Mk111 Heavy + Dragging Clutch Advice Please

[GRM 450]

Gents,
I have read as much as I can on this issue but I'm not sure on a few things.
1977 Mk111 that was rebuilt at 12 k miles.

At this time I fitted a Barnett clutch which has steel plates with friction plates.
I've since travelled 14 k miles and lately the clutch as become noticeably heavier to operate (could be I'm just getting weaker with age) and doesn't disengage completely. Seems to drag making neutral hard to find.

Cable is not at fault I'm pretty sure, and all adjustments seem ok.

I removed the clutch and washed in petrol as it did have a slight gear oil smell.
Checked the inner and outer clutch basket for wear, the inner has slight marks from the two middle fibre plate's teeth, the rest are ok. The two middle fibre plates teeth are slightly worn. But they slide over the centre driven cog easily.

All the steels are like new.

The clutch operating lever and the operating roller appear to be in good order.

After washing the plates in petrol I oiled them with engine oil and reinstalled the clutch and pressure plate, adjusted as per the manual.

I doubt it will slip, as it didn't before, and I think the dragging was dirty contaminated plates.

But it still seems hard to pull the lever. We measured it at 10kg and over at the lever.

Any advice re the heavy pull ????

Regards
Graeme

 

[worntorn]

Switching to a Venhills cable and correcting the stack height gave mine 7 lb (3 kg) pull. Same clutch as yours, Barnett.
Before the changes it was similar to your clutch for pull.

Glen

 

[lazyeye6]

The drag pulling the lever is one issue. Clutch drag is another. Have you ever lubricated the clutch cable?
On the other issue, why would you want to lublicate your clutch plates with engine oil, or any oil for that matter.
They are meant to be dry, or reasonably so.
So recent heavy clutch pull and difficult plate disengagement suggest that your clutch plates are gluing themselves
together with the oil. Why are your oiling them?. I suggest dismantling your primary side and removing your
clutch plates. Clean them thoroughly and re-install them. .

 

[MexicoMike]

I'm sure it's the setup of the clutch discs/steels and the associated stack height. You probably have too much clearance between the pressure plate and the snap ring. I have essentially the same clutch setup and the clutch is comfortably light and no slippage at all.

Old Britts used to have various thickness steels to get the proper clearance - don't know if they still do.

I don't agree at all with the idea that these are supposed to be "dry clutches." They are clutches in a chaincase with engine oil (originally) flying around so they are, by definition, wet clutches...or at least "semi-wet" clutches. No engineer or designer expected them to magically stay dry in that environment.

In any case, the problem you are describing is stack-height related.

 

[Peavey Jeltz]

Stack height. See https://www.accessnorton.com/NortonCommando/heavy-clutch-stack-height.19547/ and others on this forum.

 

[worntorn]

I made the changes 1 at a time and measured resistance.
Changing from a freshly lubed standard cable to a Venhills stainless/Teflon Featherlight reduced lever pull from 27lbs to 15 lbs, nearly in half.
Setting up stack height cut the pull in half again, 15 lbs down to 7.

I can pull the lever in with one finger now.

Glen

 

[GRM 450]

Thank you all for your replies and advice.
I will read the links again.
It's a Mk111 with electric start and a sprag and chain so must be oiled. plates get oil on them so that's why I oiled them to measure the oiled thicknes.
How much clearance should there be between the spring circlip and the pressure plate?

Regards
Graeme

 

[MichaelB]

I made the changes 1 at a time and measured resistance.
Changing from a freshly lubed standard cable to a Venhills stainless/Teflon Featherlight reduced lever pull from 27lbs to 15 lbs, nearly in half.
Setting up stack height cut the pull in half again, 15 lbs down to 7.

I can pull the lever in with one finger now.

Glen

Good info there. Well done!!!

 

[MichaelB]

Thank you all for your replies and advice.
I will read the links again.
It's a Mk111 with electric start and a sprag and chain so must be oiled. plates get oil on them so that's why I oiled them to measure the oiled thicknes.
How much clearance should there be between the spring circlip and the pressure plate?

Regards
Graeme

https://www.oldbritts.com/ob_clutch_info.html

 

[lazyeye6]

Thank you all for your replies and advice.
I will read the links again.
It's a Mk111 with electric start and a sprag and chain so must be oiled. plates get oil on them so that's why I oiled them to measure the oiled thicknes.
How much clearance should there be between the spring circlip and the pressure plate?

Regards
Graeme

Having re-read your original post, I understand that, for whatever reason, you have abandoned the original steel and bronze
clutch plate system and have stubstituted a Barnett set of plates. The total thickness of this set of plates must be close to equal
that of the set removed. If even a tiny bit less it will result in a hard pull. There should be little to no space between the circlip
and the pressure plate. Apparently Old Britts used to sell spacer plates of various sizes to deal with this phenomenon. It is said
that they no longer do so. I have found that oiling the Barnett plates results in the plates sticking together after a period of time and
difficulty shifting due to the plates sticking to each other. I have a set of Barnett plates and I store my bike with the clutch lever pulled in.
You will soon learn why.

