Author Topic: Fork oil seals 1950 T35.  (Read 5196 times)

0 Members and 1 Guest are viewing this topic.

Offline keith1101

  • Member
  • *
  • Join Date: Oct 2011
  • Posts: 15
  • Location: Oxfordshire UK
Fork oil seals 1950 T35.
« on: 11 Mar 2014 at 10:13 »
I am planning to replace the rubber oil seals and copper asbestos seal in the bottom cap.
Does the end cover cap for the link housing just unclip or screw off ?. If it unclips how best to do that.
I also read an article that I believe suggested using water proof pump grease when fitting the rubber seals.
Finally is there any hints or tips they may help me with the replacement of these seals and the C & A washer.
Thank you, Keith.

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1655
  • Location: Hampshire, UK
Re: Fork oil seals 1950 T35.
« Reply #1 on: 11 Mar 2014 at 12:53 »
Keith,
          The pressed steel covers on the leading link pivot have an 'O' ring in the rim and just have to be prised off. I say just prised off but they may be a bit stubborn as the old 'O' rings often become sticky and take a bit of moving. The 'water pump grease' dodge I use on the face seal for the actual link - new seals just need light lubrication to prevent them being shredded by the movement of a dry link - the water pump grease should only be necessary when trying to reuse old seals.
    The 'O' rings in the covers can be replaced without any other dismantling. To replace the face seals, you will have to remove the front wheel and leading link (along with the front mudguard on Mk4 & 5 machines). If you are a member, the LDMCC spares scheme should be able to supply the seals, copper/asbestos washers and the tab washer for the leading link pivot.
   When replacing the copper/asbestos washers in the bottom caps, do it with the bike standing on it's wheels - you will then be able to replace the cap without having to fight against the pressure of the spring. The caps have a very fine thread that can easily be damaged by fitting it cross threaded when pushing against the spring.

  Regards,
               Eddie.

Offline keith1101

  • Member
  • *
  • Join Date: Oct 2011
  • Posts: 15
  • Location: Oxfordshire UK
Re: Fork oil seals 1950 T35.
« Reply #2 on: 11 Mar 2014 at 15:03 »
Thanks Eddie, that is a great help, I feel more confident to get on and do it.
The seals are on their way from the club, but I did not purchase the tab washer.
My bike is a MK4, but fitted with MK3 forks and mudguard, the stronger option. I can not see a tap washer in the parts list.?
Regards Keith.

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1655
  • Location: Hampshire, UK
Re: Fork oil seals 1950 T35.
« Reply #3 on: 11 Mar 2014 at 15:24 »
Keith,
           It's item 20 on plate 24 in the parts book. (Part number 31506).

   Eddie.

Offline keith1101

  • Member
  • *
  • Join Date: Oct 2011
  • Posts: 15
  • Location: Oxfordshire UK
Re: Fork oil seals 1950 T35.
« Reply #4 on: 11 Mar 2014 at 15:49 »
Thanks, now on order.
Keith.

Offline keith1101

  • Member
  • *
  • Join Date: Oct 2011
  • Posts: 15
  • Location: Oxfordshire UK
Re: Fork oil seals 1950 T35.
« Reply #5 on: 16 Mar 2014 at 15:06 »
Eddie, thanks for your help. All done and oil tight.

Offline frankclock

  • Member
  • *
  • Join Date: Mar 2014
  • Posts: 9
  • Location: AUSTRALIA SOUTH COAST NSW
Re: Fork oil seals 1950 T35.
« Reply #6 on: 19 May 2014 at 04:36 »
Eddie
I have just purchased a mk4 & one of the upper seals are leaking
after reading you article on how to replace them you mentioned having the wheel on the ground as I had already taken the wheel  out      I removed a lower cap but it had no spring tension on it & I was able to replace it without any pressure stopping it
is this ok or is there something amiss
the bike has been restored & I have ridden it approx 120miles on my first run
secondly if I remove the link assy to replace the seals how do I stop the spring from going below the pivot hole
any help would be great before I start the repair
thanks
FRANK DEAN

