the correct number? Thanks much.
Barry

Barry the cush drive spring is #15-0046. But even now they are being made with round wire. It might be better to look for a decent second hand original on ebay, but get the seller to confirm that the free length is 2 1/4"-2 3/8"

Ron

email (option): ronpier@talk21.com

66-1136 is the round wire spring for the 2 lobe shock absorber, introduced in 1955...The spring number for WD M20s with a 4 lobe shock absorber is 15-46...You have to be careful with the illustrated parts lists and study them carefully as sometimes the number in the list is changed but not the illustration or there is more than one listing for a given part but only one illustration...I think the list you refer to shows a 2 lobe shock absorber cam but with a flat wire spring!!**(which wasn't done)....It can be very confusing on occassion..Fortunately in most cases everything is correct...Ian

email (option): ian@wright52.plus.com

Thanks Ron and Ian. I thought I had the wrong spring. Being a newbie on these bikes and not knowing that there's a mis match of parts is great to have a resource like this site and the generous sharing of knowledge. I did notice in my parts book that the clutch spring nut is drawn backwards. Luckily, nobody could install it that way.
Thanks again.
Barry

Here is a proper WD drawing. Ron

email (option): ronpier@talk21.com

I'm sorry but I seem to have got this all completely wrong...:upside_down_face: ....I thought we were talking about fitting a Triumph clutch...

Apart from the comments I made about the shock absorber springs and assembly which are correct, I think most of my comments were irrelevant if you are using a single spring M20 clutch and the standard clutch sleeve....It seems that the problem lies with the clutch, assuming you have the correct parts for the shock absorber (apart from the spring)....Ian

email (option): ian@wright52.plus.com

Thanks again Ron and Ian for walking me through this. I'm really scratching my head. All the parts look correct and the clutch sleeve, chainwheel, and clutch center all fit together as they should. The rear of the Chainwheel is very close to the inner chaincase so I don't see how it couldn't be seated against the shoulder of the transmission shaft. And yet, the chainwheel is outboard of the engine sprocket by about 3/8" upon more careful measurement. Everything appears to be original equipment. My parts book (again 1949-58)shows 66-1707, 66-1708 cush drive alignment washer and 65-2540 cush drive distance piece both of which don't appear to be there unless on the other side of the inner chaincase. If fabricating a spacer is the answer and it spaces out the engine sprocket, will the cush drive spring still fit? I ordered the correct one today.
Thanks for your time.
Barry

Did you say you had the crankshaft sleeve with the shoulder on the rear face 'built in'...If so what is the depth of that shoulder?....Can you post a picture of it?....Ian

email (option): ian@wright52.plus.com

Again, my parts book shows Cush drive distance piece but I don’t know if that is for a later bike.

It's what I spoke about earlier. Some have the spacer attached and some it's a separate part. I've no idea why or when it changed from one to the other?

But yours has the spacer which apart from a shim if needed, is all you should have. Ron

email (option): ronpier@talk21.com

Thanks Ron,
But as you said, the alignment shims are only .032" thick. I would need about 12 of them to align the front sprocket. Also, I'm wondering if I could compress the cush spring enough to get the nut on. Something seems amiss but I don't know what. The engine and transmission are set where they are and the clutch assembly seems to be set correctly on the shaft. What else is there? If the clutch sprocket can't go in any further, the cush sprocket has to come out, correct?
Thanks again for hanging in.
Barry

Barry does your clutch look parallel to your inner primary case? Could your frame or gearbox plates be bent or out of line? I don't know if it's possible the fit the three rear cotton reel spacers (8,9,10) in the wrong order and tip the plates over one way?? Ron

PS I calculate that if 8 and 10 were swapped round, it would move the rear of the engine plates over to the right by .15" (3.8mm)

email (option): ronpier@talk21.com

The gearbox mainshaft differs between the swinging arm and rigid/plunger models. At least I assume it does given that fitting a Triumph clutch needs two different adaptors. So could the problem lie at the gearbox?

I have two sleeves in front of me. One clearly needs a spacer.
The other is longer than the one Barry shows.
The difference between the two is 12.73mm

Mark

email (option): pes.sales@btconnect.com

The engine shock absorber assembly appears to be correct apart from the spring and no alteration or additional spacers should be needed there...The problem of fitting the nut will not be an issue when you have the correct spring which is a much lighter one...

