Clutch question

I recently purchased a 72 Commando Interstate - runs VERY well, will be correcting and upgrading various issues this winter. Have already changed the engine and primary oil. The clutch exhibits a strange habit of "sticking", for about 1-2 seconds after I pull the clutch lever in. I believe it is correctly adjusted, engages very smoothly, and disengages fully - I can select neutral from 1st of 2nd, quite easily.

The sticking, or delayed disengaging, is very consistent, whether upshifing or downshifting - just takes a second or two until it releases.

I mentioned this over at my local BMW dealer (I ride a K1200LT also) and the service mgr as well as one of the younger mechanics immediately knew what I was talking about. The svc mgr suggested an old cure: Drain the primary case, refill with kerosine, ride a few miles, drain and refill with normal oil. Anyone ever hear of this cure?

Stuart Ostroff, Phila. :?:

Stuarto,

The problem that you are facing is that your clutch is suffering from oil contamination. The clutch is supposed to be dry and oil migrates from the transmission via the clutch pushrod.

I have never done the kerosene in the primary thing, nor do I believe that it would be very effective on a Norton. You would pretty much have to half fill the primary with kerosene to get it where you needed it and then it would probably do more damage than good.

The recommended fix is to disassemble the clutch (you will need a clutch diaphragm compressor tool to perform this job) and clean the clutch plates with brake cleaner, varsol, kerosene, etc. Examine the plates for any warpage, wear, rust, etc. Rusty disks can be saved by bead blasting them, otherwise replacement part should be found. To put an end to this condition once and for all, install one of DynoDave's clutch pushrod seals. They work very well!!

Another cause for a draggy clutch is a worn clutch hub. This typically only happens with bronze clutch plates (yours should be fibre plates, if original) and the symptoms that you list don't really sound like this is your problem. That said, have a good look at your clutch hub as a precution.

While you're in there, examine the clutch centere bearing for excess play by rocking the empty basket back and forth. If the basket moves more than about a 1/16" relative to the hub, replace it.

A couple of more things that have worked well for me:
1. Reseal the primary cover with Permatex #2 gasket eliminator. Follow the instructions on the tube and this should give you a leak-free primary.
2. Refill the primary with 170cc's of ATF. If some does get on the clutch, it won't burn on. (As an aside, with my uncle's MkIII, it actually improved the operation of the starter sprag clutch!)

Hope this helps,

Derek

Stuarto,

Check for excessive wear on the splines of the clutch centre and sprocket. Deep notches in these areas will prevent the clutch from disengaging cleanly.

Also, I recommend a new clutch pack by Barnett. Oil will not harm these Barnett clutches in the least; in fact, I soak them in oil for an hour or so before assembly.

Regards,

Jason

stuarto said:

I recently purchased a 72 Commando Interstate - runs VERY well, will be correcting and upgrading various issues this winter. Have already changed the engine and primary oil. The clutch exhibits a strange habit of "sticking", for about 1-2 seconds after I pull the clutch lever in. I believe it is correctly adjusted, engages very smoothly, and disengages fully - I can select neutral from 1st of 2nd, quite easily.

The sticking, or delayed disengaging, is very consistent, whether upshifing or downshifting - just takes a second or two until it releases.

I mentioned this over at my local BMW dealer (I ride a K1200LT also) and the service mgr as well as one of the younger mechanics immediately knew what I was talking about. The svc mgr suggested an old cure: Drain the primary case, refill with kerosine, ride a few miles, drain and refill with normal oil. Anyone ever hear of this cure?

Stuart Ostroff, Phila. :?:

Click to expand...

What oil are you using in your Primary chain case?

My mechanic/parts supplier recommends SAE 10 non detergent for the primary chain case.
It has worked very well for me over the last 10+ years.

Like Derek, members of the Norton Owners Club recommend using ATF in the priamry chain case.

http://www.nortonownersclub.org/technical/commando/comclutch1.html

With all respect to Derek, I thought the standard Commando clutch was a WET clutch with bronze and steel alternating plates. It is meant to run with oil splashing around inside the chain case.

The above thread also gives suggestions similar to Derek's for keeping Gear Box oil out of the Primary Chain case.

I would suggest using a lighter oil or ATF and keeping an eye on your Gear Box oil level in case you are losing excessive amounts of hypoid 80/90 oil.
If that doesn't help Jason and Derek have good tips to help you resolve your problem.

Good Luck

Wringer, Stuarto, et al,

Yes Wringer, you are correct; the Commando primary is designed to run in oil. I use 20W 50 in my primary with a Barnett clutch and have had excellent results.

Regards,

Jason

Barnett?

My mechanic has been around Commando from the time they were new and just asked for my stock plates to replace the Barnetts I did put in my clutch; his experience with the Barnett showed him that these plates were too "sticky" and he saw a lot of gearboxes breaking on downshifting as the Commando do not have a real transmission shock absorber. Guess there is even less absorbtion with the belt (Norvil) I just installed! Any thoughts?
Philippe

Philippe,

In my opinion, Norton gearboxes just aren't up to the task of transmitting power from a 750cc engne, much less a 850cc engine, to the road.

These gearboxes were originally designed by AMC for installation on 500cc motorcyles. Later it was installed on the 650cc Atlas followed by installation in 1968 on the 750cc Commando. And finally, in a form largely unchanged from its 500cc application, this gearbox was installed in the 850 Commando. In a way, this is quite a testament to the extraordinary strength of the original design. (I'm sure I've left out some history, like the Dominator application, but in general this was the way it was.)

So you see, it's not the clutch, or chain, or belt - but the gearbox that is at fault. Nevertheless, you have to give that old AMC gearbox heaps of credit for hanging in there for as long as it did.