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#773381 05/11/19 9:11 pm
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Nick H Offline OP
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I recently finished assembly of my T120 from a total teardown of the engine. I got it running and timed and was about to go for the first ride when I noticed my clutch was sticking. The clutch has mostly new parts and worked fine before the teardown.
Kicking with the lever pulled would not free it. Leaving the lever pulled overnight did not free it so I opened the primary again. Cleaned the clutch plates in kerosene and reassembled and adjusted leaving the cover off. Still sticking. In neutral.
Now it occurs to me that something is wrong - and please be kind. I am new to this stuff.
I took out all the plates and noticed that if I kicked it over, in neutral, that the clutch center and basket both turned and thus turned the primary chain and sprocket and turned over the motor still.
Either I'm missing something very basic or i assembled something wrong, probably both.


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Nick H Offline OP
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Seems I assembled my clutch center wrong. Not sure why but it doesn't spin.


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Maybe the rollers at the back??/ you might have flipped one??

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Nick, three-bolt or four-bolt clutch?


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Nick H Offline OP
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Three bolt. I'll take it apart and report my findings.


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A common problem used to be people fitting 1/4” x 1/4” rollers, which are too long.


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Nick H Offline OP
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So I took it apart. Nothings missing, nothing looks amiss but when I tighten down the clutch securing nut, and not even to 50 ft/lbs, the center becomes too hard to turn.
If the nut is loose, I can turn it but I don't think it spins as freely as I've seen others do in videos.
I don't recall what the rollers measure (although 1/4" sounds familiar) but these parts all worked together before.

Edit: Not quite. Checking my notes I did put on a new early style thrust washer. Found the one I took out and it's a late style.
I guess it's possible this changed the spacing somehow. I'll investigate and report back.

Last edited by Nick H; 05/13/19 7:15 pm.

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Ok you didn’t renew the rollers.

Are you going to tell us what you did renew?

You say it worked fine before you fixed it.


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Nick H Offline OP
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Ok so I got a look at the thrust washer. I have an "early type" clutch hub being a 1968 motor so I had replaced the incorrect late style that was in there on teardown.
[Linked Image]

It was also extremely worn and out of round as you can see in the photo. However the clutch was working like this.
[Linked Image]

Here is a photo with my new early type replacement:
[Linked Image]

My new replacement is quite a bit thicker - .030" than the worn late one - .020" This is the "Premium" washer from the Bonneville Shop by the way.
So now I don't know what to do. Could this be the source of my problem of the clutch center not turning?
Maybe my chamfer faced the wrong way. I find the explanation "towards the rear of the clutch hub center" extremely ambivalent.

Also measured my rollers . They are .235" long and .25" thick

Edit: Just went back out and looked at the chamfer. EXTREMELY important! If I had it faced the wrong way (not sure how I had it) it doesn't lie flat and flush on the hub.
Crapola! That must be it.

Last edited by Nick H; 05/15/19 12:02 am.

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Why do you believe the 68’ came with the early style clutch hub? By 67 if 66 A65s were fitted with the 3 spring clutch. The thrust washer you had would have been correct for the 3 spring hub. Are you fitting the 4 spring basket and centre also?


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Well this ones for a Triumph T120 - not the BSA of another thread of mine.
And according to CBS, both had "early" clutch hubs until 1970.
https://www.classicbritishspares.com/blogs/news/triumph-bsa-3-spring-hub-clutch-thrust-washers


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Apologies, usually when people speak of early clutch parts, they are referring to the 4 spring.


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Put it back together and have the same problem. I don't think I assembled it wrong the first time either.

The clutch center turns freely until I tighten it down with the securing nut - and not even to full torque.

And I don't understand fully why it would turn free when tightened up. The clutch center gets tightened to the basket and to the cover plate behind it.
Checked and doubled checked the parts book and all the parts are there where they are supposed to be including the washer behind the nut.

[Linked Image][Linked Image][Linked Image][Linked Image]

Last edited by Nick H; 05/15/19 11:27 pm.

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Hi,
Wear on the cush drive spider at the back where it clamps up against the shaft adaptor can cause binding
The area that takes the "pressure" as the centre nut is tightened is very small

John

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Possibly the key is causing the centre to distort and lock up the bearing. Check the fit of the key, maybe stone a little off the OD face .


