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Discussion Starter #1 (Edited)
Hi All, Regarding clutch rebound rubbers are T150 part # T4324 (57-4324) the exact same size as # 57-1723 rebound rubbers that would be fitted to twins?

Some sellers are selling them as the same, but were they? Or is the 57-4324 just slightly larger & firmer?

Thanks,
Don
 

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Don..I don't know but I'm not convinced any of the repop cush drive rubbers are the correct quality..
 

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I'm sure just about every owner would welcome an answer on this, it's a moot point. Many a rubber (excuse the pun) I've fitted has turned to mush in no time. Seems someone may be making these at home from god knows what as OME. A thought that did occur was why has no one got round to these in Viton type material, it's available in 50 to 80 shore, that must cover the OEM range, perhaps better.?
 

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Hi Don,

are T150 part # T4324 (57-4324) the exact same size as # 57-1723 rebound rubbers that would be fitted to twins?
57-4324 from a German seller:-



... unfortunately, I can't find a similarly-dimensioned picture of 57-1723 but, if you have any, you could measure?

Two things suggest they weren't originally the same:-

. the twins used 57-1723 (and 57-1722) before the first triples right up to the very last (twins);

. the very first triples' had higher cush rubber part numbers, succeeding triples had even higher part numbers (including T4324/57-4324); if 57-1723 had worked, why wouldn't Triumph or NVT have used them?

Also bear in mind 57-4324 rubbers aren't just "rebound" on a triple, they're the same on the 'other' ("Drive"?) side too.

Hth.

Regards,
 

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I have had a few sets and found some to need a lot of force to fit and others fit without much leverage at all. Very variable but all work OK. They tend to break up in 3 years, often just 3 rubbers of one shape of the 6 Obviously a different rubber mix by the maker at the time. I have a fairly hard set in at the moment and it works well. The next set is already fitted into a clutch centre ready to fit and are the softer rubber. I expect them to work just as well as any other.
 

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Discussion Starter #8
Hi Stuart, That's what I suspected. I got the larger ones from Rabers a few years ago as they said some guys think they work better. I tried to install them, but the fit was too tight. The main problem was too long on the long ways. I got the normal ones too so I'd have choices.

I now believe the stiffer large ones are Triple buffers. They measure 17.3x25.9mm measured like the illustration you sent.

The twin ones I just bought 57-1723 UK made measure 16.8x25.3mm long.

The new UK made I just got are the same as the ones I put in last time. Very easy to install.

When removing them they were not very mushy like the rubber was heavily deteriorated, but were soft. I could very easily remove with pocket screw driver & push back in with just fingers without compressing anything.

I can force the larger rebound in but it's a real fight & the rubber bulges so much as to possibly interfere with the side plate clamping tightly so that's not right. Too tight.

My thought is to grind the too large rubber shorter & maybe profile a bit closer to the 57-1723 UK made ones.

Or get the red set from Canada. Have grand kids over for a few days so not much time to work on bike. I'll try to fool around with bike some more tomorrow night.

Really I'm putting perfume on a pig as the spider & rear cover are worn out. I just kind of want to see what happens. I filed the grooving out of slots last time & they are grooved again in 7k miles so maybe they do wear faster after you file them. I need a complete clutch of course. Long term I want to try to get another 5-10k miles out of motor, then complete overhaul with low compression pistons, all bearings, guides etc. The winter of 2021.

Stuart, thanks again for the info. Another mystery solved.
Don
 

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Recalling the efficiency of the cam sprung arrangement on the rigid frame models, has anyone ever come up with a better substitute than the rubber cushions?
 

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Discussion Starter #10
Hi Freakmaster, Many of the Harleys had the spring cush hub on crank & worked very well. Maybe rubbers are lighter & cheaper??

Many bikes have the cush hub in rear wheel. Those use rubbers. I believe modern Bonnie has that. Lots of Japanese do also.

The rear hub cush works good, but the rubbers go bad there too.
Don
 

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Discussion Starter #11 (Edited)
Hi Stuart, Here's some photos of the 57-1723 UK made sitting on top of a Triple rubber. This gives a visual of what the difference is.

I decided to move forward by grinding rubber off the end of the triple making it same length as 57-1723. I ground the front side against spider down narrower at point to a degree, but left 2/3s of it chubby. This allowed proper assembly without over compressing rubber, but it's much firmer & a little thicker, so the effect is also compressing drive rubber a little more.

The cush hub still has good action, but is stiffer in both directions than when using all 6 UK made rubbers. I think this should work better. I hope to do 100 miles next week after I finish assembly. That will let me know. I'll report back.

The back corner & straight edges of rubbers are lined up perfectly. The triple rubber has a little different shape so it sticks out a little at the right side corner in photos. I didn't grind that. I only shortened the pointed end & part of the curved face.

Don
 

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Hi Freakmaster, Many of the Harleys had the spring cush hub on crank & worked very well. Maybe rubbers are lighter & cheaper??

