Could I get a realistic view on belt drive?

Despite years of saying I am not interested at all, I am considering some changes that would include belt drive. It's not the belt drive per se that I'm interested in but it's part of the "kit."

I'll say up front that I have never had any issue at all with the chain primary so I have no complaints about it. For those that have belt drives and switched to them from the OEM chain, do you feel there are clear advantages? If so, what are they? How about any disadvantages?

Thanks for any info.

Bad reviews would save me a bunch of money!

Hi Mike, i will help you sit on the fence.
Have had 2 belt drives, an RGM on my Commando (went back to chain when Alton starter fitted) and a Newby on my ES2.
To me there have been only 2 noticeable advantages - no need to adjust the primary since the belts don't stretch, and no more Norton Patented Oil Leak from the primary (especially on the ES2).
Downside, which hasn't affected me yet touchwood, you do see or hear of a lot more roadside failures to proceed with belts than chains. Perhaps set up, perhaps because belts don't stretch people don't replace them until they fail.
Was the money well spent - ES2 undoubtedly, Commando i am not so convinced.

I have run a belt drive for approximately 20 years never had a problem with it
The advantage for me if you can call it that is the light weight of the whole set up ,plus no oil leaks although I built this bike from parts so I wouldn't know if it ever would have leaked
My other commandos I owned didn't leak
The clutch works superbly running dry ,I use Barnet clutch plates
But I did have to make a seal for the push rod when I saw how much oil was migrating from the gearbox to the primary, I have changed the belt a couple of times but the belts are perfect condition , cheers

I assume you are talking about belt primary drives, not final drives. If so then I would only use the original
chain drives on restorations.

Yes, primary drive.

For me, the big deal is the saving of rotating weight.

Get one with an alloy clutch basket, and use a Barnet clutch pack, and the weight saving on the end of that poor, long suffering, gearbox main shaft is just insane!

If electric start is a current, or future, interest, the cNw offering would be high up on my list.

74 850 have BNR. It is a lot lighter than stock. In service I find it is a bit grabby but it never slips
under power.
I did find that fitting it was a bit of a trial because the back of the belt rubbed on the stator mounting
towers. They were ground down as much as I dared and still there was some rubbing. Some of this is due to the belt being loose at cold start. Once it warms the belt will tighten considerably so you have to have a fairly loose adjustment. I think a proper adjustment thread would be a thread that would out do an oil thread!
Oh and one other thing: I have a small leak at the crank which now that the belt obviates the need for primary lube becomes noticeable. Ive changed seals three times and no joy. PIA but not a show stopper.
So it wasnt entirely plug and play. On the whole, Im still happy with it.

i am with what has been said as to a major weight reduction in the drive and a dry primary. but IMHO the better part is the ability to over drive the primary which in turn allows a smaller countershaft sprocket. this is a win win on the gearbox with less torque going in and better multiplication on the output side. norvil offers several ratios and the RGM is 2-1 with IMHO a better belt but you will need to machine the snap ring groove a little wider but both are a huge weight reduction over stock. the norvil will work with the alton and dont know about the RGM with the alton. in talks with john @ sts i wish he would offer a 2-1 on the CNW kit and i explained my position as to why.

Luckily this has been beaten to death and all of the salient points have been cover in this thread already.

Sadly one of the best kits was the Maney and they aren’t available anymore.

Onder said:

74 850 have BNR. It is a lot lighter than stock. In service I find it is a bit grabby but it never slips
under power.
I did find that fitting it was a bit of a trial because the back of the belt rubbed on the stator mounting
towers. They were ground down as much as I dared and still there was some rubbing. Some of this is due to the belt being loose at cold start. Once it warms the belt will tighten considerably so you have to have a fairly loose adjustment. I think a proper adjustment thread would be a thread that would out do an oil thread!
Oh and one other thing: I have a small leak at the crank which now that the belt obviates the need for primary lube becomes noticeable. Ive changed seals three times and no joy. PIA but not a show stopper.
So it wasnt entirely plug and play. On the whole, Im still happy with it.

Click to expand...

Reed valve on the crankcase? If not, try a seal made of unobtainium.

As much as i like the idea of weight reduction on the mainshaft, i dont think i will use another belt drive. I have an RGM in my 750.

