Atlas clutch lever pressure

I am currently rebuilding a late 1966 Atlas, the clutch lever takes considerable amount of pressure to use considerably more than my other bikes which include a 1967 650SS, 1957 ES2 [both of which have a similar clutch] or my 1969 Fastback. The Atlas has a brand new drum [RGM] 7/8 lever pivot, I have purchased new springs [no difference], my cable is new and routed the same as my 650SS, I am now looking at the gearbox end and note the activating arm is different between Dommy 04-0029 and Commando 06-0715, has anybody tried a Commando arm or haver any other suggestions?

Welcome to the Atlas clutch!

There is plenty of reading below (similar threads).

The best single thing you can do is change your clutch cable to a Venhill, which is a Teflon lined cable. It is said to reduce clutch pull by 25% and I would concur that.

After reading below, come back with any questions.

Slick

Are you using V clutch plates and not the square type plates?

original plates that it came with, as yet I have not had the bike going as have been doing a full rebuild, I believe the bike has basicly sitting for 30+ years

Check the clutch centre, if the cut slots are worn you will never get the smooth operation of a Norton clutch. Ditto the outer cage slots

David Corneau has done some investigation regarding the Norton-clutches. Have a look here http://atlanticgreen.com/ndnsclutch.htm see at «Atlas Actuator»

The clutch centre [drum] is new supplied by RGM.

Did some checking on some old notes I've made. Did some testing a year ago on a couple of sets of clutch springs.
One of the tests was to find the force needed to compress a spring to 30mm length. New Andover spring 63Kg. Old Manx spring 38Kg. Old 650SS spring 30kg. RGM65Lbs spring 35Kg. No measure on RGM 86Lbs spring. The tests was not made up to any scientific standard, but they indicate how much difference it can be with different springs.
By the way, this time you get spellling of pressure right

The spring tests done by Mike40M are interesting. However it would be a mistake to alleviate clutch pull in an Atlas by swapping to other springs.

The Atlas springs are heavy because they are what it takes to harness the torque of the 750 engine.

The AMC clutch used in the Atlas started life as the clutch for a 25 hp 500 cc engine, then was applied to 600 cc, and then to 650 cc engines. Somewhere along the way, it gained another plain and friction plate, but when it was applied to the Atlas, more clamp pressure was needed to harness the torque, hence the stiffer springs.

Barnett plates are "stickier" than the original, designed to operate in oil, as opposed to the original which were not. Then, if Ford Type F ATF is used in the primary, rather than oil, some spring pressure can be relieved by backing off on the recommended spring nut tightening. With a Venhill clutch cable, the lever pull can be reduced to a manageable level, but still four finger.

The drawback to Barnett plates, is that they stick, and the clutch has to be freed up before starting, something that was never necessary with originals. If one changes to Barnett plates, assemble the clutch stack with oil. I assembled mine dry, and had to pull the primary cover and pry the plates apart with a sharp tool to free them up.

I backed the nuts off 1/2 turn from flush and the clutch has no slip. If I should find it necessary to pull the primary cover, I will back off another turn.

HTH

Slick

Thanks guys for your assistance, I have reprofiled the activating arm and tidied up the rollers, I will re assemble check the cable and hope for the best otherwise it will be remove the primary cover and recheck springs & cups [again].
Thanks Al

I have had good luck replacing the handlebar levers with the EMGO copies of the spanish AMAL levers used on Bultacos etc. These are cheap at $30 / pair, look good and perform well