The problem must therefore be at the clutch end...The first thing to do is to check that the frame parts are assembled correctly to determine the gearbox is in the right place...On the kickstart side you should have the longer of the two spacers fitted between the outer face of the gearbox plate and the frame...On the clutch side between the outer face of the gearbox plate and the frame you should have the shorter of the two spacers and the rear brake torque arm..Between the gearbox plates is a spacer that should be the same length as the width of the gearbox bosses.....With everything fitted and tightened the gearbox plates should not be under sideload and the gap between them should be approx. the same as the mounting lugs on the gearbox...

Once that is verified the next thing is the clutch and adapter...First determine that you have the right clutch adapter by referencing the correct illustrated parts list or by posting a picture of it on here...After that the clutch and its component parts can be checked....

Regarding the gearbox mainshaft all later boxes of the same type (later versions) use the same mainshaft and no other later mainshafts from swinging arm singles or plunger twin models will fit....I'm not as knowledgable when it comes to directly pre war models so the question of a wrong shaft from that period will have to be clarified by others on the forum that are more familiar with them..Alternatively, and more simply, you could just measure the length of the shaft from the outer end of the sleeve gear to the end of the shaft and submit that dimension here for scrutiny...Ian

email (option): ian@wright52.plus.com

Well gentlemen, we may be on to something. The spacer on the kickstart side measures 1 5/8” and the spacer on the clutch side measures 1 7/8. So, it appears that somewhere along the line, they were assembled incorrectly. I never disassembled this but merely had the frame sandblasted and painted. If this is incorrect, I will swap them and see if that brings the clutch sprocket more in alignment. I will check back with the results. Thanks.

I think the shorter one on the clutch side is 1.6" and the longer one is 1.75". Ron

email (option): ronpier@talk21.com

Thanks Ron. I’ll be able to get a better measurement once I get them out.

Changing the spacers picked up about half the discrepancy. The difference now is approximately 3/16". Would that put it in the range for using alignment washers? Now I would need about 6.

I'd still want to find out what is going wrong. Packing the cush out to correct some other problem is not right! Is the gearbox definitely straight in the frame. Have you checked that the frame is reasonably true? Do the wheels line up with a straight edge. Ron

email (option): ronpier@talk21.com

Is the rear brake torque arm fitted?...Also, when you place the straight edge across the clutch sprocket is the edge parallel to the face of the engine sprocket?....Ian

email (option): ian@wright52.plus.com

https://ibb.co/2hq3pT5

Thanks again Ron and Ian for working on this. I know it must be frustrating to try and troubleshoot something over the internet. I agree that shimming out the engine sprocket that far is treating the symptoms instead of the cause. Rear brake torque arm is on and I have aligned wheels with a straightedge. Don’t really know how to check the frame but the straightedge is parallel to the face of the engine sprocket.

Sorry, photo didn’t upload first try.

You state "The clutch sleeve is going on all the way and bottoming out on the shoulder of the transmission shaft".

It should not be bottoming out on the shoulder as this will prevent the taper from locking the shaft and adapter together. If you tighten the clutch nut and then remove the nut, is the clutch adapter stuck on the shaft or does it slide off with little effort?

From day one that photo appeared to show the clutch drum sitting too far out on the main shaft.
I usually do my trial assemblies without the chaincase on as it makes proper alignment much esier.
The two sprockets must be as close to perfectly in alignment as possible or you will grind the teeth off the drum sprocket in no time flat

BEcause BSA made all of their gearboxes apart from the plunger bolt on one all of the mainshafts are very similar and will usually fit into the boxes
The taper on all of them is the same but the clutch centers are different on order to move the clutch inboard or outboard .
Please do what Bruce suggested and also measure the distance from the back of the clutch basket to the chaincase .
Let us know what you find
It could also be the sleeve gear bushprotruding too far out of the end of the gear preventing the clutch centre locking on the taper .

Can I briefly put in a query about my own case?
I have 2 cush drive assemblies, one each of the types mentioned here.
Making the measurements as Barry has done in the above photo, the clutch sprocket is 1/16 inch proud. I'm wondering whether to take this up with a couple of standard spacers, or would it be better to get single spacers made to measure?
The cush drive is certainly positioned correctly, when I previously fitted the clutch it seemed right.

