C: Clutch Comet Clutch Plate Spun in Basket

[tom wilson]

I have a Comet that has bonded clutch plates (Burman replacements) one of them has spun in the basket! Are these clutch plates slightly smaller or are the ears shorter, or has my clutch drum expanded? as the ears are only contacting 50% of the basket this a normal occurrence? for these new type plates, or just my luck!
Any suggestions to check or repair?

To help me obtain any parts needed do you know what other bikes have the same clutch fitted?

 

[Albervin]

I believe Panthers and Ariel Square Fours had similar.

 

[BigEd]

I have a Comet that has bonded clutch plates (Burman replacements) one of them has spun in the basket! Are these clutch plates slightly smaller or are the ears shorter, or has my clutch drum expanded? as the ears are only contacting 50% of the basket this a normal occurrence? for these new type plates, or just my luck!
Any suggestions to check or repair?

To help me obtain any parts needed do you know what other bikes have the same clutch fitted?

I don't have a Comet but have welded a strap around the outside of the basket of a Comet owner. I think this was to stop the basket spreading outwards. If your basket has expanded so that the inner diameter is now too large perhaps that might be why the plate has spun.

 

[vibrac]

The expanding drum scenario is indicated if its the first outermost friction plate that has spun the very outer one should be plain if my memory serves me correctly (for years I have had a Honda fitted to my chain comet and a Newby belt elsewhere)

 

[druridge]

Hi Tom

I dont have a Comet clutch handy, but suspect having another to measure up / compare is the easiest way forward.
There are a number of possibles that come to mind:
Why has only one clutch plate spun? Is that particular plate smaller(diameter) than the rest? If these are replacements for the 'original' plates, can you compare these? Has the drum been over-packed (too many plates)?
I'm used to the clutch on a slightly different Burman B52 box. On these, the plates are actually quite loose in the drum, that is sort of the point, allowing free movement.
Heavily used drums may have evidence of the edges of the clutch plate slots (dogs) having been filed smooth to remove notches / roughness to allow the plates to move forward and back freely. Quite a bit of this would be acceptable.
I do have more than 50% of the 'ears'(dogs) on my plates overlapping with the drum slots; but that wouldnt seem to be too much of a problem. The dogs aren't really 'deep' but somehow yours has got to a point with no overlap!
It seems unlikely that the inside of the drum would have been skimmed or machined in any way to improve things but its easily checked. There were actually 'earlier' and 'later' drums for Burman clutches, the plates are not interchangeable. I gather the slots were machined in the early drums, the later ones have short bars welded on to create the dogs. There were occasional problems with the early type of drum cracking at the back of the machined slots; this allows the sides of the drum to splay outwards - which could allow a plate to move?
Is the drum correct for the bike? There were Burman drums of various depth's to accommodate different numbers of plates.
Is the clutch centre actually dead centre within the drum? The Comet centre should have 5 studs, but these aren't always easy to find and 4 stud centres from different clutches (the 350 AJS/Matchless singles?) were sometimes adapted by having an extra hole drilled.
The inner face of the friction plates does not engage into the dogs on the clutch centre. This face should be free to rotate over the outer surface of the clutch ccntre; however, if there is an excessive gap then potentially a plate could be sitting so far off centre that the plates outer dogs could disengage?
Has the plate actually spun or just moved a bit / come out of its dogs?

Having just re-read my reply I'm not sure if I've helped or just asked a load of questions in reply to your question!
I'm intrigued, best of luck!

 

[tom wilson]

I don't have a Comet but have welded a strap around the outside of the basket of a Comet owner. I think this was to stop the basket spreading outwards. If your basket has expanded so that the inner diameter is now too large perhaps that might be why the plate has spun.

