Author Topic: 1954 A10 Clutch  (Read 798 times)

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RESTORER

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1954 A10 Clutch
« on: 23 May, 2021, 15:21:37 »
Hi All, I could do with some help on the clutch for my 1954 S/Arm Flash. It has the 6 spring clutch. I have searched and read the topic from rogereld on 23 Feb 2019. I have the same chainwheel wobble, but also a dragging clutch. When I kick over with the clutch disengaged the clutch spins freely, but when the engine is running the disengaged clutch still drags when in gear and changing gear is difficult. I have added new springs and have since bought new friction plates, yet to be fitted. I decided to take the whole thing off and investigate properly. I have two clutches, one that was on the bike and one I bought on a well known auction site. I fitted the bought one. My pics show the old one on the left in each case. The centres are lined up with the shoulders level to show the length difference, but also the two are very different.  Was the old one made like this or is it unbelievably worn?  The backplates also differ, with the old one having recesses to accept the sleeve. On the chainwheels (both 43T), there are also obvious differences but what is not so obvious is that the new Draganfly corks I fitted to the bought chainwheel are virtually flush with the chainwheel faces, do they swell up in time? The corks in the old chainwheel still protrude quite a lot, and heaven knows how old they are! The centre bosses also differ.  There are not any ID marks on any of the items so does anyone recognise any of them to be right or wrong for my particular machine. I believe this to be my last problem and hope to make the road this summer, Boris permitting. Thanks for reading and hope you are all well.
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1954 A10 Golden Flash, Swinging Arm

JulianS

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Re: 1954 A10 Clutch
« Reply #1 on: 23 May, 2021, 15:55:11 »
The clutch centres changed for the 1956 A7 A10 B31 and B33 when the fully enclosed rear chaincase became available.  The primary drive and chaincase were moved outwards by around 1/8 inch to allow the fitting of the front bit of the tin chaincase, otherwise there was insufficient space between it and the gearbox.

The changes were the introduction of the circular steel plate between primary case and crankcase, a new cutch centre (part 42 3107) to move the clutch out a bit and a revised cush drive to move the front sprocket out a bit to line up with the clutch. Pre 1956 and 1956 on parts dont mix.


RESTORER

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Re: 1954 A10 Clutch
« Reply #2 on: 23 May, 2021, 19:41:20 »
Hi Julian and thanks for the info. If what you say is correct then I should be looking to use the old parts to get the best alignment.   I will look at fitting a new cork insert into the old chainwheel, which should clean up well and looks to be of slightly thinner plate where the inserts fit.  Also, Draganfly list sleeve 42-3107 as the part running from 1954-59, so if this is not correct, do you happen to have a part number for the sleeve from 1954-56 for my machine, (engine no CA10-)?
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1954 A10 Golden Flash, Swinging Arm

Jim S

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Re: 1954 A10 Clutch
« Reply #3 on: 24 May, 2021, 01:39:27 »
Hi Restorer
I have found that clutch dragging and chainwheel wobble is caused by excessive run out on the face of the clutch backplate when installed.
With the correct clutch center installed on the gearbox shaft, install the backplate, bearing inner race, basket and nut (hand tight). With a dial gauge, measure the run out on the face of the backplate. I had one backplate giving in excess of 0.060in run out which was causing "drag" between the backplate and the chainwheel. In this case I replaced the backplate, but maybe it could have been salvaged by a machinist. Once you have a backplate with a reasonable run out ( 0.015in ?) You may improve it more by indexing the backplate on the clutch center to find the optimum position for minimum run out.

Concerning chainwheel corks, they can be made from wine corks and there are previous posts concerning how to make them. For sure they need to protrude beyond the faces of the chainwheel by about 0.060 in.

Jim


JulianS

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Re: 1954 A10 Clutch
« Reply #4 on: 24 May, 2021, 19:05:19 »
The 1954/55 clutch centre or sleeve as BSA called it is part 65 3873.

Bottom paragraph in below bulletin.
« Last Edit: 24 May, 2021, 19:11:44 by JulianS »

RESTORER

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Re: 1954 A10 Clutch
« Reply #5 on: 25 May, 2021, 20:33:34 »
Thanks for this new info lads, plenty to investigate. Julian can I just clarify one thing: you say from 1956  "introduction of the circular steel plate between primary case and crankcase". On first rebuild, looking at the D'fly 54-57 parts book, a circular plate was shown with no mention of the differing years so I fitted one, with a paper gasket on either side, thinking it had been left out when I bought the machine. I am now thinking that I might have made the situation worse and to correct the assembly I should remove the plate and just leave one paper gasket. This should show if I check sprocket/chainwheel alignment during assembly but I would appreciate your thoughts. The cush drive I hope is the original and OK, and the original clutch sleeve should be 65-3873 and also correct, although I do need a new one if I can find one. Otherwise, perhaps if I leave in the circular plate, I could use the 42-3107 but I will first try the correct assembly. Thanks again to both of you.
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1954 A10 Golden Flash, Swinging Arm

JulianS

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Re: 1954 A10 Clutch
« Reply #6 on: 25 May, 2021, 20:57:05 »
The steel plate 42 7518 was introduced on Parts Bulletin 4P dated November 1956 - "New parts for 1956"

I think you would find it useful to get the 1954-1955 parts book. The 1954-57 book lacks some detail for the earlier 1954-55.

