Norton Commando 850 clutch plates.

akingg1960 · Jul 18, 2009

Hi

I am in the process of overhauling the clutch on my MK2a Commando.
The workshop manual that I am using says that the friction plates that are fitted to my bike should be between .148" and .142" thick. I have measured them and they are all .125" +/- 1 thou but none of them show any signs of slippage, they are not warped, the internal lugs are still in good condition and the clutch works ?
I have trawled the internet for information but all of the tech spec sites give the same figures.
The plates I have fitted are the original sintered bronze ones.
Do the figures that I have quoted apply to sintered bronze and fibre ?
Any help would be much appreciated.

Regards

Andy KG

L.A.B. · Jul 18, 2009

akingg1960 said:
The workshop manual that I am using says that the friction plates that are fitted to my bike should be between .148" and .142" thick.

The 850 models had 5 bronze friction (and 4 plain) plates, so they are approximately 0.125" thick.
It's the 750 models that had four friction and 3 plain plates, so 750 friction plates are 0.148"- 0.142" thick, the fact that the bronze plates are thinner unfortunately appears to have been overlooked when they printed your manual.

http://www.oldbritts.com/ob_clutch_info.html

http://atlanticgreen.com/ndnsclutch.htm

akingg1960 · Jul 18, 2009

I was at the point where I was considering scrapping these plates so you have saved me the expense of buying a new set.
Many thanks for all of your help - I owe you one !
Regards
Andy KG

ptourin · Jul 18, 2009

If you're rebuilding anyway, you might look into the extra plate modification. It makes the clutch pull much easier - we've done this mod on several bikes and you can really feel the difference. Colorado Norton Works lists a whole kit - look on http://www.coloradonortonworks.com/catalog/drive.asp at the description of item #105. I don't have the details in my head but if this is interesting I can ask at the shop what the mod involves - I believe you just have to install an extra metal plate.

There's a comment about this mod at http://atlanticgreen.com/ndnsclutch.htm - look for "Clutch stack height". Our shop ran into a Norton tech bulletin that suggested the modification.

maylar · Jul 19, 2009

Old Britts sells steel plates ground thinner than stock in .005" steps from .060 to .075. You can buy the set and return the ones you don't need. My clutch dialed in with a .065" extra plate and the difference is amazing.

pelican · Jul 19, 2009

where do you install the plate? All the way at the back? After the pressure plate, or before?

concours · Feb 15, 2012

Resurrecting an old post... I've just dismantled my clutch, sintered bronze plates are all in the .123/.124/.125" range, the steels are all .080" BUT... the steels look like they were NEVER FLAT from new. I can see rub marks on the high spots, but in between, there is evidence the friction plates NEVER contacted those areas. 35 years working in the metal trade, worked with lot's of stamping/punching/finishing operations. It seems to me, there was piss poor manufacturing going on, the plates were not flat from the get-go, and just how much bearing this has on a proper clutch feel, engagement, etc.? EVERY service manual I've ever seen for multi plate clutches mentions the need to evauluate flatness. Has anyone else seen this on the factory steel plates? Are the Barney's any better? Has anyone checked them on a surface plate? :mrgreen:

gtsun · Feb 15, 2012

Hey I don't mean to hijack your thread but concerning "New" barnett friction plates do they need to be presoaked in the chosen fluid before installing?? A friend told me this was important to avoid "Hot spots". Is this a needed step?

Hobot · Feb 15, 2012

Barnett tech support says to wet with ATF then wipe off excess by rag then install to prevent chatter on initial bedding in. Don't put on engine oil and if gearbox oil gets on em don't use solvent that drive oil in pores and leaves a glaze to form, use physical scatch off and detergent then flat plate sand to dry new surface. Stack height is right when diagram spring just exactly barely fits in slot w/o any effort at all. Then measure stack height to know yours for the pressure plate involved.
Al pressure plates available for the anal.

Brooking 850 · Feb 15, 2012

You might want to try this on your sintered bronze plates, that way you can use any weight of oil without slippage

Regards Mike

gtsun · Feb 15, 2012

Thank you Hobot, that seems like good advice.

gtsun · Feb 15, 2012

FWIW, it would be nice if that info & or direction came with the plates. Mine came in the Barnett box from one of our most highly respected parts sellers & I would think that if Barnett suggests pre soaking to be done then directions for this should come with the new plates. Ooops, I wasn't going to hyjack your thread, sorry. About your bronze plates, everything I have learned recently says that plate numbers don't matter, it's getting your stack height right to the spring groove that make the pull nice. As said, read Old Britts on this.