 

[GRM 450]

Thank you all,
I measured the gap at 1mm tight between the pressure plate and the spring clip.
I dug out the box with the original clutch hoping to find a steel plate to use as a fill in but only the bronze plates were there. So I must have re used the steel plates when I fitted the Barnett friction plates.
I will buy a set of new Barnett friction plates as they aren't expensive and see how they fill in the gap.
And a new venhill cable

Graeme

 

[GRM 450]

And new steel plates seeing the ones I have must also be worn

 

[worntorn]

I use type F ATF in the primary with the Barnetts. Years ago, a Norton owner suggested the type F for the primary.
I was having trouble selecting neutral due to clutch drag. A couple of days with the type F in there solved that problem.
After a winter sit it releases perfectly, no need to tie the lever back.
No dragging plates either, it's a lovely light, progressive clutch to use.
Some have found that the ATF did not have enough viscosity to let the hydraulic adjuster do its job.
My hydraulic adjuster works fine with the ATF, but it would be good to check the adjuster action if you switch to the Type F ATF.

For anyone with sticking, dragging clutch plates, you may need a Dynodave clutch pushrod seal added. Ive got one on the MK3 and the Dommie version on the 650SS.

Sticky Gearbox oil getting on the plates makes for a dragging clutch and possibly plates sticking together if left sit.

Glen

 

[maylar]

I've since travelled 14 k miles and lately the clutch as become noticeably heavier to operate (could be I'm just getting weaker with age) and doesn't disengage completely.

Lately? Has it changed? When you get the clutch apart again check the clutch center nut, it might have come loose.

 

[eskasteve]

Sounds like a couple of things to me since the problem has been progressive rather than all of a sudden. First off, I can't see how the stack height could change. Gear oil will make your clutch drag. Old cables will make the pull harder as the lube gets used up. Venhills cables, as worntorn said, is a good step in the right direction. The clutch center nuts do come loose changing the adjustment on the clutch pushrod. I'd do a bit of forum research on the different methods of stopping the transmission fluid from entering your primary case.

 

[L.A.B.]

On the other issue, why would you want to lublicate your clutch plates with engine oil, or any oil for that matter.

It's apparently what Barnett recommends:
https://www.accessnorton.com/NortonCommando/barnett-clutch-friction-plates.20696/

"Engine oil" (20W/50) because it's an 850 Mk3. Personally, I don't recommend using ATF in the Mk3 primary as in my opinion (also various other Mk3 owners) that the hydraulic primary chain tensioner doesn't work properly with ATF.

First off, I can't see how the stack height could change.

The stack height will reduce as the plates wear which would result in a heavier clutch pull but I wouldn't expect that to happen over a short period of time.

 

[lazyeye6]

It's apparently what Barnett recommends:
https://www.accessnorton.com/NortonCommando/barnett-clutch-friction-plates.20696/

"Engine oil" (20W/50) because it's an 850 Mk3. Personally, I don't recommend using ATF in the Mk3 primary as in my opinion (also various other Mk3 owners) that the hydraulic primary chain tensioner doesn't work properly with ATF.

I agree that Barnett recommends lubing the clutch plates on installation. I have done so, using ATF. It soaks in, and then I have carefully
wiped off all excess. I have a belt drive, so a dry primary. I have a clutch rod seal installed. I am not shy about taking the primary apart
just for fun and find every time at least some of the plates are stuck together. If I don't fasten back the clutch lever while in storage I
will usually experience a jerk on shifting from neutral to 1st when cold. Perhaps I should be more liberal about oiling my clutch plates,
or ride more frequently?

Slick said'
"I installed new Barnett friction and plain plates in my Atlas basket DRY, and left the assembly with spring pressure set for some 6 months while I attended to other things on the bike. When I got around to cranking up, I found that I could not free up the clutch. With the clutch lever pulled all the way to the hand grip, I was turning over the engine as I kicked on the kickstart lever. When I disassembled the clutch, I found several plain and friction plates were positively stuck to each other, effectively locking the clutch. After applying ATF to the friction plates, the clutch freed up as one would expect, even after more months of non use."

While I I only have a Mk 2 now, I used to have a Mk 3. I found that when using ATF in the primary, the chain tensioner was not priming
itself properly and the chain would clatter for a minute or so on cold starts. I switched to 20w/50 in the primary and the problem never occurred again.

 

[MichaelB]

"I switched to 20w/50 in the primary and the problem never occurred again."

'Caution, thread drift'....

I had a Mk 3 years ago and the only way I could stop the rattle at start up was to increase the idle to about 1200.
The bike is gone now but I wondered if the primary chain had stretched beyond limits.
Is it normal to increase the idle to 1200, or was something amiss?

 

[L.A.B.]

I had a Mk 3 years ago and the only way I could stop the rattle at start up was to increase the idle to about 1200.
The bike is gone now but I wondered if the primary chain had stretched beyond limits.

With which type of oil in the primary chaincase?

Is it normal to increase the idle to 1200, or was something amiss?

I would guess the higher speed keeps the primary chain under more constant load so prevents the chain thrashing until the tensioner has reprimed.

 

[bill]

Another way to adjust the clutch stack up highth is to mix 850 and 750 frictions