Pros,
Weight reduction
No oil, no oil leak
Quiet

I fitted a 20 tooth countershaft sprocket and it feels like a 22 tooth due to the gearing. Due to the lack of oil, the clutch is grabby and squeaks a little bit when i pull away (got 3,500 miles). Barnett plates.

I like the momentum of the heavier clutch. This winter i will probably go back to chain drive. Or maybe put a 19 tooth countershaft. Have not decided yet,

Cheers

That’s interesting about the clutch being grabby.

2 x Maney belt drives one x 30 mm for the road bike and one x 40 mm for the race bike.
Set and for get for me, did break a belt on the race bike when a stone got under it , during qualifying so had to start down the back of the pack that day.
A racing colleague who builds a Commando for a young hotshot rider expressed his concerns over some of us running belts, "I run a chain as they dont break" famous last words, commentators curse maybe, his rider broke a chain, although we are talking racing, not general road use.
Ease of maintenance, set and forget, weight saver, slightly taller 1st gear with a 21 tooth GB sprocket on the roadbike, no oil leaks and Norton clutch was originally designed as a dry operation unit.
For me, very happy not to be messing with oil and wet slipping clutch and reading on the forum the best oil to use !
Roadbike one had to be shimmed out board slightly on the GB shaft so as not touch the inner primary, but as the clutch basket is plenty wide enough there is no alignment issues with the belt.
If you do go down this path, just make sure your basket and front sprocket/pulley are in exact alignment, I do this with the rotor on the crank, set a steel rule across the two faces of the clutch basket ( without the diaphragm plate) and use the magnet on the rotor to secure the steel rule, then use another shorter rule across the face of the front pulley, then using both GB adjusters set accordingly. Align the two rulers in parallel .The 70 to 90 degree twist on the belt between the basket and the front pulley works for me. It also makes it easy to roll another belt on with undoing the GB and backing off the adjusters. Just whip the stator off and roll another belt on.
I face the RHS GB adjuster forward as on the LHS for ease of adjustment as if in its original position its a pain to get at.
Hope this helps you to make a decision
Regards Mike

Brooking 850 said:

I face the RHS GB adjuster forward as on the LHS for ease of adjustment as if in its original position its a pain to get at.

Click to expand...

Nice trick. It is a PITA.

I have the street version of Steve Maney belt drive system on my 74 Interstate and love it. Light weight and easy on the gearbox. I run the Surflex clutch packs which never slipped. They chirp a bit on takeoff. Gone through two sets. Still on my original belt though I keep a spare. As stated above don't run them too tight. Twin lollypop adjusters are recommended and its a set and forget no nonsense setup. dynodaves main shaft output seal is a must. Over 42000 miles on the belt drive and counting. Never look back.
Cheers,
Thomas

RGM with Surflex and DD seal. 72 model. Really like it.
At my age I can now only drive the 76. The Sprag will not tolerate the dry system.

I also run a Steve Maney (street) belt drive ,and couldn´t be happier.
Quietened down the primary a lot .

MexicoMike said:

Despite years of saying I am not interested at all, I am considering some changes that would include belt drive. It's not the belt drive per se that I'm interested in but it's part of the "kit."

I'll say up front that I have never had any issue at all with the chain primary so I have no complaints about it. For those that have belt drives and switched to them from the OEM chain, do you feel there are clear advantages? If so, what are they? How about any disadvantages?

Thanks for any info.

Bad reviews would save me a bunch of money!

Click to expand...

clear advantages?
Finally found my original reply to this question.
https://www.accessnorton.com/NortonCommando/inner-primary-main-shaft-seal.13680/#post-193739

Not wishing to muddy the waters but I perhaps should have noted that my opinion of the BNR belt drive
is coloured by my having a TTI gearbox. They dont leak oil into the primary cavity. They are a good deal
stronger than the stock box in every way. They shift wonderfully. So just how different the belt and clutch
are from the stock setup is probably a bit hard to tell.
I vote for the belt and the TTI five speed. And to continue aft I like the x-ring chain and the Madass cush drive.
Oh well not much stock left in that area now is there!

Just other little benefits that come to my mind:

you can replace the belt without dismantling the clutch nice and easy.

I got the AT10 belt from RGM and always got a spare belt in my side panel.

AT10 belt is also used in industrial engines and machines….so you get them for less money from any technical distributor.