67 Atlas clutch

I'm thinking that thee clutch on my Atlas is getting close to needing an overhaul or replacement.
It's ridiculously easy to pull, and engagement occurs almost at the complete end of the lever travel; not smooth and somewhat abrupt. The 3 clutch basket springs are tightened to where the tops of their heads are flush with the clutch surface.
No amount of cable adjusting seems to change anything.
I have cleaned and reassembled the plates (can't remember how many of which plate), and it still didn't improve things much.
Do I just need to by new disks and plates? Again, don't know how long theses were on the bike.
Any other tips?

The typical Atlas clutch is a "bear" to pull in. Any Atlas guy would welcome a "ridiculously" easy to pull clutch, assuming it did not slip.

Your description does not fit a normal functioning Atlas clutch. Is the clutch slipping?

The proper spring tensioning is with the retainer nuts flush with the studs.

Do the plates fill the basket, or is the pressure plate well below the basket top?

It is well to check the condition of the cushion rubbers in the clutch center, as well as the center body or "spyder", which are notoriously prone to breaking. And while you are in there, check that there is no cratering on the splined hub.

Slick

Have you checked that the little breather hole in the fuel cap is open, and not blocked.
If the tank can't breathe, it starts to get a slight vacuum with a few miles,
and fuel flow can become slow, to the point where it maybe can't keep up.
If it stops, the fuel flow can catch up.
Just a thought...

Rohan said:

Have you checked that the little breather hole in the fuel cap is open, and not blocked.
If the tank can't breathe, it starts to get a slight vacuum with a few miles,
and fuel flow can become slow, to the point where it maybe can't keep up.
If it stops, the fuel flow can catch up.
Just a thought...

Click to expand...

A good point by Rohan, but it belongs with the other thread by wjrich.

texasSlick said:

A good point by Rohan, but it belongs with the other thread by wjrich.

Click to expand...

Indeedy.
Clicked on that itty bitty little icon, to go to the end of the thread, but must have hit the wrong one.

Here is a link for a description of the Atlas clutch:

http://www.andover-norton.co.uk/SI%20Clutch.htm

I have found best prices on clutch parts to be from AMC Spares in the UK. Prices justify shipping cost from UK.

http://www.amcclassicspares.com

BTW ..... I installed a Venthill Teflon lined clutch cable .... Venthill claims they reduce clutch pull 25%. I would agree with that number. Of coarse, if yours is "ridiculously easy" to pull, you will not want one. You may want a "rust" lined one, just so you can be like the rest of us Atlas guys.

Seriously, keep us informed about what you find in your clutch on further inspection.

Slick

Texas Slick -
Clutch lever effort is way too light compared to my Commando and HD. You can literally work it eaisly with pinkie finger. It will slightly slip if accelarating hard in 2nd or 3rd around 4k rpm. Clutch engagement is way towards the end of the lever travel, which doesn't seem correct either.
Going to take the outer cover off this weekend and take apart for a better look and report back.
Thanks

So I opened up the primary yesterday and took apart my clutch. Last time- couple of years ago when I last disassembled to clean plates, I didn't pay attention to plates, just put them back in the way I took them out. Since the plan was to replace plates, I ordered the 5 new friction plates assuming- incorrectly- that I had all the other plates.
Here's what I took out this time, starting with the 1st plate removed
- 1 sided friction plate
-2 sided friction plate
-1 sided friction plate
-1 plain steel plate
-1 sided friction plate
- 2 sided friction plate
Not quite what it says in the manual- new friction and plain plates on order from AN.
Also, red drop of fluid on the end of the clutch rod, so ordered 1 of Dyno Dave's seal kits.
Updates to follow...

A great many years ago I talked to Mr Doug Hele about clutches, especially T140 and Atlas lumps or clutches as the manufacturers INCORRECTLY described the lumps. Mr Hele suggested that the correct clamp load clamping the friction interfaces together for both was around 250 lbf (pound force) with the clutch fully engaged. Thus to START to free off the lumps YOU have to apply to the pressure plate a load of approx 250 lbf and as you pull the clutch lever back to the bar you are compressing the springs towards their coil bound state and the 'grunt' required to do so rises and for the T140 lump after 0.080 inch of lift the grunt required has risen to approx 285 lbf. Mr Hele suggested that for the Atlas lump it was around 300 lbf. (At the time I only had some T140 springs tested).
The original 750 Commando had a clutch lever easily pulled back to the bar with two fingers and the INITIAL release load required was approx 210 lbf and after approx 0.080 inch of lift approx 150 lbf. The original Commando diaphragm spring being 0.075 +/- 0.0015 inch thick. The LAST version of the spring fitted to the late 750 and all 820 models being 0.084 +/- 0.0015 inch thick and requiring an initial release load of approx 300lbf and after approx 0.080 of lift approx 250 lbf....which explains why some Commando clutches are light to operate and others ridiculously heavy. NOT that many Commando owners even know Norton employed 4 different diaphragm springs in the clutch........each new version giving a higher clamp load and requiring more grunt at the clutch lever than the previous version.........

