I am about to follow the instructions on various (old) forum posts, regarding adding an additional friction plate to a two friction plate clutch. I am doing this as I destroyed the splines on the centre of my 3 plate set up but seem to have a few sets of the 2 plate set up ....
I think I need to:
grind the "lip" off of the centre, level with the existing splines
Take an extra friction plate and remove the "tabs" on the outside
Add this extra friction plate to the back of the stack, such that it bears on the clutch basket.
Expect to mess with the clutch set up
Two questions about positioning and the clutch basket.
I assume the extra plate will self centre ? I ask this as I know ariel added friction material to the much later clutch baskets but it's rivetted on, i.e. they didn't use an extra plate
Do I need to do anything with the clutch basket beyond cleaning it up ?
I'll take some pictures and write it up and report back ..
I think what you describe is what I have done sucessfully in earlier years. The only thing I would suggest is to use a friction plate with a good amount of friction material remaining, and with the inserts still firmly located. Too thin a plate could risk it only partially locating on the clutch centre. Also check that the clutch drum runs reasonable true without much wobble, which is possible if there is wear on the chaimwheel centre and/or needle rollers.
TOWARDS A BETTER CLUTCH (I am not sure of the date of this as I cut it out from Cheval very many years back. John Mitchell
In a past issue of Cheval, Frank Wilkins wrote of the advantages gained by modifying the Burman clutch. This was the addition of extra linings on the back outer clutch drum such that one gets an extra rubbing surface plus the added bonus of a firm clutch. For those of you that missed Frank’s article I will repeat the theory.
The normal standard Burman clutch is very strong and robust and takes a lot of punishment. However, the inner and outer tongues or splines wear out as the years go by, with resultant clutch clatter on tickover, and on changeover from acceleration to deceleration. As the wear increases, the clatter not only becomes more pronounced, but the actual rate of wear will increase. Since Burman parts are now becoming somewhat thin on the ground, anything that can be done to reduce this is beneficial.
Burmans introduced on the very late export Huntmasters and Squares an additional lining surface into the clutch. This took the form of some Ferodo type friction material being riveted, or bonded, to the back of the outer clutch casing. These linings were of course bonded to the inside of this drum. Burmans then used a clutch centre drum (the mild steel splined centre carrying the plain clutch plates) with the spigot machined off the rear face. The removal of this spigot allows a plain clutch plate to slide freely on the clutch centre until it takes up a position, under pressure of the clutch springs, against the new linings in the back of the outer drum. Hence one new friction surface.
The added bonus is then achieved that the friction between the inner and outer drums thus created acts as a cushioning against back lash in the tongues and splines thus reducing wear and making a much finer assembly. I hope you are still with me at this stage. Now to the Manchester modification.
Select from your spare clutch plates one which still has a good set of inserts, but has bad wear on the outer tongues. File these off completely, leaving yourself with a toothless plate. Dismantle your clutch to the stage only of removing the plates, and the inner splined drum, ie, clutch centre. Carefully file (or machine) off the spigot at the inner end of the outer circumference, then reassemble onto the machine. Before assembling, clean up the back of the clutch outer drum, since this will effectively become a new plain clutch plate. Now place the modified clutch plate, with its inserts, into the outer drum so that it lies right at the back. Its outer diameter will be firmly held by the outer drum. Then place in a good plain plate, and insert plate, etc, in the normal manner. Finally, readjust the pushrod free play, which will in all probability alter during the initial bedding in to quite a large extent. Hey presto, a quiet clutch giving a bonus of two extra friction surfaces and reduced wear of the splines etc. Time required is only a couple of hours or so, and no special tools or the complication thereof.
Since the above procedure achieves an extra plate the thought occurs to me that a 350cc 2 plate clutch could be similarly successfully modified, giving a three plate clutch which would be quite adequate for a 500cc or 650.
Bob Brassington
Very interesting with regards to the wear. I mentioned in a post a few years ago that the clutch in my first 57VH had the ferodo ring rivetted to the outer hub, and the later inner hub without the lip was fitted, along with ferodo plates. The wear on that inner hub is negligible and it has done well over 100,000 miles so there is clearly something in the modification that reduces wear. Although I still cannot see how there is any cushioning effect with regard to the steel plates on the inner hub, which is where most of the spline wear takes place. So I will just have to accept it as the proof is my inner hub.
I have to admit to removing that hub a few years ago and fitting the earlier lipped hub along with cork plates and the lighter cork clutch springs as I love a light clutch but I can see the extra cork plate going in there now along with the unlipped inner hub.
David
It will work and stop the plates jingling at low speeds and low load. . ONE plate will be doing this so I'd use a new bonded one there rather than make the corks handle it.. Nev
Is it possible to use this method instead of riveting the inserts to the clutch basket on a Sq 4 , as I just had a bad experience , I got a new clutch basket, inserts and copper rivets from Club spares ,and took them and my old one for reference to a Harley shop , they said no problem as some old Harleys had riveted clutch inserts . When I went to collect them , he said there is some bad news , they had removed half an insert from the old basket to have a look at the rivet hole , the new basket had all the new inserts fractured and one broken in half , they had used an air powered riveter and at the rear of the basket the rivets were protruding an 1/8 of an inch ,i did get some good news though , they said there will be no charge . I now have a big list of where not to take your parts to .I am going to do- it- myself , I would like some advice on riveting or bonding the inserts to the drum , or is it OK to add an additional loose friction plate with no riveted inserts fitted to a Sq 4 .
As far as I'm aware, Dave, you can do this to any of the 'later' (post-war?) 4-stroke Ariel Burman clutches - it's a fairly well-known mod these days and I've never seen anyone say 'but don't do it to a Sq. 4'....
'55 Huntmaster, '56 VH, ' 51 VH, '62 Arrow, '80 R100RT, '00 Sprint ST (now with a new Arrow project, and just now those 4-stroke Ariel parts can't even make one running bike...)
daveleek wrote:Is it possible to use this method instead of riveting the inserts to the clutch basket on a Sq 4 ...
I am not sure the sq4 element is too relevant.
I guess the question is whether there is any difference between the "factory" approach of rivetting the friction material to the clutch basket OR the owner mod of adding a modified plate in there .... (although you can bet the factory wouldn't have done it, unless there was some benefit and it might be that rivetting on friction material was cheaper ??)
I'll report back when I've ridden my 350 with the recent mod.
At the moment, it's so stupid wet that it's not funny (look up Ross on Wye on the news ...)
