Help with clutch

New to these forums and as of a week ago I'm a new owner of a 1969 750 Commando (my first Norton).

When riding the bike home, the clutch dragged horribly and also took forever to completely catch. No big deal, I planned on going through this thing and knew that stuff like carbs and clutches were going to need attention. I've read all I could find Including the David Comeau "easy pull, no drag" along with his Norton Commando Clutch Pack articles, the "Commando Clutch Plate Information" article by Fred Eaton.

First thing noticed when I pulled the clutch apart was that the bike had been upgraded to a 850 style clutch using 4 Plain and 5 Friction plates. So I get the dial calipers out and find that the plain plates are still at 0.080" but are without any grooves, and the friction plates are measuring out from 0.116" to 0.117". So I take a little run over to my local Norton shop and buy a set of 5 Barnett friction plates. I throw the calipers on the stack (5 friction 4 plain & the pressure plate) and it comes up 0.070" short of the recommended "late clutch" stack height of 1.172"!!! I do a double take and measure the pressure plate alone, which comes up with a thickness of 0.173", which is much less than the 0.227" David Comeau reports. I look at the clutch basket and see what appears to be a plain clutch plate welded to the clutch basket:



I'm guessing this could be a custom (thicker) backing plate as discussed by Comeau? I'm open for suggestions and directions I could go with next to sort this thing out.

Thanks in advance!

no doubt other will disagree but

I assume right now you have the main spring being held slightly flexed by your official tool....

what I would do at this point is to put a steel plate in the back of the basket then friction then steel, etc

then when you get close to the basket being full put the final very thick end plate on see if the full stack is at the point where
you can put the main spring held by tool in place and just be able to thread the big cir clip in its groove, tapping it in around
so it is fully seated, then remove main spring tool

screw in the adjuster bolt until it is lightly seated and back it out 3/4 of a turn and nip the nut

in theory the clutch is now set, providing the cable end is in place on the arm in the gearbox and the arm has not "fallen"
in which case you release the nut and screw out of the adjuster enough to get play in the arm

all ok, then set the handlebar cable so you have about a nickel clearance

put on center stand and in neutral see if it snicks into first and then neutral and second easily, if so you got it right and go ride

all the measuring you are talking about is an exacting science that, in my humble opinion is all well and fine but not that necessary

Hi Strong Bad.
Re: "...I look at the clutch basket and see what appears to be a plain clutch plate welded to the clutch basket:"

Looks like a clutch basket to me as there is no teeth on the "...plain clutch plate welded..." you show in your picture.
Love the big stabilising washer under the clutch centre nut.
By the way, were the clutch plates oily when you removed them?
Ta.

1up3down said:

no doubt other will disagree but

I assume right now you have the main spring being held slightly flexed by your official tool....

Click to expand...

Why yes it is, should I relieve the tension on it?

1up3down said:

what I would do at this point is to put a steel plate in the back of the basket then friction then steel, etc

then when you get close to the basket being full put the final very thick end plate on see if the full stack is at the point where
you can put the main spring held by tool in place and just be able to thread the big cir clip in its groove, tapping it in around
so it is fully seated, then remove main spring tool

screw in the adjuster bolt until it is lightly seated and back it out 3/4 of a turn and nip the nut

in theory the clutch is now set, providing the cable end is in place on the arm in the gearbox and the arm has not "fallen"
in which case you release the nut and screw out of the adjuster enough to get play in the arm

all ok, then set the handlebar cable so you have about a nickel clearance

put on center stand and in neutral see if it snicks into first and then neutral and second easily, if so you got it right and go ride

all the measuring you are talking about is an exacting science that, in my humble opinion is all well and fine but not that necessary

Click to expand...

Thank you for your input!

needing said:

Hi Strong Bad.
Re: "...I look at the clutch basket and see what appears to be a plain clutch plate welded to the clutch basket:"

Looks like a clutch basket to me as there is no teeth on the "...plain clutch plate welded..." you show in your picture.

Click to expand...

So it appears to be a standard clutch basket? With the 3 big plug welds ground down in a very sloppy way?

needing said:

Love the big stabilising washer under the clutch centre nut.

Click to expand...

There seems to be a fair bit of non-standard bits on this rig!

needing said:

By the way, were the clutch plates oily when you removed them?
Ta.

Click to expand...

The friction plates were saturated with oil! The bike leaked like a sieve when running. I took the left side cover off without first removing the drain plug but I'm assuming it was over filled. Could over filling make the clutch behave that badly? What do you think of using Dextron ATF when I put it back together, so I can easily tell if the oil leak is coming from the primary or from the engine?

The friction discs/steels will always be oil saturated since there is oil in the chain case being tossed around by the chain (as it should be). It has never had any ill affect that I can tell on a properly set up clutch...which will be an easy two finger (or less) pull. Oil on the plates will not cause them to slip; improper clutch adjustment or worn out plates will.

ATF is fine in the primary chain case and is commonly used there.

Hi Strong Bad.
1. "Sloppy" welds are better than loose rivets.
2. "Non-standard" could be the previous owner questioned slavish imitation.
3. Therein lies your original complaint - oil on clutch plates. My improvement suggestion is to install a clutch pushrod o-ring assembly (stops gearbox oil getting on clutchplates) and to use 300ml of ATF "Type F - the non-slippy one" (not any of the Dexrons) in the primary cases. If you had oil/fluid in the primary cases then it hadn't 'leaked' out (unless it was being topped up by a leaking LH crankshaft seal).
Ta.