['Because BSA made all of their gearboxes apart from the plunger bolt on one all of the mainshafts are very similar and will usually fit into the boxes...']

Not correct I'm afraid...

The plunger A7/A10 bolt on box, the 4 speed C11G gearbox and the swinging arm gearbox are all of essentially the same basic (BSA) design with detail differences in mountings, gearsets, gearchange mechanisms etc...However, mainshafts from all three boxes are interchangeable...The swinging arm gearbox mainshaft has a taper and either the BSA six spring clutch or the Triumph clutch can be fitted with the appropriate adapter...The Plunger A7/A10 box has a spline so will accept the duplex chain plunger clutch...This shaft is also frequently used in the s.arm box as the spline is the same as a Norton and so there is the option of using the Norton clutch...(for Goldies etc. usually)
The C11G 4 speed box has its own shaft and its own clutch etc. and these aren't generally used in other models....
None of the above mainshafts shafts will fit a heavyweight box of the type fitted to a WDM20 , the post war models rigid/ plunger B Series and M Series or the 46/47 B31 ...
However, although the WD box and the later heavyweight types are visually different the mainshafts in these are identical and interchangeable as are nearly all internal parts....
Whilst the taper angle is the same in these boxes as swinging arm types/variants the taper diameter is different...Thus the problem when trying to fit a standard BSA clutch adapter for a Triumph clutch to a heavyweight box....
B31 gearboxes from 1946/7 have a shorter mainshaft of a different design and these are also not interchangheable with heavyweight boxes or the later s.arm boxes....The mainshaft is common to the B29 and WB30 box from which the lightweight B31 box was developed...So, due to the shorter mainshaft those boxes had a different version of the six spring clutch adapter with the taper moved within the adapter to align the clutch with the B29/B30 and B31 engines, which were wider than the pre war B Series engines that used the box originally...For that reason the six spring adapter from later swinging arm models and the swinging arm adapters for Triumph clutches are not suitable for these boxes...I had to make substantial alterations to an M20 clutch adapter and the clutch to fit a Triumph clutch to my WB30....Ian

email (option): ian@wright52.plus.com

Thanks everyone for helpful suggestions. Perhaps I used the wrong terminology when describing the clutch sleeve “bottoming” out on the shaft. I use a large socket and hammer to drive clutch center onto shaft so I know it can’t go on further and I have to use a puller to get the sleeve off the shaft. Distance from back of clutch sprocket to chaincase is 3/4” measured as shown. Thanks again for assistance.

A friend made up a shim for me and sprockets are now in alignment. Now just waiting for correct Cush spring and I can finish assembling the chaincase. Thanks everyone for the guidance and advice. This site is such a great resource.
Regards,
Barry

Hi

Just a few things to check down the road:
1. When you put the chaincase cover on make sure that nothing is in contact with that. I had an over deep pattern shock absorber nut which ground a nice circle in my chaincase. You might have a similar issue if the shock absorber is too far out. Equally it could all be ok if the underlying issue was the shock absorber. Just with checking
2. Is the spacer hardened? Trevor made an excellent point somewhere in a similar post, which is to use an old bearing inner cut and ground to the required width, that’s just easier than hardening and tempering mild steel. I think the spacer for the shock absorber should be hardened, but Ian would be better to advise on that.

email (option): dickie.bobbie@hotmail.co.uk

In an ideal world I'd recommend the spacer was hardened as they do wear, particularly so if the engine shock absorber isn't working correctly...Mark Cook makes the 'std.' thickness spacer to that specification...
If hardening facilities aren't available a material such as EN19 would make for a reasonably durable component..In other words avoid basic mild steels such as EN1A....Ian

email (option): ian@wright52.plus.com

Thanks again for all helpful replies. I definitely will check chain case clearance when I get the cush spring installed. Not sure if the shim was hardened. He used some shim stock that he had. He’s out of town this weekend but I’ll check with him when he returns. Thanks again.
Barry

As it seems there are three different thicknesses of these hubs, it might be more cost effective to make only one size and two spacers?

Mark

email (option): pes.sales@btconnect.com

Definately more cost effective considering the cost of cutting the splines and grinding the inner race region
However unless you want to ship them asa set , which wastes materials it will need to be well documented on the PES web page so purchasers can order the correct one .
As a person educated in the engineering sciences and a true conservationalist I hate wasting materials .