Author Topic: Clutch Slip  (Read 354 times)

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martinh10

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Clutch Slip
« on: 28 August, 2021, 11:04:29 »
I fitted a new “Triumph-type” four spring clutch from a well-regarded supplier to my 1950 B31 a short time ago and have experienced some clutch slip ever since despite many adjustments. It would be interesting to know if anyone else has had similar problems with these aftermarket items.
To date I have only used Silkolene Gear Oil Light SAE75/SAE85 in the chaincase. On the container it states “Advanced gear oil for wet or dry clutch transmissions. Reduces drag, combats clutch slip and protects highly stressed components. For use in 2T and other separate gearbox machines. Crankcase rating SAE 10W40”. So it sounds like it’s the right stuff for the job but maybe I should try the straight SAE20 specified by BSA. I see from previous postings that there’s quite a variety of opinion on this matter.

Pete C

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Re: Clutch Slip
« Reply #1 on: 28 August, 2021, 12:04:17 »
straight SAE20 every time. I have the triumph 4 spring in a BSA B31, M21 and Triton. No problems with slipping with SAE20.

Modern gear oils are full of friction modifiers which I can't see working with this clutch. I would suggest you strip the cutch, clean the plates with petrol to remove any oil and rebuild. If you grease the bearings, primary chain and the engine shock absorber well, you can run it for a few miles to be sure the clutch is set up correctly before adding oil.
 

Pete C

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Re: Clutch Slip
« Reply #2 on: 28 August, 2021, 12:06:37 »
Some people use ATF for the primary but this should be a specific type of ATF free of the friction modifiers and I can't remember which it is.  :(

martinh10

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Re: Clutch Slip
« Reply #3 on: 28 August, 2021, 12:18:10 »
Thanks Pete, I'm heading out for some SAE20.

idie

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Re: Clutch Slip
« Reply #4 on: 28 August, 2021, 13:56:51 »
I use 10 grade fork oil in my bikes. I know this may be obvious but when you put in the clutch plates you did start with a steel one, The first time I fitted a four spring clutch to my Shooting Star I didn't and had clutch slip.

Pete C

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Re: Clutch Slip
« Reply #5 on: 28 August, 2021, 14:08:50 »
I would use SAE10 oil as well but it is hard enough keeping 20 grade in a pre-unit BSA primary case!  ;D

idie

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Re: Clutch Slip
« Reply #6 on: 28 August, 2021, 17:53:20 »
I had no problem keeping 10 grade oil in the chaincase on my 1949 M33. Use new cork gaskets and some sealing compound.

Pete C

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Re: Clutch Slip
« Reply #7 on: 28 August, 2021, 19:23:11 »
used new corks (heavy grease, no sealant) and even made up these with oil seals but the bugger still drips! I have managed to make a Matchless tin primary leak free though, so I'm still hopefull of eventual success  ;D