Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board Unit 650 clutch thrust washer

In the process of sprucing up the transmission on the '72 TR6 I wanted to look it all over, so I pulled the clutch and the gearsets. All looked good in the trans, except the spindle parts and detent spring. Th clutch was a different matter. I had replaced plates a couple of years ago, but never removed the basket or hub. When I did last week, the thrust washer was eaten alive. Most of it was ground up and gone, so I ordered one from MAP, who offered a "heavy duty" MAP replacement, which I chose.
This thrust washer is significantly thicker than the original, so much so that as I tightened the mainshaft nut, it locked the hub and basket together. Thinking I had made an assembly mistake, I took it all back out, reassembled and it happened again, so I removed it again, and compared the thrust washer to one from the '68 Bonnie I have disassembled on the other bench and it is much thicker. I put the washer from the '68 in the '72 and it worked.
Has anyone else experienced this? Is it possible there is more clearance in the earlier models or do I need to chuck this part and buy another for the '68 engine?

Thanks, Bernie

Mr. B -
Triumph experimented with several thrust washer designs through the 60's and early 70's that I'm aware of. However, I was not aware of any changes in thickness that might give you the effect you are seeing. Usually these washers are somewhat interchangeable.

Never the less, I think it's important to keep in mind that the clutch thrust washer, the 20 clutch basket rollers, and the infamous clutch basket wobble (or basket free-play) that everybody seems to be so worried about is only an issue for the fraction of a second that the clutch is disengaged. During the remainder of the time the engine is running, none of these are an issue since the whole unit turns as a solid lump while the clutch is engaged.

That being fact, the only way to wear out a clutch thrust washer would be one or more of the following...
- Use shoddy primary oil
- Use the incorrect volume of primary oil
- Not change you primary case oil regularly
- Hold in the clutch at stop lights instead of using neutral
- Using "heavy duty" clutch springs for street duty
- Plain old "old age"

Additionally, Sir Isaac Newton tells us that the clutch push rod and ball ramp would also exhibit similar wear, since they bear an "opposite, but equal force". Well, at least he tells me these things. :bigt:

Richard, Thanks for the reply. You may recall a few months ago I was trying to determine if indeed the bike was one with the shared crankcase/primary oil because I was continually finding the primary low on oil. I will have to assume this contributed to my thrust washer disintigration, and I'll keep a close eye on it from now on.
The clutch rod and ramp may also have suffered since recently I found myself with very little clutch action and had to make a fairly large adjustment to the adjuster in the pressure plate to return it to correct operation.
I'm in neutral at every stop, click it up just before full stop (I hate holding the clutch lever).

I guess I'll try the MAP "heavy duty" thrust washer in the '68 and if it locks the clutch, I'll chuck it and buy a stock one.

Thanks, Bernie (boy I miss you calling me Fish Breath...)

Bernie, there were two different thrust washers; both had the same O.D., but different I.D.s. If the large I.D. type was used on the wrong hub, the thrust washer would slip out of its groove and wear horribly.
The normal thickness of the washer should be ~.050".
'Heavy Duty' shouldn't mean thicker, but made of better material such as Ammco bronze.

Tom. my experience with after market "Bronze" heavy duty thrust washers is they get eaten up rather quickly. I have had both Bill's and Precision Machine's through here and have not been satisfied with either of them. The old copper plated steel ones still seem to be the ticket.

You are right about the id The 57-1735 (which is almost impossible to find in its original dimensions) - there are some made from the later 57-3931 washers, but these also fail pretty quickly as they are supported by the bent over tabs exclusively.

I have talked (and talked and talked and talked) to John Birch about this and have been trying to get him to make the 57-3931 with the 57-1735 smaller id. He has said he would look into it (look into it , look into it... ) On average I have come to believe it takes about 20 years to get small changes made in the UK. Especially if I could sell any... now if I don't need it, it comes right away, and keeps coming and coming and coming... I guess from back orders from 20 years ago.

Fish Breath -
It sounds as if your TS mainshaft nut has loosened off. Now you have a chance to check that ball ramp after all!

PS. I miss you too. :rolleyes:

:bigt:

Excellent thread gents, that went the printer and the the "good stuff" book. :bigt:

It's the same setup on BSA twins. I don't know how it will go in practice, but I don't like the way the whole clutch hangs from the end of the mainshaft, even with a small support bearing trying to steady the mainshaft just inside the oilseal in the sprocket cover plate, pushing on the primary chain still deflects the rear chain. What I'm planning is to make a new coverplate with a large ballrace 55X90X11mm with the normal shaft seal in the centre. Working with a machined plate and spigot(55mm OD) bolted to back of the clutch basket to support the basket directly onto the bearing in the inspection plate and so c/case, the bearing will then work to deal with thrust, and that thrust section on the centre hub will be cut down, though I plan to retain the rollers. I'm hopeing this will totaly stablise the basket and it can be shimmed to obtain a good clearance, unlike what often happens with a thrust washer where clutch lever travel is used up by excess play. Anyway that's the plan and I'll let you know how it goes.

T.Sharp, You may have hit the nail on the head, but impossible to check now since so much of the I.D. of the original thrust washer has been drained away in the old primary oil. Both the new one and the one I'm using from the '68 engine fit snug against the machined area of the inner, so I feel confident it is the right size.