Many bikes have the cush hub in rear wheel. Those use rubbers. I believe modern Bonnie has that. Lots of Japanese do also.

The rear hub cush works good, but the rubbers go bad there too.
Don
I have a 2001 Sportster...No actual cush drive, just the rubber final drive belt...My Ducati has a rear wheel cush drive like Japanese bikes. The rear wheel rubbers last a long time and are easy to replace..My double engine Triumph race bike has a 90's Suzuki cast rear wheel ,so I retained the cush drive to make the bike smoother ,LOL
 

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Hi Freakmaster, Many of the Harleys had the spring cush hub on crank & worked very well. Maybe rubbers are lighter & cheaper??

Many bikes have the cush hub in rear wheel. Those use rubbers. I believe modern Bonnie has that. Lots of Japanese do also.

The rear hub cush works good, but the rubbers go bad there too.
Don
The reason Triumph dropped the the sprung cam was to allow the fit of alternators in the early 50's, though I believe they did supply a few machines with cush cams later, such was the sentiment. I'm sure they changed to clutch rubbers reluctantly, but for sure it must have been a cheaper option. The fact remains, clutch cush (at least in Triumph form) is the poor relation, as you say capitalized on by others, and not particularly effective. Hence my question of alternatives.
 

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Once fitted, any style and type of rubbers i have fitted, as long as they go into the gaps, loose or tight just work. I could not notice any difference from one type to the other. The actual movement within the clutch centre must be very small anyway. I still have a clutch with no sticking and clicks into gear with hardly a noise using any rubbers i have at hand. Even mixing old ones with some new ones, i have never noticed any difference in operation.
 

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Hi Don,

The cush hub still has good action, but is stiffer in both directions than when using all 6 UK made rubbers. I think this should work better.
Hmmm ... this I'm dubious about ...

As you probably know, a given volume of rubber (natural or synthetic) can only deform, it cannot change volume. If you confine a piece of rubber on all sides, it's as hard as rock, because it can't deform.

When the cush drive's working, the inner and outer vanes move closer together, compressing either the 'rebound' or 'drive' rubbers until they've deformed to fill the spaces between the vanes when, because they're confined at the sides, they cannot deform any more.

If the triple triangular cush rubber is larger than the twin triangular cush rubber, if you fit a triple triangular cush rubber in the space on a twin, you've already deformed the rubber more than a correct twin triangular cush rubber; when the cush drive works, it won't have as much movement 'til there isn't any more space for the rubbers to deform into, when it'll lock up and not be able to absorb any more transmission shock. :( That you twin's cush drive "is stiffer" appears to be the logical manifestation of the foregoing?

Regards,
 

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Discussion Starter #16
Hi Stuart, You are 100% correct about rubber having to have a place to go.

I trial fitted the rubbers several times evaluating the "feel" when turning drum with my clutch holding tool made from old steel plate & a long handle. I fitted the rubbers to what I felt was a good compromise of compression of the softer drive rubbers & the ground down harder triple rubbers.

Had a chance to do only 20 miles today. The bike was noticeably smoother than prior. However as I had rather expected the clacking noise is still there. Changed, but there. Was not on known familiar route do to time constraints.

Wed. I'll do about 40 miles to fully heat soak on known roads & see if I can get a better diagnosis. The spider & rear cover of cush hub are very worn. But it that the source of noise? It sounds like noise is right from the clutch itself. Clutch works good.

Visual inspection showed no obvious problem other that the spider, hub wear. No marks on primary chain or case from chain rubbing. Measured chain again. Still only minor wear. Tightened tension one click (1/2 turn). No change.

Going into this I expected poor results so I got what I expected. No sure what I'll do next. I expect I'll get all new clutch parts, including all plates. Probably new chain too. I know the old clutch was junk.

It might be from trans, but what could cause that in trans? Main shaft feels good with no play & turns smoothly, Rear sprocket, no play & turns smoothly. Make noise in neutral or in gear with clutch pulled the same. About 3500 it's worse but does it at any rpm off idle. Quite cold, motor pulling, or compression braking. Free reving in any gear when passing from pull to compression brake it's noisy. Cruising at the point of overrun like a slight down hill, will rattle constantly.

I'll evaluate some more Wednesday & report back.

The alternator rotor feels tight on its center. I can't feel even a trace of play in crank drive side bearing.

I hate so say it, but the new clutch is a guess....