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Originally Posted by chaterlea25
Hi
The area that takes the "pressure" as the centre nut is tightened is very small

John


What area is that?
It seems centre nut is binding the whole thing together and against sprocket cover behind it. Why would it not?

Last edited by Nick H; 05/15/19 11:40 pm.

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"The clutch center gets tightened to the basket..."

No, it should not. The clutch hub's position on the mainshaft is limited by the taper of the shaft. The clutch center can only go to the bottom of the splines on the hub. The chainwheel is sandwiched between the thrust washer and the clutch center, but there should be a few thousanths running clearance.

I think you may be on to something with the thicker thrust washer. I would think a too-thick thrust washer would cause the chainwheel to bind.


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The thickness of a new thrust washer should be .052-054 per the maint manual, that’s a big difference from the .030 of the new one you have. If it were mine I would place some emery paper on a flat surface and reduce the the thickness of the washer until the basket free wheels after being torqued down. If that works maybe it will be ok but it doesn’t tell you what or why there’s a problem.

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Are the rollers raised past the most forward face of the clutch basket?

Other thing is clean the surplus grease off, you don’t need much at all as there will be plenty of oil splashing around the clutch. Put a smear of engineers blue on the back of the clutch centre, bolt it all up, then remove again, if you can slacken it enough so you can just turn the centre, do so and this should help reveal any high spots if any.


Now let’s all have a beer beerchug

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Thank you all for taking the time to read this and offer suggestions!

Alan, my rollers do not extend past the face of the basket. I can see that would cause problems. Good idea about the blue to see where it binds.

It seems the taper on the mainshaft and on the center splines are what should limit the travel of the parts so they do not bind.

Apologies! I'm not so good with a micrometer. My new premium thrust washer measures .055" (not .030!) which is just a tad thicker than the factory manuals .052-.054"

So it should be alright but I also ordered a standard non-premium washer with the locating tabs and will try that. Arrives Saturday.



Last edited by Nick H; 05/16/19 1:32 pm.

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Just out of curiosity I think I would still sand the thrust washer down to .053-.052 and check it assembled. If that works then you would know where the problem was. For whatever it’s worth I’ve always used the washer with the tabs on them and have never had a problem.

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In the pic showing the back of the clutch hub unit I can see the splined centre protruding, this is usually caused by internal wear, however this would not normally give you a bind, normally the opposite.And a slipping/dragging clutch when the wear gets V bad.

Check your new thrust washer ID clears the splined centre protrusion, this is a possible bind.

i suggest you assemble the basket, drum, centre, thrust washer and bearing away from the bike, simulate the centre nut pressure with a clamp and poke around with feeler gauges at the thrust washer to see whats going on, normally there is too much end play and a thick thrust washer is better, you seem to have the opposite problem.
if it all spins well when bench tested then strongly suspect the key fit if it still binds when fitted to the shaft.


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Slight alternate to Gavins comments is to remove the keyway from the main shaft and refit it and tighten the nut. Providing the nut is tight enough you can run the bike without it, I’ve done this for years with mine.

Although it’s worth adding, that I’ve also had the problem with the woodruff key pushing the centre off, although it never distorted the hub, but when it eventually broke loose the hub would spin on the main shaft.


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Well that's interesting because as I'm still struggling with this I tried putting the hub on the shaft without the key as shown in the photo.
It slides on all the way to the back quite easily and will spin. The taper will not hold it at all.
However, with the key in the shaft, the hub only goes so far and does not contact the back.
So I couldn't run it without the key.
[Linked Image]
Do I need a new hub? Or, worse, do I need a new mainshaft or hub centre?

Last edited by Nick H; 05/17/19 12:23 am.

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Hi Nick
Looking again at you photo 4the spider is (as mentioned) protruding
Sometimes the spider is recessed or the ends of the male internal splines get distorted /worn so the thrust face of the
cushdrive body traps the rollers

Looking at your last photo, it looks like the centre adaptor is sitting too far onto the mainshaft?
Or
The mainshaft has moved towards the kickstart side ??
By any chance did you smack the clutch centre extractor to break free the taper?
This could have displaced the bearing on the kickstart side :-(
Or
The clutch centre is split ?

John


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