1974 450 MKIII clutch hub spring retaining post failure!

[LaceyDucati]

Bill,
As the pressure plate tangs wear and get "mushroomed", the sideways forces on the pillars will increase, so maybe worth looking at the pressure plate as well. I'm sure I can help out with a sketch of my modified pillars, it's a relatively easy job if you have a lathe or know someone else who has. Nova did make some replacement centres many years ago, however they copied the original design....hence the bodged Nova item on the left in the pic. I didn't attempt to repair that one properly as there were other issues with it. Another for the curiosity pile

Nigel

[themoudie]

Aye Nigel,

Thank you for your quick reply.

I have made a tidy dimensional sketch, with what I think are reasonable dimensions and will scan and post an image on this thread, and email a copy direct to you as well.

The spring cup holes on the pressure plate are certainly worn oval in some cases, so will need one of these plus other bits and pieces, so will contact you direct about these.

My regards, Bill

[themoudie]

Aye George and Graeme,

Thank you both for your time and generous offers to help me source replacement parts.

At present I am intending to see if I can modify the clutch hub, using the methodology outlined by Nigel in his email. I have made up a tidy sketch of the dimensions required for the replacement posts and will check them with Nigel.

As for the clutch case, I will see if a welded repair is possible. But, due to the force of the impact there has been a bending of the piece of the case that was punched out. Whether the fragment is used or the hole is filled with weld alone, the area will require machining to produce a flat surface on which a replacement access cover plate can be mounted. Please may I contact you Graeme via the PM service on the site, once I made some enquiries here?

Good health to you both, Bill

[graeme]

Yes

[themoudie]

Apologise for the delayed update to this thread. I have been riding the miscreant since repairing the clutch!

After Nigel kindly looked at my sketch drawing for a new spring retaining post/pillar and pointed out a lack of a couple of critical dimensions , I modified my sketch and then had some sets (6 per set) of pillars machined up.

I also had the clutch hub, with the 5 remaining posts attached, modified. The original pillars riveted heads were machined off in a lathe and then the posts were punched out from the back of the hub. The post holes in the hub were then opened up to 8mm ID and the hub and posts vapour blasted. The hub was then heated and the 6 posts dropped into place, their equidistance in the hub and being 90° to the machined surface at the back of the hub was checked. Then the posts were silver soldered into position. After cooling the whole assembly was then vapour blasted again and checked. All appeared to be well.

I re-assembled and adjusted the clutch, using a new pressure plate, pushrods/ball set, allen screw spring retainers, unobtainium spring cups found on 'Fleabay'. So far, after 2,000 miles I have not had any problems with sticking plates and clutch drag, but clutch slip can now be induced when opening up the throttle in 4th gear for an overtake! I suspect that either the fibre plates are coming to the end of their days and or that I have a warped 2mm steel plate, or two! A wee job for before the turn of the year.

I have attached images of the modified post/pillars and the refurbished hub.

Thank you to everybody who offered advice and to Nigel for his time and expertise in checking my sketch and our conversations regarding the modification.

Good health, Bill

[Duccout]

Hi Bill,

Looks like that should see the old girl out.


Cheers,

Colin

[themoudie]

Aye Colin,

Bit like a bottle of IronBru, made frae girders!

Good health, Bill

[DBDBrian]

Well done Bill, job sorted.

[Dave354]

Ouch! So glad that the incident wasn’t any worse and the rubber side stayed downwards!
I was about to mention stories of hub posts coming loose and many years ago Mick Walker advising to dot punch and spot weld. However Nigel’s advice is definitely prudent and his modification a very simple and elegant fix! When I rebuilt my 350 I noticed that the posts had all been braised over on the rear of the hub. I just hope they hold fast!
All the best for the rebuild and many more miles riding.

Regards

Dave

[themoudie]

Aye Brian and Dave, thank you for your compliments.

Dave
Just be aware of the comment that Nigel made earlier in the thread

Part of the problem beyond aging is attempts to secure loose pillars by welding or braising from my experience exacerbates the situation. I think the heat and uneven or rapid cooling causes embrittlement.

I don't wish to be a Jonah, but would keep an eye on the hub. Being a 350, it probably doesn't stress the posts as much as the 450, especially if you aren't racing the machine. But!

Good health, Bill