dynodave · Feb 15, 2012

concours said:
Resurrecting an old post... I've just dismantled my clutch, sintered bronze plates are all in the .123/.124/.125" range, the steels are all .080" BUT... the steels look like they were NEVER FLAT from new. I can see rub marks on the high spots, but in between, there is evidence the friction plates NEVER contacted those areas. 35 years working in the metal trade, worked with lot's of stamping/punching/finishing operations. It seems to me, there was piss poor manufacturing going on, the plates were not flat from the get-go, and just how much bearing this has on a proper clutch feel, engagement, etc.? EVERY service manual I've ever seen for multi plate clutches mentions the need to evauluate flatness. Has anyone else seen this on the factory steel plates? Are the Barney's any better? Has anyone checked them on a surface plate? :mrgreen:

Heck even if your plates aren't flat you probably should not blame norton...from the appearance in your pix you may already have barnett clutch plates (.080),
gearbox oil that fouls the plates lets them slip then finally cook and get them blue ++++ warped.
OEM norton and barnett are WORLDS apart ....what norton sells today I do not think is the same despite the claim from the old NA (BSA Regal) that they are made by the original vendor.
I'm not blind yet.... and can clearly see a big difference in manufacturing results.

It might matter for hobot doing 7000 rpm hole shots... but for the street and since a commando is really a touring bike it is rather a moot point even it the plate have been heated a bit.

Clutch tech session on the 3rd saturday starts at 3pm.

concours · Feb 15, 2012

dynodave said:
concours said:

Resurrecting an old post... I've just dismantled my clutch, sintered bronze plates are all in the .123/.124/.125" range, the steels are all .080" BUT... the steels look like they were NEVER FLAT from new. I can see rub marks on the high spots, but in between, there is evidence the friction plates NEVER contacted those areas. 35 years working in the metal trade, worked with lot's of stamping/punching/finishing operations. It seems to me, there was piss poor manufacturing going on, the plates were not flat from the get-go, and just how much bearing this has on a proper clutch feel, engagement, etc.? EVERY service manual I've ever seen for multi plate clutches mentions the need to evauluate flatness. Has anyone else seen this on the factory steel plates? Are the Barney's any better? Has anyone checked them on a surface plate? :mrgreen:

Click to expand...

Heck even if your plates aren't flat you probably should not blame norton...from the appearance in your pix you may already have barnett clutch plates (.080),
gearbox oil that fouls the plates lets them slip then finally cook and get them blue ++++ warped.
OEM norton and barnett are WORLDS apart ....what norton sells today I do not think is the same despite the claim from the old NA (BSA Regal) that they are made by the original vendor.
I'm not blind yet.... and can clearly see a big difference in manufacturing results.

It might matter for hobot doing 7000 rpm hole shots... but for the street and since a commando is really a touring bike it is rather a moot point even it the plate have been heated a bit.

Clutch tech session on the 3rd saturday starts at 3pm.

Worlds apart.. the Barnett being better flatness? These measure .080", Barnetts are sold as .078". The fact that I can see the tumbled finish in the low areas suggest that the adjacent bronze plate NEVER contacted it there.. BTW, the primary was way overfull of GEAR oil, as expected, explains the severe dragging.

concours · Feb 15, 2012

Brooking 850 said:
You might want to try this on your sintered bronze plates, that way you can use any weight of oil without slippage

Regards Mike

Is slippage an issue (when not polluted with gear oil) with the bronze?

Nortiboy · Feb 15, 2012

L.A.B. said:
akingg1960 said:

The workshop manual that I am using says that the friction plates that are fitted to my bike should be between .148" and .142" thick.

Click to expand...

The 850 models had 5 bronze friction (and 4 plain) plates, so they are approximately 0.125" thick.
It's the 750 models that had four friction and 3 plain plates

Gooday LAB,

Some of the last MKV 750s made in 73 (like mine) shared the same 5 plate clutches as the 850.

I guess this is when the 750 and 850 were made at the same time.

Cheers

BillT · Feb 15, 2012

My MkI 850 has the original bronze plates, with no slippage and who knows how many miles. My local Norton guy has seen perfectly usable bronze plates with 200,000 plus miles on them.

My '69 has the atlas clutch. Though it is a much more progressive operation than the Commando, the 850 clutch has had no issues, and seems like a much more robust design.

gtsun · Feb 15, 2012

Hey just a thought: do the guy's running "dry clutches" with a belt etc still "presoak" the plates in ATF or motor oil and then wipe clean even if they will be run dry. ???

Nortiboy · Feb 15, 2012

gtsun said:
Hey just a thought: do the guy's running "dry clutches" with a belt etc still "presoak" the plates in ATF or motor oil and then wipe clean even if they will be run dry. ???

Gooday gtsun,

I run dry with belt, no worries.

I believe the clutch was originally designed to be dry.

It does, in fact run dry. Centrifugal force prevents oil moving inwards. It is usually gearbox oil migrating that is the oil you see.

To answer the thread.

Dynodave easy pull setup and clutch rod seal and I have a two finger, never slip clutch. Standard 850 plates, no worries.

Norton Commando 850 clutch plates.

akingg1960

L.A.B.

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