Author Topic: Plus clutch doesnt release  (Read 828 times)

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Offline ccmman

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Plus clutch doesnt release
« on: 26 Mar 2019 at 19:37 »
Dear DMF ers
I would like to introduce myself. I am Tom, a farmer in Leicestershire, and long time Duggie wannabe.
I recently took the plunge having sold my long-term Velo Viper, and bought Dick Bradleys very-nearly-finished Plus 80. It is fabulous, and I have got it running tonight, but the clutch will not release at all. I have adjusted it correctly, according to the manual, but it wont release at all, it is not dragging, just completely not releasing.

I was hoping post-war experts might be able to point me in the right direction.

Thanks.

Offline Clive

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Re: Plus clutch doesnt release
« Reply #1 on: 27 Mar 2019 at 01:10 »
it may be the friction plate has been put in the wrong way round [ longer boss to the rear] caught me out once on a mk 5 . i have never owned an 80 plus so the clutch may be different.
regards
clive

Offline eddie

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Re: Plus clutch doesnt release
« Reply #2 on: 27 Mar 2019 at 07:41 »
Hi Tom,
            Unlike the standard Mark series bikes, the Plus doesn't have a 'Ferodo' clutch plate - it has small round corks in an alloy plate. If the bike has been standing for some time, any dampness may have caused the corks to stick to the pressure plate and flywheel. I would suggest you adjust the clutch cable to remove any free play (to obtain maximum lift), then with the clutch pulled in, and the bike in top gear, rock the bike back and forth until the plate breaks free - then readjust the cable as normal.
  This, of course, assumes that Dick has fitted a 'Plus' plate, and not an ordinary Mark plate. The 'Plus' clutches can be notoriously fierce in their operation and various owners have tried different methods of 'calming them down' - the most successful seems to be refacing the plate with bonded on cork sheet.
  Hope some of this helps,
                                          Regards,
                                                         Eddie.

Offline ccmman

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Re: Plus clutch doesnt release
« Reply #3 on: 27 Mar 2019 at 09:38 »
Thank you very much for your replies, Clive and Eddie. If the plate is the wrong way round Clive, can I tell by peering in through the adjuster hole?

Eddie, I have tried rocking it back and forth. In fact, I took it for a ride in bottom gear, (I live in the middle of nowhere!) with the clutch lever pulled, rolling on on off the throttle, all to no avail.

Can I check/diagnose anything through the adjuster hole? I can see the mechanism working, but dont really know what Im looking at.

Sounds ripping on open pipes! V frustrated I cant get this clutch to release...

Thanks again.

Offline ccmman

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Re: Plus clutch doesnt release
« Reply #4 on: 27 Mar 2019 at 09:39 »
oops just re-read my first post...Plus 80.. :frown:..schoolboy error!

Offline eddie

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Re: Plus clutch doesnt release
« Reply #5 on: 27 Mar 2019 at 11:03 »
Hi Tom,
            About the only other thing you can check with the engine and gearbox assembled, is that the clutch is lifting 'square'. If you look into the inspection hole, to your RH side you can see the pressed steel spring plate. With the aid of an assistant, lift the clutch while turning the engine over on the kickstart - the pressed steel plate should run relatively true - if it is tipped, one side of the clutch plate is probably stuck, or you have one or more of the guide pin bushes (there are 6) dragging in the holes in the flywheel. Unfortunately, this will necessitate separation of the engine and gearbox and removal of the flywheel. Whilst the flywheel is off, check that the clutch springs are all of equal length.

  Regards,
                 Eddie.

Offline ccmman

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Re: Plus clutch doesnt release
« Reply #6 on: 28 Mar 2019 at 08:53 »
Thank you very much for your advice.
I will check back in with results!

Offline ccmman

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Re: Plus clutch doesnt release
« Reply #7 on: 01 Apr 2019 at 22:59 »
I removed the gearbox tonight, pleasantly surprised how easy it was thanks the the John Holmes manual.
ie leaving the engine in the frame.

I think I have found the problem. The driven clutch plate has been built with pop rivets, which have long heads..



Offline ccmman

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Re: Plus clutch doesnt release
« Reply #8 on: 01 Apr 2019 at 23:06 »
These seem to be pressing on the dished disk, (is it an oil slinger?) behind the drive dog, so pushing the clutch plate against the flywhel causing it to drag.

You can see the witness marks on the oil slinger. Hopefully if I just grind down the rivet heads, it should cure the problem..


Offline ccmman

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Re: Plus clutch doesnt release
« Reply #9 on: 01 Apr 2019 at 23:12 »
or do you think I should replace those rivets with something better?

Thanks, Tom.

