Why does my clutch slip?

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Said before. Still bronze, learned to adjust properly, no complaints, well flogged again Friday & grip is great, haven't taken down in a long time, but I guess I'll gripe when I do because it's never been very enjoyable in my book. I only wish it didn't grip so quickly upon takeoff when cold. 20 min. riding and it's a purring kitten..
 
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However, the end of the main shaft is outboard of the clutch plates and surely centrifugal force would tend to fling it to the area of the circlip of the clutch basket during riding and then drip down into the bottom of the primary chain case when stationary and not onto the plates?

And what about when the bike is parked on the side stand?
I'd say the small amount of gear oil that finds its way along the pushrod tunnel is sufficient to contaminate the pressure plate and outer clutch plates regardless and doesn't readily fling off.


Please correct me if I am wrong, but Norton fitted a bronze clutch originally designed for dry use in a wet use on the Norton?

After nearly five years in production before they changed to bronze friction material?

If I remember correctly I think the infamous JM Leadbeater (aka Beltriveman) said it was the original Commando clutch that was supposedly designed as a 'dry' clutch.

Although introduced on the late 750 models (from 212278) in my opinion the 5-'bronze' plate clutch (replacing the previous 4-fibre plate) was an upgrade in readiness for the soon to be introduced 850 models.


Is the surflex clutch more tolerant of wet use?
What is the consensus of opinion on the best suppliers of a clutch nut with a seal?


I never found the bronze plates to be intolerant except before I fitted the dynodave pushrod seal.
Since trying a set of Surflex plates I'd say neutral is easier to find, 1st gear selection is smoother and clutch engagement more gradual than the bronze plates.



You have mixed up the gearbox component locations!
the circlip is:
1. at the OD of the main shaft
2. near the end of the sleeve gear
3. far short of the mainshaft end, yes at the back and outside of the clutch drum.

He means the clutch diaphragm spring retaining circlip.
 
Why does my clutch slip?
 
My 74 Commando had the OEM clutch until I recently installed the CNW electric starter kit and switched to Barnett plates. In all the years of riding I noticed a few things regarding the clutch, some of which have been discussed in this thread:

1- The bike needs to be used at least once a month. Otherwise, the residual oil that makes its way between the plates will thicken and cause slippage.
2- The clutch is happiest with 1-2 ounces less oil in the primary than called for.
3- It's best to use a light viscosity oil in the primary case; 10w3o worked best for me.
4- It's inevitable that some seepage will occur from the crank seal and/or the transmission. I used drain a bit of oil out of the primary every 2 months or so.
5- If slippage occurs the best course of action is to disassemble the clutch and clean all plates in solvent.
 
Neither of my Nortons - my original 750 back in the day, or my current 850 - suffered from clutch slippage due to oil 'contamination' or ever required any clutch cleaning and neither had/has a gearbox/chaincase seal. I used engine oil in the chaincase of my '71 for the 10 years I owned it. I've used ATF in my 850 since a few weeks after I purchased it in '06.

IF gear oil will cause clutch slippage, as opposed to engine oil or ATF, I would have to conclude that neither of my bikes have ever had gear oil migrate into the chaincase for whatever reason...;)
 
Neither of my Nortons - my original 750 back in the day, or my current 850 - suffered from clutch slippage due to oil 'contamination' or ever required any clutch cleaning and neither had/has a gearbox/chaincase seal. I used engine oil in the chaincase of my '71 for the 10 years I owned it. I've used ATF in my 850 since a few weeks after I purchased it in '06.

IF gear oil will cause clutch slippage, as opposed to engine oil or ATF, I would have to conclude that neither of my bikes have ever had gear oil migrate into the chaincase for whatever reason...;)



Certainly wasn't my experience on my 850 back in the day.
Was your bike stored on the center stand or side stand?
 