There is NO way An Atlas clutch lever could be easily pulled back to the bar if correctly assembled with correct components because in traffic they were BASTARDS...just like poxy T140 ones. On a motorway with no gear changing required they were beautiful !!

while you have the clutch apart, check the cush rubbers, especially if any of the tabs on your clutch plates look slightly misshapen.

also, if the clutch lever was replaced, check the pivot length. originals should be about 7/8", later clutches and many replacements are a little over an inch. This slight change in pivot length makes a big difference in pull pressure - 20% or more. Every little bit helps

3 of my bikes have this same clutch, so have some experience with them. In fact, I re-installed the original clutch on my '61 last night - 3-finger pull.

Finally got around to getting back to work on the clutch. Got friction and steel plates from AN and mi rod seal from Dyno Dave. All arrived quickly, and thanks to Dave for the phone call with my additional questions- great service from everyone involved!

I can't find a reference on installing the plates- not the order, but do i need to treat them with anything? I recall hearing things like soaking them in oil, etc.

wjrich said:

I can't find a reference on installing the plates- not the order, but do i need to treat them with anything? I recall hearing things like soaking them in oil, etc.

Click to expand...

Be sure to check those cush drive rubbers before putting clutch together!

Re: soak in oil ..... you start with a dry clutch, add oil, ride 10 minutes, you now have a wet clutch!

I recently put new Barnet plates (friction and plain) in mine. I left them dry, and the bike sat for months while I turned my attention to other issues. When I got around to the clutch again, I found I could not free up the clutch, and had to pull the pressure plate again. The plates were so stuck together, I had to take a lever to separate them. I then put a light film of Ford Type F ATF on the plates and have not had the problem return, although I am now squeezing the lever every so often.

Since the plates will foul with oil after normal use, I see no problem coating them at the outset.

BTW .... use 7 Oz of Ford Type F ATF rather than oil.

Slick

Will go for the ATF.
Rubbers appear to be servicable.
I put the clutch together dry and tightened down the springs, etc., and finally the pull feels normal- not too hard, not too soft. Going to put everything back together and see if I can get a little road time in today.

With a not too hard clutch lever pull I can only wonder what clutch you have fitted?? Does it have 5 plain steel interplates along with 5 double sided friction plates along with a single sided friction plate, a plain clutch basket and a clutch back plate with friction material bonded to it giving a total of 12 fiction interfaces? Are the springs the correct springs an d adjusted correctly as per the book??
According to Mr Hele when I a great many years ago 'consulted' him re Norton and Triumph clutches he stated that the the release load for the Atlas clutch reached around 300 lbf(pounds force) with the lever back to the bar. For a T140 the initial release load is approx 250 lbf and after 0.080 inch lift 280 lbf and they are b*******s to operate after a few minutes stuck in slow moving trafficdoing a lot of gear changing!! Triumph to increase the clutch torque capacity for the 750 motor took the 650 clutch and fitted 30% stronger springs even though one Motor Cycle Sport road test had said of a 650 clutch something like..' it was easy to change gear without using the clutch lever which was just as well as clutch lever action was heavy'. Personally I suspect Triumph had fitted 750 springs to reduce the chance of clutch slip during the road test......
For comparison the release load for a Commando clutch fitted with a correctly set up 0.084 inch thick diaphragm spring as fitted to late Commando models gave a clamp load of approx 550 lbf and required a release load of initially approx 300lbf and with the lever back to the bar approx 250 lbf compared to the diaphragm spring employed on the ORIGINAL 750 Commandos which gave a clamp load of approx 380 lbf and required an initial release load of approx210 lbf and after 0.080 inch lift approx 150 lbf. Guess why early Commandos had an easy two finger MAX clutch lever action......
Wonder what clutch you have fitted?? An ES2 or 88/99 one perhaps in which case don't 'wind on' the throttle because if you do you will sit there going no where fast with a slipping clutch.
The LAST thing you clutch needs is ATF oil in the chain case as it contains friction reducers which when it reaches the designed to be run dry clutch friction interfaces only help the clutch to suffer from even greater slip problems. The oil was intended to be, when the Norton pressed steel oil bath chain case was developed in the 1930s, SAE 10 or 20 straight engine oil and they even put an OIL EXCLUDING BAND around the basket in an attempt to stop oil from entering the designed to be run dry clutch! My later BSA A65 factory manual recommends Castrolite a very thin (Knats piss) SAE10-40 oil but I dont think it has been available in the UK for decades. I believe Silkolene or someone supply a SAE 20 straight engine oil in quart pots.....
Of course having read your copy of the Norton 'Maintenance Manual and Instruction Book for models %0, ES2, 88, 99, 650, Sports Specials, 750 Atlas and 750 Scrambler' you will already be aware that the clutch was designed to be run dry as on the problems pages(86/87) it states one reason for clutch slip to be and I quote 'Oil on plates (usually caused by overfilling oil bath)' with the remedy given as 'Dismantle clutch plates and wash in petrol'....a ritual OFTEN performed in my youth but in those days of youth the throttle had only one working position putting all the torque through the clutch the engine could supply .....Of course in those days many died doing so!!

