Cush Drive....

[Flip]

..Sprocket Carrier bushes, or even in the words of Stein-Dinse, 'Ducati Tug Absorber Rubbers'.

Call them what you will but I need a little help please.

It's a job I've been putting off a bit if I am honest but with them being in there from new and now thirty odd thousand miles old I think it is about time I got on and changed them.

Now I know a couple of people here have expressed similar symptoms of a metallic sound when rocking the sprocket carrier back and forth but can anyone who has changed their bushes let me know if this sound is simply a result of the rubber bushes (item 18) hardening or if there was also wear on the bolt part (item 19) too?

https://www.stein-dinse.biz/eliste/index.php

[Chriswilly]

Had to change mine when I purchased 'Norah' which had been 'abused' by the last owner.

Bought the inserts from 'Baines Racing' in Silverstone - don't know what the brothers are up to these days (bicycles, it seems) but they have vast eperience of all Ducat marques.

Resonably easy once you remove the old units - may be good to change the male pins at the same time.

Good luck!

[Mr Gazza]

I was contemplating the very same about a year or so ago. I had the play that you mention on the sprocket along with the metallic clack at each end of the play.

I popped the wheel out to see what the damage was and found that the Coppaslip that I had applied to the pins had dried out and seemed to be working like grinding paste, as I have heard can happen, but never believed until I saw my pins.

I am changing all the Coppaslip for Moly-grease as I go along now, I washed and re-moly-greased the cush drive pins. Putting the carrier back into the bushes, in a randomly different position to before, I noticed that the free play was no longer there. So I tried it in all the possible positions and sure enough, there were tight and loose places. Maybe this indicates some lack of concentricity somewhere, or uneven wear, I don't know.
I simply installed it in the tightest position and have used it since with no worries...I'll probably inspect it during the current ongoing service.

[Flip]

Originally Posted by Mr Gazza

I was contemplating the very same about a year or so ago. I had the play that you mention on the sprocket along with the metallic clack at each end of the play.

I popped the wheel out to see what the damage was and found that the Coppaslip that I had applied to the pins had dried out and seemed to be working like grinding paste, as I have heard can happen, but never believed until I saw my pins.

I am changing all the Coppaslip for Moly-grease as I go along now, I washed and re-moly-greased the cush drive pins. Putting the carrier back into the bushes, in a randomly different position to before, I noticed that the free play was no longer there. So I tried it in all the possible positions and sure enough, there were tight and loose places. Maybe this indicates some lack of concentricity somewhere, or uneven wear, I don't know.
I simply installed it in the tightest position and have used it since with no worries...I'll probably inspect it during the current ongoing service.

Your findings are very interesting there Mr G- I didn't take note of it's position when I last removed it and I can't say for certain when I first noticed the metallic sound.

My main reason for changing the rubbers is simply that they must have hardened over twenty two years and so thought it a good idea.

I do think it is perhaps not quite such a good design as those more often seen on Japanese motorcycles as on the Ducati design although there is some cushioning there is still direct metal to metal contact which surely must wear to some degree?

[Mr Gazza]

It's not too bad a design really. The metal to metal contact is a weak point though. Hopefully a regular smear of Moly-grease will keep things going along sweetly.

I seem to recall sourcing Polyurethane bushes when I last though of this, but I think I remember the price being a little frightening.
Poly bushes would last a lifetime I would imagine, but still rely on the metal pin in a metal sleeve, so tricky to know what the answer is... Thankfully they do seem to have quite a long life anyway.

[Darren69]

I think you're right about the poly bushes. I thought they'd be a good idea too until I saw the price of them! Can't remember where I saw them but seem to remember they were red instead of black rubber.

[Luddite]

Originally Posted by Darren69

I think you're right about the poly bushes. I thought they'd be a good idea too until I saw the price of them! Can't remember where I saw them but seem to remember they were red instead of black rubber.

I remember!

From: http://www.ukmonster.co.uk/monster/s...ad.php?t=56456

Originally Posted by Luddite

Something like these, Mr Gazza?



https://www.ebay.co.uk/itm/New-Cush-...-/272984478887

Pricey mind you...

[Mr Gazza]

Thanks again Encyclopaedia Ludditica.
We seem to have reproduced the same thread from a year ago!

So looking at those bushes I so wish they would fit my bike.
Taking this a step further, if the holes in the single sider sprocket carrier are the same size as the holes in the earlier hub, then surely the bushes would bolt onto the sprocket and the assembly push into the empty bush holes?

I suppose it would be down to how easily the bushes slid in and out of the hub, as to whether you would leave the bushes pressed into the hub and remove the sprocket by undoing the nuts or just sliding the bushes out still on the sprocket.

Let's start the ball rolling... Who knows the diameter of the single sider bush holes and the bores for the silentblock type bushes in the earlier ones?

[Dukedesmo]

Originally Posted by Mr Gazza

Let's start the ball rolling... Who knows the diameter of the single sider bush holes and the bores for the silentblock type bushes in the earlier ones?

Monster cush drives; 35mm diameter, 24mm high, cush drive from SSSA (916); 38mm diam, 16mm high.

side by side view;

[Darkness]

So it would take a fairly large hammer to persuade them into place?

[Darren69]

Find out who makes them and see if they do some that will fit a Monster?

[Capo]

No hammer required for the SSA version

[Mr Gazza]

Originally Posted by Capo

No hammer required for the SSA version

I'm sure that Darkness was jokingly implying that the SSA bushes would need a big hammer to get them into the early wheel.. Obviously not a realistic idea.

I was pondering the idea of freezing the poly bushes with liquid Nitrogen and turning them down to fit the early wheel. This is a technique used by Oberon to produce a flat or concave face on an O-ring for their clutch slave seals apparently.

Maybe the polyurethane would cut okay without freezing? Maybe a sharp rotating disc cutter would work, like on a tyre lathe?

The lack of metal retaining ring on the poly bushes implies that there is an interference fit of some degree and the concave sides of the cylinder reinforce that idea, so it would be important to reproduce both those features when deciding on the size to reduce the bushes to.

I have no idea if super freezing would effect the bond of the bush to the steel bolt, nor what effect the freezing would have on working out what the final machined size would be.

Of course approaching this from the opposite direction, maybe the bush holes in the wheel could be enlarged. This would be rather permanent and if it didn't work it would be terminal!
Again I have no idea if there is enough meat on the wheel to do this safely, or how it could be machined... At least the holes would only have to be enlarged to a depth of 16mm to accommodate the poly bushes.

Any thoughts on the above anyone?

Probably simpler to try and find out if the correct poly bushes are available, as Darren suggests, but I would have thought that we would already know if they were made.

[Darkness]

It may be worth approaching Polybush or others to ask what they can do?

[damien666]

I’ve had poly ones on mine for a few years. Made by AFAM.