Below is from that book, showing the clutch and primary case and the key.

RESTORER

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Re: 1954 A10 Clutch
« Reply #7 on: 26 May, 2021, 09:51:32 »
Thanks for this, and I will try and find a parts book. Another slight change I notice tucked away in this is a different distance collar, item 19. I guess 15-7563 must be longer than 42-4792. I don't have either but with my current set up, which includes the steel spacer plate, I can only fit a couple of washers between the back casing and the frame lug. I will let you know how I get on.
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1954 A10 Golden Flash, Swinging Arm

RESTORER

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Re: 1954 A10 Clutch
« Reply #8 on: 11 July, 2021, 14:55:40 »
Hi all, Having followed up on Julian and Jim's ideas, I am pleased to report that, after fitting new friction and driven plates I now have a working clutch. I have removed the spacer disc from behind the chaincase, rebuilt as far as Jim suggests and checked the back plate run-out. I don't have a DTI and mag base, but used an engineers steel rule with 64ths and have less than 1/32" of run out. However I still have the chainwheel wobble when the plates are not fitted, and I am beginning think that it is designed in. Please tell me if I am wrong! To illustrate I have attached an enlarged, partly coloured view of part of SS 308. When the clutch is fully assembled there is no wobble but when the clutch is disengaged, the chainwheel is free to float along the double ball race until it takes up the clearance to the back of the centre (blue-green). During riding, the primary chain will keep the chain wheel from straying when the clutch is disengaged. Has anybody got a section through the clutch assembly, similar to SS 308 but which includes the chaincase? Also does anybody have any dimensions for the clutch sleeves 42-3107 and 65-3873? I am not intending to make one but I now believe that with a 1954 model I should have 65-3873 but need to determine what I am using, so just the lengths would be enough.  Thanks again for reading.
« Last Edit: 11 July, 2021, 14:57:24 by RESTORER »
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1954 A10 Golden Flash, Swinging Arm

idie

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Re: 1954 A10 Clutch
« Reply #9 on: 11 July, 2021, 17:41:59 »
The BSA six spring clutches have an amazing amount of wobble when there are no plates fitted. Not much that can be done about it. Built in design. If you find it a worry then fitting a Triumph style four spring clutch will give you a better clutch. I have used the six spring type for years, so long as you don't use them on a tuned machine they work ok.

Jim S

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Re: 1954 A10 Clutch
« Reply #10 on: 12 July, 2021, 12:44:00 »
Hi Idle
I checked my notes from a previous clutch rebuild. After replacing a defective backplate, I had 0.019in run out on the backplate face, and by indexing I was able to get it down to 0.009in. You are measuring about 0.030in in your most recent build.

In your last post you say that you now have a functioning clutch but still have chainwheel wobble. Maybe the 0.030 backplate run out is contributing to that.

When adjusting the springs after the clutch is assembled, I disengage the clutch (tie wrap around the clutch hand lever), put a dial gauge on the outer face of the outside plate and use the kick start to rotate the clutch. I then adjust the springs to get minimum run out.

A dial gauge and magnetic base are a good investment imo. It was less than $50cdn on Amazon several years ago.

Anyway, if your clutch is working with no grinding when changing gears, that is great!

idie

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Re: 1954 A10 Clutch
« Reply #11 on: 12 July, 2021, 13:07:54 »
With no plates in the drum it can be moved a good 1/8th inch side to side as it slides across the two rows of balls. Once all plates are fitted it is then tight only moving when clutch is disengaged. Although I have a dial gauge I have always adjusted the plates by eye, watching how the plates lift and adjusting accordingly. Both my B33 and M33 don't give me a problem. I must admit that the Triumph style clutch as fitted to my Shooting Star is much easier to set up.

DAVE BRADY

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Re: 1954 A10 Clutch
« Reply #12 on: 12 July, 2021, 13:27:30 »
Hi,

Would this caged ball centre help?  This one from de Groot.  It should also be possible to fit a washer/spacer behind the centre to reduce the play.  Perhaps and A65 thrust washer could be adapted.  I am trying something similar with a thrust washer in an A65 clutch.

Dave.

DAVE BRADY

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Re: 1954 A10 Clutch
« Reply #13 on: 12 July, 2021, 20:07:30 »
Hi,

Forgot to include the image.
This from de Groot.

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Re: 1954 A10 Clutch
« Reply #14 on: 15 July, 2021, 09:37:37 »
Thanks Dave, I will go into that, but if by behind the centre you mean between the studded centre and the chainwheel, I don't think there would be sufficient  room for the tab washer to do its job at the end of the splines.
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1954 A10 Golden Flash, Swinging Arm