The last time I pulled my clutch apart was just over 7 years ago to replace the clutch centre, the bronze plates haven't been out since and no slip at all and has done well over 25k miles since, running between 5 to 7 fl oz of ATF F no more than that for the primary chain, I have never had gear box oil find its way into my primary as I don't over fill my gear box, I do pull my primary case off on every oil change to make sure everything is right inside, been doing it this way for 44 years now and the only time I had clutch slip was in the first 2 years when running motor oil in the primary as recondmented by the bible (workshop manual) till I started to run a lighter oil and less oil than the 7 fl ozs.
I have worked on other Nortons where the owners have had bad clutch slipping and found they were running to heavy oil and way over filled, thinking running more oil will help the chain being lubed better and will get more life out of it, all that does is cause more problems.

Ashley
 
Certainly wasn't my experience on my 850 back in the day.
Was your bike stored on the center stand or side stand?

Sidestand. And on the SS the oil level in the gearbox is still below the clutch rod. IOW, I can't see how oil can migrate from the gearbox in the first place! HOWEVER, from all the comments and the fact that an aftermarket seal exists, obviously it does in some cases.

TBH, I've always attributed it to overfilling the gearbox but I admit it's hard to believe that so many experienced folks are overfilling their gearboxes! Wonder if there could be something in the fitting process at the factory or tolerance of parts that create enough variation to cause it in some bikes and not others?
 
I totally understand that some folks have to pull the bronze clutch and clean it periodically and some don't need to and that their are strategies (no parking on the sidestand for long periods etc.) and differing opinions on lubricants, but if the lifetime bronze-plate were such a good idea, modern bikes would be full of 'em and there are none that I know of. Fiber clutches on modern high-power 4-cylinder machines last 80-100K miles with little or no attention. If oil with friction modifiers is avoided, they never slip and only wear out when abused.

The clutch in The Titanic was half fiber and half bronze and I happened to have enough fiber plates still in spec, so I pulled the bronzes. No sure what the thinking was there.
 
Sidestand. And on the SS the oil level in the gearbox is still below the clutch rod.


The open mainshaft timing-side bearing is lubricated by splash from oil thrown around inside the main case, some of which will either pass through or be flung from the bearing and onto the lifter ball and then migrate from the ball to the pushrod and get into the mainshaft tunnel.

When the bike is parked on the side stand then gear oil the in the mainshaft tunnel oil is obviously going to run in the direction of the primary.

It would of course be possible to fit a shielded T/S mainshaft bearing but then the lifter mechanism would be starved of lubrication.
 
Hi All
Greetings from hot, sunny and excellent southern Italy. I see my little location flag has changed from the UK flag to an Italian flag so you know where I am . Spooky. :)
Exactly as LAB has said; I was surprised to see the hole through my main shaft filled with gearbox oil when it sits 2” (?) above the oil level in the gearbox. It is filled to the level plug. Before I left for Italy I determined that the gearbox main shaft ends roughly inside the inner cup section of the diaphragm spring. I always park on the main stand, but as LAB said the oil is likely to drip from the cup section into the area of the pressure plate and the outer clutch plate. But I have never seen it contaminated the ATF oil. I probably need some vino rosso to consider matters further:)
 
Greetings from hot, sunny and excellent southern Italy. I see my little location flag has changed from the UK flag to an Italian flag so you know where I am . Spooky. :)

That's technology, not spooks as the system identifies the approximate area you are posting from and selects the appropriate country flag! ;)


But I have never seen it contaminated the ATF oil.


I think people get the impression that it's a considrable quantity instead of only enough to contaminate the friction surfaces.

Next time I suggest you use your nose! If the plates are contaminated with gear oil then you can usually smell it!
 
The clutch in The Titanic was half fiber and half bronze and I happened to have enough fiber plates still in spec, so I pulled the bronzes. No sure what the thinking was there.

That is how mine were since I bought it 30 yrs ago.

According to Windy, that was a common stack up years ago, as the black Barnett plates were seen as very aggressive.
 
The clutch IS a little abrupt, probably the least smoothest part of the bike. Of course, like everyone else, I've grown spoiled by hydraulic clutches.
 
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