MKIII Primary Oil

C

Cheesehead Commando

Joined
Dec 2, 2008
Messages
99
Country flag
Hi All-

I’m getting miles on my newly re-built ‘75 MKIII which included all new e-starter parts, CNW sprague, etc. The parts were installed by a specialty shop who also re-built my ‘74 Commando.

I seem to recall that the MKIII models utilize a different primary lubrication from other Commando models, is this correct? Unfortunately I have started to experience some clutch slippage under moderate throttle, and suspect the source may be the wrong type of oil.

Any feedback is appreciated.
Thanks!
 
Cheesehead Commando said:
I seem to recall that the MKIII models utilize a different primary lubrication from other Commando models, is this correct?
Click to expand...
The Mk3's hydraulic primary chain tensioner usually needs a thicker oil than ATF in order to work properly. I use the handbook recommended 20w/50 oil.
 
Cheesehead Commando said:
Hi All-

I’m getting miles on my newly re-built ‘75 MKIII which included all new e-starter parts, CNW sprague, etc. The parts were installed by a specialty shop who also re-built my ‘74 Commando.

I seem to recall that the MKIII models utilize a different primary lubrication from other Commando models, is this correct? Unfortunately I have started to experience some clutch slippage under moderate throttle, and suspect the source may be the wrong type of oil.

Any feedback is appreciated.
Thanks!
Click to expand...
You need to look elsewhere. The Commando clutch is a dry clutch. There's always a lot of talk about oils and Commando clutches, but unless overfilled, almost no oil gets on the clutch plates. They are squeezed together tightly most of the time, and when you pull the clutch, it is possible for a tiny bit of oil to get on the plates which is squeezed out when you let go.

The clutch adjustment is much more likely or maybe the cable adjustment at the handlebar. It's also possible (though uncommon) for the pressure plate to weaken. It' also possible that the friction plates are simply worn out. Since it is newly rebuilt, I would ask the shop about it
 
I've been using Rotella T4 15W-40. It's a diesel oil and all I had in the shop one day after replacing the sprag. I had always had some clutch sticking with 20-50 MC oils of different manufacture but the sticking clutch plates have stopped. Rotella T4 meets the spec for wet clutches and although the Commando clutch is technically a dry clutch it's in a case with oil being slung everywhere. I have no slippage. Sprag and new related parts have been successful for some time now so I'm sticking with Rotella. I always have plenty in the shop.
 
I use T-6 in mine, mostly because I always have a little left over from oil changes in my other bikes. It works fine.
 
Deets55 said:
I use T-6 in mine, mostly because I always have a little left over from oil changes in my other bikes. It works fine.
Click to expand...
I use 5W / 50 synthetic in my MK 111 primary and motor . Synthetic gear oil too . Synthetic fork oil too . Only because it's cold Canada . Never a clutch slip or any issues . Enjoy .
 
I use a 10w/40 fully synthetic in the primary as it tends to produce less 'burnt oil residue that's like tar' behind the sprag. The sprag and clutch works perfectly so I assume it is OK to use.
 
I've always been interested in the "discussion" re the commando clutch being wet or dry. The multiplate construction of the clutch in the Commando is identical to that of wet clutch in a Honda motorcycle and the same as a dry clutch in a Ducati. IOW, it looks to me like what makes the difference as to whether a bike has a wet or dry clutch is simply whether the manufacturer has designed it to be IN the oil bath or not. Not sure there is any difference in actual construction...

IOW, the Norton clutch is a DRY clutch ... AND/OR ... The Norton clutch is a WET clutch. :)
 
Last edited:
As a regular service item I've pulled dozens of primaries to clean the clutches back in my paid wrenching days. The complaint was that the clutch both slips and drags. I'd cut radial grooves in the bronze plates to throw the oil out of the pack as the Barnett plates do. Not sure that did any good. substituted one or two Barnett plates in the pack and generally experimented around endlessly. We filled the primary with just enough ATF oil so that it wouldn't run out with the bike on the side stand. That helped. What really helped was to fashion a seal to keep trans oil from running along the clutch pushrod into the clutch. One can buy such a seal aftermarket these days.

On MKIIIs the aforementioned seal plus one Barnett plate and type F ATF to keep the chain tensioner happy reduced slippage. Customers who complained about a sharp takup on the clutch got type A ATF. These days the designations are different but there are still grabby and non-grabby ATFs. I use the non-grabby ATF and it doesn't slip till over the ton.
 
MexicoMike said:
I've always been interested in the "discussion" re the commando clutch being wet or dry. The multiplate construction of the clutch in the Commando is identical to that of wet clutch in a Honda motorcycle and the same as a dry clutch in a Ducati. IOW, it looks to me like what makes the difference as to whether a bike has a wet or dry clutch is simply whether the manufacturer has designed it to be IN the oil bath or not. Not sure there is any difference in actual construction...

