7 Plate clutch slipping on T140.

I fitted a 7 plate clutch to my T140 a couple of years ago, and the clutch has always slipped under high load. I fitted 650 springs at the same time as it is recommended, initially tightening the spring until the thread was just entering the straight groove in the spring cap for the screwdriver. To try to stop the slip, I tightened the springs more on two separate occasions so that there was a fair bit of thread protruding through the spring caps to no effect.

So today I have stripped the clutch and found that the extra plain plate that was supplied in the kit is of the often found crap quality i.e. not flat. I have posted a picture of both sides of this plate and also of an original plate. It can clearly be seen where there are high spots. Unfortunately, I bought the kit nearly 3 years ago and so doubt that I can send this plate back. I didn't ride the T140 last year as it was at my sons which has caused a bit of the delay sorting this problem.

I don't know why the clutch is slipping, unless this plate can be soley responsible, but I doubt it.

Any suggestions where to buy a plain clutch plate from that is going to be completely flat? (Like the one's in the Barnett clutch kit for my Norton. Now they were flat).


New plain plate.

Other side of the new plain plate.
Below, an original plate.

Is that the Hyde kit (going by the width of the mark left by friction material)?

Reggie said:

Any suggestions where to buy a plain clutch plate from that is going to be completely flat?

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Should be plenty of good used ones about?

The plain plate in the Aerco kit I bought needed the tangs filing before it would fit, so does that plate slide smoothly on the splines?

I used the 750 springs slackened off about one turn.

I bought the kit from TMS and they sell the Hyde 7 plate conversion, so I assume it is from Hyde.
LAB said;

so does that plate slide smoothly on the splines?

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The plate does slide in and out freely.

I assume that it is correct that when the clutch plates are not assembled in the clutch and therefore there is not any tension on the bolts that the springs sit on, that it is correct that I am able to rock the sprocket/chainwheel housing a bit? Because I can on mine.

Reggie said:

I assume that it is correct that when the clutch plates are not assembled in the clutch and therefore there is not any tension on the bolts that the springs sit on, that it is correct that I am able to rock the sprocket/chainwheel housing a bit? Because I can on mine.

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"a bit" is probably normal.

LAB said;

"a bit" is probably normal.

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Thanks.

I fitted a seven plate Hyde kit with 650 springs to my lightly tuned TR7. It slipped every time the motor reached 5000 rpm. I put the 750 springs in & that helped but it would still slip on hard acceleration. Eventually the friction material started to fall off the plates & then it really did slip! I ordered a new set of friction plates from TMS & these (Aerco) have been better than the Hyde ones. I think I ended up with the 750 springs screwed in until the threads reached the top of the nuts. Whilst this makes the clutch a little heavier to pull it doesn't slip. The simple fact is that the clutch is not up to the job, & whilst it was fine on the 650 engines it simply cannot cope with the extra torque of the 750. One day when I have finished all my other projects I will fit a Commando clutch. The only downside to this is the lack of cush drive.

Martyn.

Hi Martyn, that's quite interesting. I thought that I was nearly the only person having problems with the 7 plate clutch.
I've ordered a new plain plate made by "Suflex," allegedly CNC made, so hopefully it will be flat, and I'll give it all another go. If this fails, I may look at getting some Aerco plates.
I have read up on buying an alloy pressure plate, but it would seem that there is no advantage buying one over the standard steel pressed one, except it looks very nice and shiny when the primary chaincase is removed. Any other thoughts about this?

Reggie said:

I've ordered a new plain plate made by "Suflex," allegedly CNC made, so hopefully it will be flat, and I'll give it all another go. If this fails, I may look at getting some Aerco plates.

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Both 7-plate kits (Hyde and Aerco) are supposedly made by Surflex.

LAB said;

Both 7-plate kits (Hyde and Aerco) are supposedly made by Surflex.

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That doesn't bode well. I will check when it comes.....and hope.

Have you tried flatting the new plate on a sheet of wet & dry paper?

Reggie said:

I have read up on buying an alloy pressure plate, but it would seem that there is no advantage buying one over the standard steel pressed one, except it looks very nice and shiny when the primary chaincase is removed. Any other thoughts about this?

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If the new plain plate was installed as the outer plate then check the pressure plate surface is flat and wasn't applying uneven pressure.

Edit: And, just as a matter of interest, which year model T140 is this?

Also, you might find the plain plate of the 7-plate kit is thinner Edit: (0.70") than the standard plain plates (0.80")?

My Aerco plates have a wider friction area than the Hyde type, but nothing like standard plates. I haven't tried the ally pressure plate as I agree that it's just bling. If the steel one is flat then it should work. One of the most important things to do is to adjust the springs to make the pressure plate runs true when kicking over with the clutch lever pulled in.

I had a chronically slipping 6 plate clutch in a 650 with Surflex plates. Like Mr Matchless above, it happened when the engine was about maximum torque.

Fixed it by doing the very cheap Pete Russell 6.5 plate mod, relining the friction plates with cork mat.

L.A.B. said:

Have you tried flatting the new plate on a sheet of wet & dry paper?

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No, I haven't. I might try it tomorrow on my marble surface although I would think that it would take some time to do and ruin my fingernails at the same time.

L.A.B. said:

If the new plain plate was installed as the outer plate then check the pressure plate surface is flat and wasn't applying uneven pressure.

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The pressure plate surface is flat. I checked it yesterday.

L.A.B. said:

And, just as a matter of interest, which year model T140 is this?

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It's a 1988 Les Harris Bonneville T140.

L.A.B. said:

Also, you might find the plain plate of the 7-plate kit is thinner Edit: (0.70") than the standard plain plates (0.80")?

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I've just measured the extra plain plate and it is exactly the same as the other plain plates which measure at 0.079".
What would be the reason to make the additional plate thinner? The stack height? But would 0.0010" make much difference?

Reggie said:

It's a 1988 Les Harris Bonneville T140.

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Reggie said:

I've just measured the extra plain plate and it is exactly the same as the other plain plates which measure at 0.079".

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Well, I did say "might" but, sorry, it was the late factory clutch that had seven 'thinner' plain plates and six (thinner?) friction plates with an additional friction lining attached to the inside the drum and was fitted to some late Meriden Triumphs so please disregard that piece of information.

Reggie, what was the conclusion with your clutch in the end ?

Fast Eddie said:

Reggie, what was the conclusion with your clutch in the end ?

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It's in my dining room looking pretty and going nowhere fast.


Due to lack of space in my garage the T140 is enjoying life inside my house at the moment awaiting a space in my garage when the sale of one of my bikes is completed, hopefully later this month. Then I will take another look at the clutch before deciding what to do.

I would buy a Bob Newby clutch, but at the moment I'm unable to start the work as the bike is in my house, and I haven't the time or inclination to move the breather away from the primary chain case and all of the work that this would involve. Also with this set up I would lose any cush in the drive train.

The other option is to fit a Commando clutch, but this still leaves no cush in the drive train, plus I assume having the gearbox apart to either alter the gearbox main shaft or put a Norton one in, although I haven't looked into all of it yet.

Once it gets into the garage which should be by March this year at the latest I might start to look at this issue and start to get somewhere with it.

Sorry it's not more positive.