The AMC clutch, as well as the Cdo clutch, were meant to be run dry, but anytime I ever disassembled one, I found the plates to be soaked with oil, and the cush drive rubbers (Buna N? supposedly oil impervious) were "gummy".

Somewhere in my past, I was informed Ford Type F ATF (Type F has no friction modifiers) gave 35% greater friction coefficient than oil. My source (?) of this information may be incorrect, but I have accepted it. ATF is also said to be inert to Buna and other elastomers. As long as the clutch will foul with oil, I figure 35% greater friction is a benefit. Thus I use and recommend it. In theory, one can slightly back off on the spring nuts and get the same torque capacity, thus giving a slightly lighter lever pull.

Slick

Many years ago Heinz worked at the Norton factory on Bracebridge Street. He was able to acquire a blank AMC clutch hub to play with. He machined it so that the slots on the hub were at an angle and caused the clutch to servo together. He said that under load it wouldn't slip.
Years later he and a friend built another one but not having a blank hub machined the basket and plates instead. The friend still has and rides the bike and it is a 2 finger clutch.
Heinz told me that management liked the idea but only because they could reduce the number of plates and save money. He said that it wouldn't work with less than the stock stack of plates.
Trying to get pictures from my friend to post so you can see what I'm trying to explain.

John in Texas

Clutch assembly is per the book- five double sided friction plates, 5 sintered plain, and 1 1-sided plate.

If I can get the primary cover to actually seal, I can report back on the ATF v oil discussion...

wjrich said:

Clutch assembly is per the book- five double sided friction plates, 5 sintered plain, and 1 1-sided plate.

If I can get the primary cover to actually seal, I can report back on the ATF v oil discussion...

Click to expand...

I have read that the primary cover will leak oil no matter what you do to it. In truth, it can be made oil tight, or at least spot no more than a quarter sized puddle in 2 to 3 weeks of standing.

I just today fitted my cover. Here is my method:

Bond a new thick rubber gasket to the inner cover using RTV.
Smear a coat of RTV on the outer cover flange, from half way up one end, across the bottom, and half way up the other end.
Apply a generous bead of RTV to the edge of the thick rubber gasket half way up and across bottom as described for the cover flange. Apply a generous bead to the shoulder of the primary cover - the shoulder is where the sealing flange steps up to meet the edge of the thick gasket when the cover is pressed on.
Tap the cover on with a rubber mallet. Do not over-tighten the big central nut - 2 to 3 exposed threads is sufficient. It goes without saying, the parts should be clean and oil free before applying RTV.

Allow 48 hours for the RTV to cure before adding ATF. Don't worry .... the cover will come off when necessary.

Slick

However, you sure as heck better be sure everything inside the primary case is ship-shape, cause it's a royal pain in the ass to
keep redoing an oil tight assembly. After the regimen described my primary leaks perhaps one drop of ATF every week. Breaking
loose the RTV can be a challenge while not distorting the outer cover, but doable.

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I am trying to post pictures of the clutch modification. Check it out, what a very clever man Heinz was.

John in Texas