RF, Are you refering to the nut that retains the kickstart gears? The tab washer was still intact when I took it apart, (I had the whole trans out for detent spring replacement and a general health check...)so I assume no backing off has occured. As for the ball ramp, I would like to have disassembled and renewed some stuff in there, but those $%%$#%# common screws they use to attach to the outer cover were put in last by King Kong.(Slots are in poor condition to say the least) I'm not afraid of much in bikes that aren't going anywhere soon, but this one is going to the 3 state, and I dont relish the thought of breaking a screw off in the cover, since the ball ramp seems quite fucntional. I'll look it over when the '68 engine is built and the rather scruffy looking outer trans cover from it looks presentable enough to substitute for it if necessary.
(Boy it's nice to have a nearly complete set of spares in the garage...)

Thanks, Bernie

"it can be shimmed to obtain a good clearance, unlike what often happens with a thrust washer where clutch lever travel is used up by excess play. Anyway that's the plan and I'll let you know how it goes."

Am I missing something... this is a Triumph clutch?

Yep, I know its a Triumph clutch John what I'm talking about is a major mod to an A65 clutch but its probably applicable to a Triumph twin clutch which is similar and it would mount the basket to the inside wall of the chaincase and make the thrust washer set up redundant. I'm just in the process of drawing it and will find out if it works.

Mark: Then we must be talking about another washer, one that I have never seen. The thrust washer (57-1735 and 57-3931) used in a Triumph (also BSA) clutch has nothing to do with clutch lever travel.

I understand supporting the mainshaft with a bearing in the clutch door, something that has been done and offered commercially for 30 odd years, but the thrust washer I mentioned above hasn't anything to do with clutch lever, or its related parts - cable, 3 ball lifting mechanism (A65 lifting arm), clutch rod and adjuster.

So which washer are we talking about?

OK, I was hoping somebody else would ask. Which way does the copper side of the washer face? Years ago when I replaced mine, the old one was so worn I couldn't tell which way the new one was supposed to go, and off hand I can't remember how I put it in. I have a new one now, and as I'm going in soon to replace the primary chain and tensioner, I'll be in a good position to change the washer too.

The washer police do not have this on their hot sheet, but the copper plated side goes against the clutch basket.

John At one time I was having difficulty with the clutch sticking, dragging and not fully releasing and I noticed that the first part of the lever travel was not very effective because the basket was moving out with the rest of the clutch, when if it stayed where it was would have been better. A thicker thrust washer would have put the basket closer to the hub and if the basket is out further so is the entire clutch pack even though the hub stays in the same spot, then all the lift would be used seperating the plates after the pushrod was re-adjusted. I think my thinking is ok, anyway some of those narrower plates which didn't stick together fixed it.

I find a lot of these posts interesting with their talk of 'non standard parts'. I've been using a UK company who have been Triumph dealers since 1938 (!), and everything they've provided for my '69 Bonnie have been spot on. If you're interested, Google 'Wilemans Motors'. I'm not trying to promote them, but they flog good stuff (if you're fed upwith inferior products)!

Since oldbeefer has revived this post I thought I would give 'the rest of the story'.

I used the aforementioned thicker thrust washer in the '68 clutch and it worked a treat. Something is different between the '72 and the '68 that doesn't come easily to my eye.

Bernie

Not sure if I'm really going to help here. But I'll chime in anyway.

I replaced clutch parts on by 68 T120 a couple of years ago. Needed new thrust washer and the hub (57-1734?) was worn. The helpful guy at my local Brit shop said use a later setup - I guess T140?? In this set the thrust washer I.D. matches the rebate diameter on the hub and can't flog around. He said they need to be used as a pair but can be retro-fitted. (Assume this also works for BSA A65s). Unfortunately, when I recently wanted to do this for my A65 that very helpful gent had left the employ of my local Brit shop (their loss!!) and I couldnt get the details again. Newbie customer service dude didnt have a clue what I was talking about, so I got set up with a one of the 'old style' thrust washers that has about a 1/4" larger I.D. than where it sits on the hub which (I was told by the you beaut service guy) promotes wear of the thrust washer as it flogs around. It looks to me like the 'folded tab' modification to stop the thrust washer flogging about doesnt work because in the box of dead clutch bits that I got along with a stack of BSA/Tri parts there is a heap of the 'folded tab' thrust washers with the tabs all ripped off.

Can't tell you anything about the relative thickness of the trhust washers. It all worked fine (but not as good as my BSA clutch which has very little axial end play). Unfortunately the Trumpet is now at the repair shop recovering from the effects of Mitsubishi that came through 3 lanes of traffic to get me.


Maybe this has all been covered here before somewhere?

Cheers
Ray

Brizzo, As close as I can tell, EVERYTHING has been covered here before at some point! Good luck finding it...covering it again never hurts.

Bernie

The PROPER thrust ring will fit in it's recess in the clutch hub. The WRONG one will flop about.
They are a matched pair.

...and Triumph really fooled Sir Issac Newton with thier setup! Although one shouldn't be suprised, poor old Issac was born a few years too early to enjoy bikes! Science might be totally different otherwise.

GrandPaul, Yes, both thrust washers had the correct ID to fit both hubs, but the MAP one was thicker so in the case of the '72 TR6, it locked the clutch pack when tightening the clutch center nut, but on the '68 T120, it worked.

The BSA washer attempted to comply with Sir Issac's law with a tab on the washer...which was overridden by Murphys law.

Bernie

I just had the same problem with the thicker thrust washer. The new washer measured .059 and the old washer was .047. I put the new washer in and it locked the clutch pack when the the clutch center was tightened down. The old manual calls for .052 - .054 for thrust washers thickness, I took the washer I received from MAP down to .052 and everything works fine.

Jim