Hi Ed many thanks as it was the out side plate that had spun so you could be right, I shall try to measure it. But even at the gearbox end of the basket the plate ears are only just making contact

 

[tom wilson]

Hi Tom

I dont have a Comet clutch handy, but suspect having another to measure up / compare is the easiest way forward.
There are a number of possibles that come to mind:
Why has only one clutch plate spun? Is that particular plate smaller(diameter) than the rest? If these are replacements for the 'original' plates, can you compare these? Has the drum been over-packed (too many plates)?
I'm used to the clutch on a slightly different Burman B52 box. On these, the plates are actually quite loose in the drum, that is sort of the point, allowing free movement.
Heavily used drums may have evidence of the edges of the clutch plate slots (dogs) having been filed smooth to remove notches / roughness to allow the plates to move forward and back freely. Quite a bit of this would be acceptable.
I do have more than 50% of the 'ears'(dogs) on my plates overlapping with the drum slots; but that wouldnt seem to be too much of a problem. The dogs aren't really 'deep' but somehow yours has got to a point with no overlap!
It seems unlikely that the inside of the drum would have been skimmed or machined in any way to improve things but its easily checked. There were actually 'earlier' and 'later' drums for Burman clutches, the plates are not interchangeable. I gather the slots were machined in the early drums, the later ones have short bars welded on to create the dogs. There were occasional problems with the early type of drum cracking at the back of the machined slots; this allows the sides of the drum to splay outwards - which could allow a plate to move?
Is the drum correct for the bike? There were Burman drums of various depth's to accommodate different numbers of plates.
Is the clutch centre actually dead centre within the drum? The Comet centre should have 5 studs, but these aren't always easy to find and 4 stud centres from different clutches (the 350 AJS/Matchless singles?) were sometimes adapted by having an extra hole drilled.
The inner face of the friction plates does not engage into the dogs on the clutch centre. This face should be free to rotate over the outer surface of the clutch ccntre; however, if there is an excessive gap then potentially a plate could be sitting so far off centre that the plates outer dogs could disengage?
Has the plate actually spun or just moved a bit / come out of its dogs?

Having just re-read my reply I'm not sure if I've helped or just asked a load of questions in reply to your question!
I'm intrigued, best of luck!

Hi yes you sure have posed a lot of questions, The clutch looks to have the correct basket etc, with the latest bonded plates fitted, as it was the outside plate that has spun I would suspect that as has been suggested that the basket has now gone conical shaped (I shall try to measure it) but the one closest to the gear box the ears only just engage with the slots in a perfect world the ears should be longer. I will of course look at some of the other issues you have raised.....just in case many thanks

 

[nkt267]

I have a Comet that has bonded clutch plates (Burman replacements) one of them has spun in the basket! Are these clutch plates slightly smaller or are the ears shorter, or has my clutch drum expanded? as the ears are only contacting 50% of the basket this a normal occurrence? for these new type plates, or just my luck!
Any suggestions to check or repair?

To help me obtain any parts needed do you know what other bikes have the same clutch fitted?

I had this happen at the Manx GP in 2007.When I got home I found that there were cracks on every ear just at the bottom of the slots which allowed the ears to spread, about 35thou each ear.The cure on later Matchless/ajs machines was as BigEd says to weld a strap around the top of the ears just below the top. I picked up an excellent condition basket recently at a jumble for £15, just make sure that it's deep enough for 5 plates. The basket available from the VOCS is, if i remember correctly, the last incarnation of the Burman clutch with a solid basket with friction plates that have slots in them and not ears..John

 

[nkt267]

Hi yes you sure have posed a lot of questions, The clutch looks to have the correct basket etc, with the latest bonded plates fitted, as it was the outside plate that has spun I would suspect that as has been suggested that the basket has now gone conical shaped (I shall try to measure it) but the one closest to the gear box the ears only just engage with the slots in a perfect world the ears should be longer. I will of course look at some of the other issues you have raised.....just in case many thanks

If you need me to measure the basket for you let me know as it's not in a bike at the moment..John

 

[tom wilson]

I had this happen at the Manx GP in 2007.When I got home I found that there were cracks on every ear just at the bottom of the slots which allowed the ears to spread, about 35thou each ear.The cure on later Matchless/ajs machines was as BigEd says to weld a strap around the top of the ears just below the top. I picked up an excellent condition basket recently at a jumble for £15, just make sure that it's deep enough for 5 plates. The basket available from the VOCS is, if i remember correctly, the last incarnation of the Burman clutch with a solid basket with friction plates that have slots in them and not ears..John

Very interesting regarding the VOCS modified basket and plates I did not know about them, I will check out the cost (but times is hard.......can I blame Brexit? lol), many thanks