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Hi All, Anybody have any experience with converting normal rubbers to polyurethane version.
I’ve replaced lots of rubbers, but only installed the normal ones. They don’t last well.
I’m looking for long service life.
Thanks, Don


1973 Tiger 750
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Originally Posted by TR7RVMan
I’ve replaced lots of rubbers, but only installed the normal ones. They don’t last well.
I’m looking for long service life.


I always thought rubbers were a one time use thing but getting more service out of them is a novel idea laughing


Seriously, I too would be interested in the polyurethane replacements feedback as well.


Jon W.


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I had a friend fit some, they disintegrated into a sort of rubberised powder very quickly.


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'Cause there's bugger all down here on Earth'

An interesting point given recent events.

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Interesting.

I've been considering PU clutch rubbers as it seems the rubber ones go the path of all rubber products these days. That is they go to goo quickly in the presence of oil. I haven't found a source of ones that seem to be relatively oil resistant yet. Has anyone got advice on that?

Thanks for raising this TR7RVMan.

Cheers
Ray


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Hi, I've replaced 3 set of the normal black ones. They get soft & start oozing black goo after 5k miles & only 1.5 years. UK made & Taiwan made the same poor life. UK made had UK made molded in the rubber. Then I got new Cush hub assembly, stamped made in England. Same poor life exactly.

Indeed single use!

I'm fitting the urethane & see what happens.... I've learned when rubber goes soft on certain road conditions like about 30-35 mph cresting a rise, then backing off at top at curve, then just starting to accelerate out of curve I'll get a very sharp single or double clack. Very loud & startling. Wont' always do it, but some what repeatable. I'll let you know end of next year or.... Sooner??
Don


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Look forward to the outcome.
Ray


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I have found the rubbers to be highly variable, one's from Feked I threw away the day I got them. This was a couple of years ago, but there were little slits in the rubbers, that would be ideal starting points for disintegration.

I got my last patch from LP williams, nothing moulded on them, just plain, but they have held up well for about 5 years now. It was clearly a difference between them and the feked ones, dimensions slightly different, but also in the molding point nipples, etc.

I wonder if they are just a few bad Eggs out there giving them all a bad reputation?


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I've done both at various times on my Trident.....no real difference unfortunately.

One of the guys on TOL was buying extruded poly rod and making his own for a fraction of the cost.

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I have never heard the sound/ symptom that Don describes. I do get some noise sometimes at very slow speeds when turning into another road in second. I thought it was just the rear chain but that could be caused by the cush rubbers being worn. Mine have been in a long time and high miles.

Dave

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Hello Don; reading all these comments I am thinking that I had luck about that? As you know I put plenty of kilometers at constant strong speed and never hear any strange noise from that part.
When those rubbers need change? I mean, besides the obvious disintegration; that I never saw; by the way.
I remember to only service 2 of those hubs around 10 years ago. I changed the rubbers doing the long shaft method.
-In the 500 I have the shock absorber in the primary.

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I've bought some Tony Hayward poly cush drive pieces and fitted them to the clutch centre I'm using in my next project, but no experience of them yet. The claim is that they last longer. I hope so, because the rubber ones last no time at all.


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Hi, On the later cush hub there is 3 hex bolts in place of the 6 countersink screws.

Now this is interesting.... My friend John with '69 Bonnie just took primary cover off for another reason. Found all sorts of goo in primary. Took cush hub apart. Rubbers disintegrated.

Found the casting of "center" (what I'd call the drum where steel plates ride) fractured at the bore for spring cup! Looking like the spider was banging against it. John reported no odd noises. Felt normal. Rubbers were about 5-6 years old. Now shopping for new cush hub assembly.

I've not seen this fracture before. I've seen marks on spider where metal to metal contact took place but never a fracture. Looks like this piece is some sort of cast iron??
Don


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Hi Don, it would be great to see a pic of this fracture. Not heard of such a thing before. It could be a manufacturing freak, who knows?
Or maybe fatigue from undamped shocks?

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I've got a broken one too in my pile of bits. I've only got the big chunk left, no idea why I've kept it. Cast iron is quite a good bearing surface, maybe helps the clutch plates slide? At least until they get notched, as they do.

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Hi koan & Mick, I emailed photo. More to follow when I see parts in person tomorrow.
Don


1973 Tiger 750

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