Why yes it is, should I relieve the tension on it?

Click to expand...

not now

you relieve the tension when you have everything in place right after you install the large cir clip

Again thanks for the replies!

IF the clutch basket is a stock basket without an additional "backing plate", with the thinner than expected pressure plate, the clutch should have never engaged or it should have slipped like crazy, right?

I'm slowly trying to get my head around the "dry clutch by design set in an enclosure with oil flinging around to lubricate chain & gears" deal. In my mind one sould expect the friction plates to be saturated. I'm not so interested in the oil on the friction plate issue (which seems like it is a hot button topic here), I'm concerned with the physical set up of having the right bits in their proper place.

Hi Strong Bad.
I took the above picture 30 seconds before I fitted the spring and retainer. The stack height is visible at basket edge and was achieved with an extra steel plate in first. Next time the clutch is apart the steel plate will go in last. This evens the notching wear on the clutch basket and clutch centre teeth. This stack provides full spring compression of plates for maximum power transmission.
ATF = automatic transmission FLUID. It is not called 'oil' even though the Dexrons have 'slippery' additives added. ATF Type F at 300ml bathes the chain, mist lubricates the bearing but does not cause the plates to stick/slip.
Ta.

Just some notes from my experience with a 69 clutch. I'm using the original postage stamp plates and steel disks, all original setup. I find the adjustment screw, the one under the inspection hole, very critical to set up, maybe 1/8 turn tight. I've tried adding another blank plate to take up some of the slop and lower the pressure on the plate, but no matter what ever thickness (even the thinnest barnett plain plate) will make the clutch a 1 or 2 finger pull, but now the clutch slips, so I stick with what I have. The lever pull when adjusted right will 'break over', not unlike a compound bow, so the clutch is not a 2 finger pull, but is a 1 finger hold. I did install the dynodave seal and it was a very close fit. Just for notes, all my plates, rods and measurements agree completely with the numbers I got with the dynodave sheet with the clutch seal and his clutch site.

I'm still using the recommended SAE50 for the triplex chain, so I can't speak to ATF or other fluids, but I do pull the clutch apart once in a while and clean the plates. The only thing I find that makes the clutch hard to use is not set up right or worse yet, a too tight triplex chain. The primary chain adjustment is critical to a correctly operating clutch. The early riders handbook has a very detailed section on setting up the clutch adjustment and the primary adjustment.

I've heard the teflon lined venhill cables make a big difference too (and correct cable alignment), but I don't use them, yet.

Is it ok to run the ATF type F in MK 3 primary with the roller bearing and sprag?

The idea that Norton used a "dry clutch" without realizing that it would get oil on/in it when installed in the chaincase is absurd.

The Norton clutch looks pretty much like any motorcycle wet clutch...or the clutch set in a car's automatic transmission. Wonder if car makers thought the auto-tranny clutch packs would remain dry?

mike996 said:

The idea that Norton used a "dry clutch" without realizing that it would get oil on/in it when installed in the chaincase is absurd.

The Norton clutch looks pretty much like any motorcycle wet clutch...or the clutch set in a car's automatic transmission. Wonder if car makers thought the auto-tranny clutch packs would remain dry?

Click to expand...

There is wet clutch, submerged in oil, and semi-wet clutch like the Norton where it gets splashed with oil and the dry clutch like those of us with belt drives enjoy. :mrgreen:

I was told many years ago that the oil that made it's way onto the clutch plates would be slung off in operation, but I couldn't get the all-metal clutch to not slip, especially when the engine got "on the pipe" There always seems to be a bit of oil in there no matter what, so I have switched the metal friction plates for Barnett fiber plates. I would think the all-metal clutch would have to remain perfectly dry to function well, but others have said not.

some people have issues with ATF and the so called hydraulic tensioner not working.

Mr.Sparks said:

Is it ok to run the ATF type F in MK 3 primary with the roller bearing and sprag?

Click to expand...

needing said:

Hi Strong Bad.
I took the above picture 30 seconds before I fitted the spring and retainer. The stack height is visible at basket edge and was achieved with an extra steel plate in first.

Click to expand...

Based on what you've said, I "dry fit" the clutch stack back in the Clutch Basket and came up with pretty much the same as your pic shows:



So I'm left to assume (yeah, yeah, I know, an ass out of u and me) that there is a plate welded onto the clutch basket making up for the reduced thickness of the pressure plate. Based on this I will re-assemble and give it a try.

Hi Strong Bad.
Looking good. Now to see if function is improved until oil gets on plates again.


Hi mike996. Re:

mike996 said:

The idea that Norton used a "dry clutch" without realizing that it would get oil on/in it when installed in the chaincase is absurd.

The Norton clutch looks pretty much like any motorcycle wet clutch...or the clutch set in a car's automatic transmission. Wonder if car makers thought the auto-tranny clutch packs would remain dry?

Click to expand...

Wet clutch??? Wasn't in 1973 and still isn't / shouldn't be!
This is why ATFluid Type F is superior to Oil in chain drives and why belt drives run Dry (as designed).
Ta.

Danno said:

I was told many years ago that the oil that made it's way onto the clutch plates would be slung off in operation, but I couldn't get the all-metal clutch to not slip, especially when the engine got "on the pipe"

Click to expand...

My hunch is that it depends on exactly what oil is on the clutch pack; 50wt/ATF from the chain case or hypoid EP (extreme pressure) leaking through from the gear box. Regardless, Barnett stlye plates is the fix for the marginal clutch.