Can I run bronze clutch plates dry?

Fast Eddie · Jan 23, 2014

On a 850 MKII with belt drive...?

Or is this a 'no-no'...?

Al-otment · Jan 24, 2014

Yes. Bronze is a good bearing material. As wear only occurs as the plates slip during engaging and disengaging of the clutch then the bronze plates will last well. Essential to check crank drive shaft and gearbox mainshaft are square in two planes especially when fitting a belt.

Nater_Potater · Jan 24, 2014

Fast Eddie said:
On a 850 MKII with belt drive...?

Sure. They were intended to run dry from the beginning. Alas, the bean-counters got involved... Check out http://www.accessnorton.com/rgm-primary-belt-drive-t5098.html, and pay particular attention to Nortonspeed's comments about the starter sprag on the MkIIIs - "Sure you can get MK3 belt kits but don't waste your money on them unless you are not using your electric starter. It simply won't last. The needle bearing and starter sprag on the crankshaft do need oil not only to lubricate but for the starter sprag washing the 'dogbones' preventing them to stick resulting in a slipping sprag." You can get sealed bearings (search the forum) for the clutch hub, but that still leaves you out in the cold for the starter sprag issue. So, in the end, it's not the clutch plates that are the problem. Nathan

Fast Eddie · Jan 24, 2014

Nater_Potater said:
Fast Eddie said:

On a 850 MKII with belt drive...?

Click to expand...

Sure. They were intended to run dry from the beginning. Alas, the bean-counters got involved... Check out http://www.accessnorton.com/rgm-primary-belt-drive-t5098.html, and pay particular attention to Nortonspeed's comments about the starter sprag on the MkIIIs - "Sure you can get MK3 belt kits but don't waste your money on them unless you are not using your electric starter. It simply won't last. The needle bearing and starter sprag on the crankshaft do need oil not only to lubricate but for the starter sprag washing the 'dogbones' preventing them to stick resulting in a slipping sprag." You can get sealed bearings (search the forum) for the clutch hub, but that still leaves you out in the cold for the starter sprag issue. So, in the end, it's not the clutch plates that are the problem. Nathan

Hi Nathan, mines a MKII... So no electric start nonsense to worry about! It also already has a sealed bearing in the clutch, I assume this came with the belt kit when fitted by PO.
I tried Tony Hayward bronze plates once in a Nourish/ Triumph racer (well 2 racers actually) and they didn't last a meeting! I don't know why that happened, but at least the Commando is cool!
Thanks guys.

pete.v · Jan 24, 2014

The clutch center may be your only concern. It needs to be a hard one for the bronze plates.
Otherwise the Barnett sets are much friendlier, tons cheaper and work great.

rvich · Jan 24, 2014

The belt drive kits commonly available are a huge savings in weight over the stock items. It makes sense to me to continue the weight loss program with the clutch plates. Those bronze plates are super heavy at 230 grams each. Barnett are very light (62 grams), Surflex a little less so (170 grams). To date I have not seen a good argument for the extra weight. Some people report the Barnetts are too grabby. I am not sure why they work well for one owner and not the next. Maybe someone else can shed some light on it.

Russ

Hortons Norton · Jan 24, 2014

Could it be they don't put a thin coat of transmission oil on them during assembly?

rvich · Jan 24, 2014

Hortons Norton said:
Could it be they don't put a thin coat of transmission oil on them during assembly?

You could be right. The Barnetts are supposed to be treated with ATF before use as far as I know.

Russ

pete.v · Jan 24, 2014

Hortons Norton said:
Could it be they don't put a thin coat of transmission oil on them during assembly?

I sure as heck don't either. Perfect smooth release. Maybe they grab cause they oil them. I have read many time about people putting a thin coat of oil, tranny fluid and other stuff. All this does is cake up clutch dust and packs into all the separation.

Its like, what is it ,man? Wet or dry? It's dry, dry, dry!

If you get any oil of any kind on the plates at all, hit them with brake cleaner. And don't re oil it. You don't oil your brake shoes or pads, do you? Do you lightly coat the clutch on your old pick up truck with oil?

If the pack height is right, the clutch operation will be righteous. I grant you, it's a little bit of a black art. There is a graph somewhere here that shows the sweet spot at which the diaphragm should live. This is not fuel for an argument. It is simply what I do that works. It's not rocket science but it does take some math, geometry, physics and common sense.

But hell, to each his own. Do what you think is best. I'll see ya at the stop light. I'll be the one jingling. I love that sound.

rvich · Jan 24, 2014

OK, sorry, I stepped into that. I think the confusion comes from the fact that many of Barnetts clutch packs are designed for wet clutch bikes. And as we all know Commandos are a dry clutch. Unless they aren't!