I'm open to suggestions.
Don
 

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Hi Don,

Have you assessed wear on the tangs of the plain plates? I have just fitted an Aerco 7 plate to my 77 T140. I changed the cush rubbers at the same time. When I had the cush hub apart, I found the back plate very worn by contact with the spider. So, I ended up changing the back plate. With everything apart, I noticed that the original plain plates seemed to have a great deal of free play in the grooves on the clutch center. The grooves in the clutch center are 6.5mm wide, I measured the tangs on the plain plate to be about 5mm wide. A look around on the web indicated that the plate tangs should be 6mm. I bought 6 Surflex plain plates to replace the originals. I liked the look of the Surflex plain plates, the corners of the tangs are rounded, and the inner corners are relieved to lessen the chances of binding.
With all back together, all is well. Big difference is that I no longer have a noticeable "ringing" noise that appeared to come from the transmission side. Riding the bike with a full face helmet, the engine noise is completely different. So, many new parts in the clutch and a change in noise. Whether this is due to the individual new components or the total effect I am not sure.

All the best,
Andy
 

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Ignoring the part number differences and Don's photo's for a minute, just a visual of the two hub housings would show you that the triple one is a larger diameter than the twin so would need longer rubbers.

BTW Norton Commando's have the cush drive in the hub, so its not just newer machines. Why Triumph never explored and adopted this as an option is another nail in the perpetual coffin. Rear hub cush drive rubbers are very easy to replace, 30 minutes max and you're done.
 

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It was mentioned that many Japanese and Europen bikes have a cush drive in the rear wheel on the drive side..On bikes with chains the cush drive is supported on both sides by ball bearings..
I have replaced quite a few rubbers in Triumph cush drives...The last one was my T140D and the rubbers appeared in bad shape. The "spider" seemed to be a sloppy fit in the housing,more so than other bikes, like it was worn.The bike rode and shifted like any other Triumph..I replaced the rubbers and did an engine overhaul....Afterwards the the driveline felt no better or worse than before, no noticable problems in performance.
This winter I'm going to try the urethane cush rubbers...
 

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Discussion Starter #20
Hi AndyT140, Thanks for your experiences. My basket & hub were grooved so I filed them a lot to get smooth. The tangs on steel plates were worn. I installed 7 new Hyde plates. I didn't notice a ring or other odd noise. However clutch didn't free perfectly all the time. Maybe had too much lift on pressure plate?? Hard to say. But the clutch was working quite good still even if not absolutely perfect. Other guys that rode the bike thought is was perfect, but not me.

I'll take a ride tomorrow & evaluate it with a clear mind set starting from square one. I'll take a dowel to listen to noises also. I'll take a note pad to record results as I find after so many road tests, I can get confused.

The loud clack was alarming. Even the least mechanical person that would hear it would say, what the heck was that & be started by it even with helmet & ear plugs.

The clattery rattle is not so loud. Can be heard with helmet on, but not so well with ear plugs & helmet. I usually wear ear plugs with my helmet.

The clatter I would swear is primary chain hitting case. However tension is between 3/8 & 1/2" measured with a tool I made from a dowel through oil filler hole. I can see no marks on alternator tube or engine case or primary cover. As you know 3 row chain extends into primary cover, while 2 row does not.

I will listen with assistant (John with '69 Bonnie) giving throttle. In neutral clutch out. In neutral clutch pulled. In gear clutch pulled.

In neutral the assembly is rotating. Clutch pulled, it may or may not be rotating depending on plate drag. In gear clutch pulled only the basket with its friction plates are rotating. So this might/should(?) eliminate the spider side play.

With side play in the spider I found it allows the entire inner hub to move outwards. Since the spider inner cover is the left side stop for basket, it has doubled or more the side play in basket... About to .038+". Will this excessive side play cause problems I don't know. Maybe part of clutch drag, but I don't know about the noise. Clutch drag is really very minor. Holding lever in 12-15 seconds the gears stop rotating I can tell by no clunk at all into gear & sometimes I need to let clutch out slightly to align dogs to get into first.

I will try to ascertain better where noise is coming from. I really expected all the noise to be from clutch rubbers. Now I'm thinking I might have other problems as well. I will spend $ as needed, but not throw parts at bike. I've found over the years a tear down with out a reasonable diagnosis is a crap shoot if you actually fixed problems.

Noise only happens when motor is warm/heat soaked. Hmm... rod knock? Main bearing knock? Oil light works properly looking at it. Doesn't come on heat soaked with idle at 8-900 rpm. If I clutch motor down to stall it slipping clutch oil light will wink on/off. I expect about 300 rpm ish. But of course oil light means nothing. Pressure could be 3# & turn light off. I have proper fittings for my timing cover & gauge. I'll check pressure hot heat soaked idle & reving. Then retest next morning to see what difference cold motor makes.

I've never personally heard main bearing or rod knock, in a Triumph, so I don't know if they sound like from timing cover or not. Again I could feel no play in drive side main bearing or trans bearings.

I have heard piston slap, but the noise seems too low. I have piston slap cold from near new. Cold it sounds like a tiny bell ringing. Warm is normal, no noise. Going down a long hill cooling cyl. it will sometimes sound like a loose valve adjuster. None of that has changed so far as I can tell, but I'll reevaluate it tomorrow.

Thanks again, Don
 
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