Offline eddie

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Re: Plus clutch doesnt release
« Reply #10 on: 02 Apr 2019 at 07:29 »
Hi Tom,
             Yes, I would replace the rivets with solid iron rivets (as would have been fitted originally). It was not unknown for the centre boss to work loose on the original plates, so lighter duty rivets (pop rivets) will not be up to the job. On the original clutch plates, Mr Douglas used a bastard size rivet (something like .175" dia) - when the Club had repro parts made, they opened the rivet holes to a standard 3/16" dia - so drill out one of your pop rivets to check what you actually have. The original rivets had flat heads about 80 thou deep, and the shank of the rivet was just beaten down to form another 'flat head'. The rivets were inserted from the same side as your pop rivets. When I was involved with the Club's spares scheme, I test ran some of the clutch components in my Dragonfly - this involved turning up a set of the bastard size rivets from mild steel bar so that I could test just a new steel plate. When re-riveting the plate, make sure there are no burrs on the holes and that the plate and boss fit together neatly - then clench up opposite rivets in turn to minimise the chance of distorting the plate.

  Regards,
                 Eddie.

Offline eddie

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Re: Plus clutch doesnt release
« Reply #11 on: 02 Apr 2019 at 07:43 »
Tom,
        Having had a second look at the photo of your clutch - it looks if your bike is fitted with either a standard Mark type clutch plate (steel disc with 'Ferodo' linings) or a modified plate (steel with bonded-on cork lining). The original 'Plus' clutch plate would have had a 1/8" thick Dural plate with umpteen 3/8" dia cork inserts. It was these inserts that caused the 'Plus' clutches to be so fierce (too many leading edges to kick up as the plate started to bite!), resulting in owners trying various methods of calming it down! - the most popular (and reliable) seemed to be a steel plate with linings made from rings cut from cork tiles bonded on.  If you are lucky, you may be able to just undo the six nuts around the flywheel and remove just the pressure plate to enable the friction plate to be removed. The pins through the flywheel were often lightly peened to prevent the nuts coming undone - in which case, you may have to work through the inspection hole to remove one nut at a time from the other end of the pins (it's fiddly, but better than having to pull the flywheel off the taper). With the pressure plate and guide pins removed, don't attempt to turn the flywheel as this will result in the spring plate moving out of alignment (making re-assembly much more difficult). Note that the flywheel, pressure plate and spring plate have a reference line on their rims for re-assembly.

From the white line across the end of the crankshaft, it looks as if there may not be a split pin fitted to the crankshaft nut. Provided the nut is good and tight, don't worry about the split pin - it is better to fully tighten the nut and leave the split pin out, rather than back the nut off to accommodate the split pin - as this usually results in the flywheel working loose and ruining the taper!

  Eddie.
« Last Edit: 02 Apr 2019 at 08:06 by eddie »

Offline ccmman

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Re: Plus clutch doesnt release
« Reply #12 on: 02 Apr 2019 at 08:11 »
Thank you Eddie!!
I am about to go out and have another go, so your advice is well timed. Drilling out the exisiting rivets and replacing them, one at a time, would perhaps be a good method if there is no gap caused by the burrs you mention.
I will report back..

Offline eddie

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Re: Plus clutch doesnt release
« Reply #13 on: 02 Apr 2019 at 08:53 »
Tom,
         I didn't answer the question from your earlier posting - yes the dished disk is an oil thrower. In fact it is a double thrower - there is a smaller one on the inside that actually throws any escaping oil into an annular groove and returns it to the 'box via the front layshaft bearing - this oilway also serves as a breather for the gearbox. The dished plate that is visible just makes sure that any oil that does get out is directed away from the clutch plate. The only snag with this system is that if the gearbox is stood on it's bellhousing, all the oil will leak from around the input shaft!!!

Eddie.

Offline ccmman

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Re: Plus clutch doesnt release
« Reply #14 on: 02 Apr 2019 at 09:43 »
Eddie
yes it looks like it is Ferodo lined.
So I will try undoing the pins.

Offline ccmman

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Re: Plus clutch doesnt release
« Reply #15 on: 02 Apr 2019 at 20:39 »
I am glad to say that the clutch fettle went without a hitch!
My brother had exactly the right rivets in stock. Having drilled out the pop rivets, the holes turned out to be 3/16ths, and Mark had a bag of them, exactly the right length.
I do enjoy setting proper rivets, so that was fun. It is very easy putting the gearbox back in, and now the clutch works well.

Offline eddie

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Re: Plus clutch doesnt release
« Reply #16 on: 02 Apr 2019 at 21:03 »
Excellent news! I'm glad everything went to plan.

  Eddie.

Offline ccmman

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Re: Plus clutch doesnt release
« Reply #17 on: 03 Apr 2019 at 21:42 »
Thanks Eddie. It is always a relief to be able to find a solution to a problem, when at first you cant see whats wrong! if only this was always the case...

 

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