Russ

MikeG · Jan 24, 2014

pete.v said:
Hortons Norton said:

Could it be they don't put a thin coat of transmission oil on them during assembly?

Click to expand...

I sure as heck don't either. Perfect smooth release. Maybe they grab cause they oil them. I have read many time about people putting a thin coat of oil, tranny fluid and other stuff. All this does is cake up clutch dust and packs into all the separation.

Its like, what is it ,man? Wet or dry? It's dry, dry, dry!

If you get any oil of any kind on the plates at all, hit them with brake cleaner. And don't re oil it. You don't oil your brake shoes or pads, do you? Do you lightly coat the clutch on your old pick up truck with oil?

If the pack height is right, the clutch operation will be righteous. I grant you, it's a little bit of a black art. There is a graph somewhere here that shows the sweet spot at which the diaphragm should live. This is not fuel for an argument. It is simply what I do that works. It's not rocket science but it does take some math, geometry, physics and common sense.

But hell, to each his own. Do what you think is best. I'll see ya at the stop light. I'll be the one jingling. I love that sound.

I had my steel plates surface ground to get exact stack height and lightly coated the Barnett plates with ATF. Clutch works like a charm,has for thousands of miles.

rvich · Jan 24, 2014

I hope the original poster can find someone who is running their bronze plates with a belt drive. I hijacked his thread. I suspect the bronze plates would be fine as in theory they were designed for a dry clutch. Never mind the fact that they always had oil on them when you took it apart. But I have not run them with a belt drive and cannot give first hand testimony.

Russ

concours · Jan 24, 2014

OK, here's some worthless conjecture, based on decades of industrial, automotive, motorcycle repair experience. The sintered bronze plates will work fine, no drama. They won't last as long as they were designed to, but it should be a fairly good acceptable life span.

comnoz · Jan 24, 2014

I have used bronze plates in my racebike and streetbike with no problem until I got the horsepower up. Then they wouldn't hold.

The earlier design Barnett plates were black and were very grabby.

The plates that Barnett have sold for Nortons for at least 10 years are a lighter colored compound and are nothing like the older plates.
I have installed them both pre- wetted and dry, right out of the package. Either way seemed to work fine -other than a tenancy to squeal on engagement -wet or dry.

I like to install a bronze plate as the deepest lined plate in the pack. That is the plate that tends to beat up the tabs the worst and a Barnett will fail sooner in that position. I have gotten around 30,000 miles per set that way. Jim

MikeG · Jan 24, 2014

comnoz said:
I have installed them both pre- wetted and dry, right out of the package. Either way seemed to work fine -other than a tenancy to squeal on engagement -wet or dry.

I like to install a bronze plate as the deepest lined plate in the pack. That is the plate that tends to beat up the tabs the worst and a Barnett will fail sooner in that position. I have gotten around 30,000 miles per set that way. Jim

Thanks for that Jim. I've heard that chirp a time or two from mine and wondered what to think of it.

Fast Eddie · Jan 25, 2014

ludwig said:
" Can I run bronze clutch plates dry? "

Shure , but why on earth do you want to do that with a belt drive ?
The only thing good about bronze plates is that they suffer less from oil contamination , and can be cleaned .
One of the biggest advantages of a belt drive is that you can build a much lighter clutch .
The std 850 clutch ,with the extra steel plate that many install for easy operation wheights in at a massive 6 kg ! .
IMO , the best friction plates are the original fibre plates . You only need 4 friction and 3 steel plates .
Narrower steel plates are not only lighter , but can handle more torque .
With a little effort ( narrower basket , narrower , and alloy centre , thinner pressure plate ..) you can get the weight of the complete clutch down to 2.3 - 2.4 kg , a huge weight saving of 3.5 kg , or almost 8 lbs .
Because most of the weight saving is in the outer rim , the kinetic energy of the rotating clutch is greatly reduced .
This is a blessing for your gearbox sprockets .
Also : not all springs are the same : some are stronger than others : mesure the thickness or put them on a scale .
With a dry clutch and narrow steel plates you can use the lightest springs .
I believe the early 750 springs where the lightest .

Narrower clutch centre compared to std :

both scrap ..

Ok Ludwig, you've got my attention... 8lbs weight saving from the end of the mainshaft!

Well, I already have a lighter clutch than stock of course as I've got an alloy basket, looks like I'll have to get hold of some fibre plates to have a loom at them. Being my first foray into Norton-ism... I've never seen any!

Hortons Norton · Jan 25, 2014

Belt Drive Man used to call the clutch basket a flywheel! He also felt as you Ludwig that it was way over built.

Can I run bronze clutch plates dry?

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