IOW, the Norton clutch is a DRY clutch ... AND/OR ... The Norton clutch is a WET clutch. :)
Click to expand...
The vintage Jap bikes I've seen have a clutch that is encased in the crankcase, runs in engine oil, and is half or more submerged. They also have more plates, more springs, and a much more open basket. The vintage British bikes have clutches that work fine when used with a belt drive that is completely dry. In most of them, the oil is just high enough in the primary to keep the chain oiled - they are not meant for the plates to be soaked. Also, all friction plates I've seen are not continuous which allows any oil on them to squeeze out quickly. The clutches on British bikes that I've had slip were 99% my fault (bad adjustment) or 1% worn out. If one is sticking, it has always been an adjustment, maintenance, or plain sitting to long issue.

In fact, in a non-MKIII Commando you could leave the oil out of the primary and just change the chain, sprocket, and basket when they wear out!
 
MexicoMike said:
I've always been interested in the "discussion" re the commando clutch being wet or dry. The multiplate construction of the clutch in the Commando is identical to that of wet clutch in a Honda motorcycle and the same as a dry clutch in a Ducati. IOW, it looks to me like what makes the difference as to whether a bike has a wet or dry clutch is simply whether the manufacturer has designed it to be IN the oil bath or not. Not sure there is any difference in actual construction...

IOW, the Norton clutch is a DRY clutch ... AND/OR ... The Norton clutch is a WET clutch. :)
Click to expand...
Yup.
I run mine flooded well above the level plug.
 
concours said:
Yup.
I run mine flooded well above the level plug.
Click to expand...
Why, I run between 5floz to 7floz and have never had any problems with the triplex chain running dry, putting in more primary oil than what is needed to lube the chain, overfilling when not needed, same as folks having GB oil migrating into the primary, they maybe putting too much oil in their gearbox for that to happen, I always measure the amount of oil I put in my primary as well my GB in what the bible (workshop manual) recommends, I been doing it this way for 49+ years of ownership, have never had oil migration from GB to primary, I don't have a clutch rod seal and I am only on my first replacement triplex chain, but I do put grease on the clutch rod when I do primary service, I did go belt drive for 4 years before having belt troubles, trying to run off even with double adjusters, so went back to chain as there is a bit more give using a chain, my next primary chain is going to be a duplex chain from the chain man when the triplex chain needs replacing.
My Norton was an everyday rider for most of my ownership clocking up between 6K to 10k miles a year till being semi-retired in 2013, these days it just used as my fun bike but still get ridden regularly, it's still my Favorite bike to ride, my Thruxton is my regular rider now.
 
ashman said:
Why, I run between 5floz to 7floz and have never had any problems with the triplex chain running dry, putting in more primary oil than what is needed to lube the chain, overfilling when not needed, same as folks having GB oil migrating into the primary, they maybe putting too much oil in their gearbox for that to happen, I always measure the amount of oil I put in my primary as well my GB in what the bible (workshop manual) recommends, I been doing it this way for 49+ years of ownership, have never had oil migration from GB to primary, I don't have a clutch rod seal and I am only on my first replacement triplex chain, but I do put grease on the clutch rod when I do primary service, I did go belt drive for 4 years before having belt troubles, trying to run off even with double adjusters, so went back to chain as there is a bit more give using a chain, my next primary chain is going to be a duplex chain from the chain man when the triplex chain needs replacing.
My Norton was an everyday rider for most of my ownership clocking up between 6K to 10k miles a year till being semi-retired in 2013, these days it just used as my fun bike but still get ridden regularly, it's still my Favorite bike to ride, my Thruxton is my regular rider now.
Click to expand...
Longevity.
Because the Barnett plates like to be bathed in oil.
And it cools the stator.
And it lubes the clutch basket bearing.
 
concours said:
Longevity.
Because the Barnett plates like to be bathed in oil.
And it cools the stator.
And it lubes the clutch basket bearing.
Click to expand...
I still run my original clutch plates even after all these years, still have my original stator but it has had a new centre put in about 35 years ago and I run a sealed clutch basket bearing, my clutch centre and pressure plate is the only thing that has been replaced about 15 years ago, other than that the rest is what came with the Norton from the factory, well the triplex chain was replaced of course, so I think I got longevity out of my primary and gear 49+ years.
 

Similar threads

olympus
Alton Primary Oil Leak... Finally found
Replies
5
Views
860
olympus
olympus
olympus
Primary Oil Leak found
2
Replies
22
Views
1,473
olympus
olympus
T
Primary oil sucked into engine.
Replies
13
Views
1,361
o0norton0o
o0norton0o
akira shimomura
About the primary oil in the Norton Command 750
2 3
Replies
41
Views
3,441
akira shimomura
akira shimomura
Shelby-Right
Home made tools for the BSA , primary OIL leak !
Replies
5
Views
1,023
Shelby-Right
Shelby-Right
Back
Top