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1655
  • Location: Hampshire, UK
Re: Fork oil seals 1950 T35.
« Reply #7 on: 19 May 2014 at 06:55 »
Frank,
          As you have little or no preload on the fork spring, I would think that either the spring has collapsed or broken, or has at some time been replaced with a nonstandard spring. There were 2 options with the original springs - both were wound from 5/16" square wire, were 10" long and 1" OD. with 25 turns. The 2nd option had the OD taper ground which resulted in a multi-rate spring. Now, Mr Douglas fitted these with the smaller diameter lowermost (which I think is wrong - multi-rate springs are normally fitted with the stronger end taking the shock load - to prevent the weaker end becoming coil bound - the usual cause of spring failure - which is not uncommon in the Mark series!).
  Getting back to your forks, I would suggest further dismantling to find the cause of this lack of preload. Having removed the end-cap from the pivot, and the leading link, you should be able to tap out the pivot pin - this will then allow the piston (and linkage) to drop out of the fork leg followed by the spring and possibly a seating ring/spacer (they usually stay lodged in the fork leg). If your springs do not match up with the dimensions above, you will need to find a replacement. Unfortunately, there doesn't seem to be any new springs available at the moment, so you will need to enquire within the 'Douglas Community' for a secondhand replacement. Reassembly of the forks is simply the reverse of the dismantling (without any need to make adjustments).
  Hope this is of some help,
  Regards,
              Eddie.

Offline David Lawrence

  • Senior Member
  • ***
  • Join Date: Sep 2011
  • Posts: 166
  • Location: Essex UK
Re: Fork oil seals 1950 T35.
« Reply #8 on: 19 May 2014 at 11:02 »
Hi Frank and Eddie,
Just a quickie, Club spares relatively recently had a batch of the parallel type fork springs manufactured, they still have a few in stock.
The cost at present is 70-00 a pair.
If you find you require new ones email the spares.
Good luck with your forks Frank.
Dave

Offline frankclock

  • Member
  • *
  • Join Date: Mar 2014
  • Posts: 9
  • Location: AUSTRALIA SOUTH COAST NSW
Re: Fork oil seals 1950 T35.
« Reply #9 on: 20 May 2014 at 10:52 »
Eddie & Dave thanks for your notes
just to be sure I am with you, when I took the bottom caps off I put my finger into the fork leg & could just feel something about 1 inch or so upwards
when I tried to lift the link arm up it was under a lot of tension thats why I was reluctant to take the link arm out not knowing how I would compress the spring on refitting the arm
looking at the parts list it seems it was the spindle p/n 31168 that I could feel
I rode 125 miles on my first ride & all appeared to work well
perhaps I should bite the bullet & strip the forks
Why do I buy bikes with odd? forks  my Scott OILEMATIC forks
I will give it a go
thanks again
FRANK

Offline David Lawrence

  • Senior Member
  • ***
  • Join Date: Sep 2011
  • Posts: 166
  • Location: Essex UK
Re: Fork oil seals 1950 T35.
« Reply #10 on: 20 May 2014 at 11:49 »
Hi Frank,
If you are going to bite the bullet I think you would find it most useful if you have a copy of the Douglas spares book to hand. All the componants are shown in exploded view and listed with their part numbers. If you do not have a copy The Douglas Club will willingly!! sell you a copy, also we have the manual in stock should you be interested. Both are direct copies of the original works publications, but I regret we cannot match the prices quoted.  :frown: :roll: :lol: They cost a very reasonable 9-00 sterling each plus of course the dreaded P&P.
If your want/need them please email me directly.
Dave

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1655
  • Location: Hampshire, UK
Re: Fork oil seals 1950 T35.
« Reply #11 on: 20 May 2014 at 12:44 »
Frank,
          With the bottom cap off the forks, the next component inside the leg is an alloy slider - this is blanked off about 1" from the bottom and has a large washer on a spigot that controls the damping (this is probably what you can feel). If the slider wont drop far enough to show at the bottom of the leg, it could be held back by burrs or damage at the bottom of the fork leg tube, or possibly by the internal linkage having been assembled incorrectly (one of the internal links has an eye that is offset from the centre line). If it is damage to the bottom of the tube, you will need to compress the spring enough to lift the slider clear of the damage in order to effect a repair. Probably the easiest way of doing this would be to wind about 3 turns of rope around the wheel spindle and the bottom fork yoke and wind it up like a Spanish windlass to raise the leading link. If incorrect assembly is the culprit, you will probably need to replace the end cap and then try to drive out the pivot shaft - this will probably still be under load from the spring, but the slider shouldn't drop far with the cap in place. Having got the pivot shaft out, you will then need to undo the cap again, but try to give it some support as you get down to the last few threads (so that they don't strip). You may then still have some trouble getting the slider out as the incorrectly assembled link may have bottomed out on the window in the back of the fork leg, resulting in a burr being thrown up.
   Good luck with the repairs,
                                           Eddie.