Author Topic: MkV Clutch  (Read 527 times)

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Offline TonyC

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MkV Clutch
« on: 08 Jul 2020 at 17:42 »
Hi all,

I have recently acquired a lovely MkV Douglas which had not been used for a couple of years. It started easily but after a short run the engine stalled and I had a lot of clutch smelling smoke coming from the clutch adjustment cover.
After some advice it was necessary to take the engine out to source the problem.
The gearbox side was dry, but the fibre clutch disc was badly contaminated, so this has gone off for relining.
After taking off the flywheel I could see that there was a little bit of oil in the base of the casting. After taking off the springs and looking at the thrust bearing I could see it was very dry and after taking it apart there was 5 ball bearings missing and a further 4 that were only half there size! Above the dust seal was an accumulation of metal fragments.
So I have taken off the cover to replace the oil seal and after removing the seal it turns out that it has been turned down to make it fit the 49 mm diameter, which being rubber does not work very well. I will be machining the cover out to fit the replacement 50 mm oil seal.
Hopefully this will cure the problem of the clutch burning so all I need to get now is some gasket paper to make one to to fit between the cover and the engine. Any recommendations on which thickness needs to be used?
Any other advice would be greatly appreciated

Cheers Tony

Offline isettaman

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Re: MkV Clutch
« Reply #1 on: 09 Jul 2020 at 08:36 »
Hi Tony
I stand to be corrected, but I don't think there should be a gasket on the joint between the engine and gearbox. After all, it's a dry cavity so nothing to seal.
Cheers
Dave

Offline TonyC

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Re: MkV Clutch
« Reply #2 on: 09 Jul 2020 at 08:54 »
Hi Dave,

Thanks for the reply, but it is the joint between the engine casing and the part that holds the oil seal in that I am questioning.
The gasket that is there is non existent and I have gasket paper that is about 0.5 mm thick so would that suffice?

Cheers Tony

Offline eddie

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Re: MkV Clutch
« Reply #3 on: 09 Jul 2020 at 11:32 »
Tony,
          There wasn't a gasket listed for the joint between the clutch spigot and the crankcase. If you are going to use a gasket, make it very thin - say .1mm - with a light smear of Red Hermetite.

   Regarding the clutch thrust bearing - the balls should be 7/32" dia, and you should have a 'full house' less one ball - this leaves enough clearance so that adjacent balls don't scuff against each other. When the flywheel/clutch is reassembled, you should still have about 6mm of free movement on the operating lever (in the bellhousing). Without this clearance, the thrust bearing will be continually under load, and likely to overheat - this may have been the cause of oil getting onto your clutch plate (past an overheated seal). If there is not enough clearance, check out the tufnol thrust pad in the spring plate - some bikes needed a shim behind the thrust pad - others didn't. Removing the shim may be necessary to gain the vital clearance. Also, the bronze bushes on the 6 studs through the flywheel should each have a thin spacer (about 1/16") to make the build height of the clutch assembly correct.

 Bear in mind that if you fit a gasket under the clutch spigot, that will also affect the clearance at the clutch thrust.

  Hope this helps,
                            Regards,
                                          Eddie.

Offline TonyC

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Re: MkV Clutch
« Reply #4 on: 09 Jul 2020 at 11:58 »
Hi Eddie,

Thanks for the reply.
Do you know what thickness the Tufnol thrust pad should be? Mine does look as though it has been cooked as well.

Cheers Tony

Offline TonyC

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Re: MkV Clutch
« Reply #5 on: 15 Jul 2020 at 20:34 »
Well the burning smell was from the thrust pad as the bearings were shot.
The thrust pad fitted on this clutch outer plate is a fibre material, not tufnol as Eddie has suggested using.
Which is the better option to replace it with as I have some tufnol I can use
Cheers Tony

« Last Edit: 16 Jul 2020 at 01:52 by Dave »

Offline eddie

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Re: MkV Clutch
« Reply #6 on: 16 Jul 2020 at 08:46 »
Tony,
         The original thrust pads were made of Tufnol (with a chamfer on the back edge to clear the radius on the pressed plate). It should be a plain washer (with the 4 rivet holes) - the 2 small cutouts in the centre of yours are not original! When you have the thrust race re-assembled, check that the thrust face is proud of the retaining plate that holds the assembly together (that is what has worn the groove in your thrust pad).

  Regards,
                 Eddie.

Offline tck

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Re: MkV Clutch
« Reply #7 on: 16 Jul 2020 at 14:27 »
I love that passing remark "after taking off the flywheel" 2 weeks in and I am still making a extractor that picks up on the 6 studs to take mine off!

Offline TonyC

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Re: MkV Clutch
« Reply #8 on: 16 Jul 2020 at 14:44 »
Well it did come off easy, so maybe I was lucky!

If you do use a full diameter of plate then it would be worth bracing it with some plates welded 90 degrees to it to give it a lot more strength and stop it flexing

Cheers Tony

Offline Jonathan Hewitt

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Re: MkV Clutch
« Reply #9 on: 16 Jul 2020 at 16:29 »
How near to Rugby are you ? I am sure I have a flywheel you could borrow.
Jonathan

Offline tck

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Re: MkV Clutch
« Reply #10 on: 16 Jul 2020 at 17:35 »
Thankyou Jonathan
That is very much appreciated and I will keep that in mind however I am a week into construction I have bought the circular blanks and the hex bar for central screw and the six sleeve nuts and since my method does not involve the difficult job of taking out the studs  (the nuts are extremely difficult to access)  I will press on and see if I am successful. Whatever the outcome I will give an account on my thread.
again that offer is most appreciated and I will keep it in mind

Offline TonyC

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Re: MkV Clutch
« Reply #11 on: 18 Jul 2020 at 11:17 »
Took out the phospor pins and set up in the lathe. Checked the thickness against the sizes on the drawing and as it was 0.6 mm thicker decided to a machine the fibre material that was on there. Also stepped it back by a 1/32" so it would clear the steel retaining ring.
Hopefully all ready to put back together.
Cheers Tony





Image orientation fixed - Dave, 19 July 2020
« Last Edit: 18 Jul 2020 at 18:51 by Dave »

Offline Dave

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Re: MkV Clutch
« Reply #12 on: 18 Jul 2020 at 18:52 »

Offline TonyC

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Re: MkV Clutch
« Reply #13 on: 19 Jul 2020 at 08:53 »
Oops, had read the post, just got to try and remember!
Cheers Tony