home on a tow truck

Onder said:

Remember that the belt gets a LOT tighter when the bike warms up. I was amazed how much tighter.

I tend to agree about the chain being the long term way to go. But most of us succumb to the 'make-it-better'
syndrome. Belts are lighter, a lot lighter, need no oil.
So my Norton got one. My Enfield Interceptor got one because you cannot source all the clutch bits. My
Trident stays with the chain because of lube issues with the standard clutch.

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I'm not so sure about the long term idea. I have yet to see a Norton primary chain that lasted 70,000 miles, I have a box full of them with cracked rollers and missing side plates .
Of course they are more likely to get you home even with damage.
I also have the remains of a chaincase and engine case that didn't make it home after the chain failed. Jim

Cam belts have been on cars for years now and most don't give problems, unless you own a 2600 rover SD1 where you really have to change the belt every 20,000 miles [ 10 mins work and very small belt ] or a Ferrari where you have to change those every 3 years whether you need to or not. Jap cars say change every 100,000 kms or 60,000 miles. So if ya get 60,000 miles out of a belt ya doing ok. As its not so critical, leave it on till it blows. A cam belt is a different story of course. I did see a Cressida 6 cyl taxi once with a belt that had done 130,000 kms. It looked cooked.
In our case, most of use probably have good working sprockets and clutch hubs, and would rather spend less money on just changing the chain. When our clutch hubs are knackered then we may consider investing in a new belt drive system. Makes sense to do what you need to do, and do what you can afford. Both systems are good ideas and they both work.

Dereck

I had a SAAB 9000 with timing/cam chain, it did 140,000 miles with no signs of wear and on the SAAB forums 200K life was regularly reported.

comnoz said:

kerinorton said:

Haven't had a problem with any of my primary chains, and my 850 might be the most traveled in NZ right now.

Dereck

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I haven't had chain problems either. But I have had problems with oil leaks from the primary... Jim

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And here I thought it was just me. After my second recent primary drive teardown to fix leaks, I now have it down to one leak; the rear case half fixing stud. Hoping I can cure that by just removing the outer and putting a fiber washer on the stud.

Can't say that I see what the relevance is of quoting life and maintenance intervals for "Cam Belts" on automobile engines when discussing "Primary Belt Drives" on Norton motorcycles?

Besides, it's an argument for chains over belts anyhow. Cam chains on cars often go the life of the engine; cam belts have to be changed or they'll break, no small event in an interference engine .....

I think the best answer has already been given. "It's not really better, but it feels like a modern upgrade". I can go along with that.

Lannis

The only thing I found was the clutch basket wobbling, it looked like the clutch nut had backed off and the clutch centre is a sloppy fit on the splines that relies on being pulled up tight by the clutch nut. The clutch house bearing and the main shaft all appear to have no play so I'm going to box it back together and use a better locking tab, the tab I had had ears to bend up around the nut but not one to knock into the holes in the clutch centre, to anchor it as if to say.
When all this was fitted together I was not able to use the clutch spacer that goes over the circlip on the mainshaft, it was slightly too wide to allow the clutch to align. I used a correct size spacer just butted up to the circlip, when I re fit it, would there be a benefit to using a proper circlip as I'm not using the original spacer?? I keep meaning to turn the original spacer to allow it to slip over the clip a spot more and give me my required clearance, but that aint going to happen this time, so original circlip or what I would refer to as the one with ears for pliers, would there be any benefit?

Either, as long as it's new. (the one with ears for pliers is a seeger clip) you could also consider a belville washer to hold your clutch centre on, 40 ft/lbs and some loctite

That wobbling clutch probably wasn't good for the belt. That is a common problem with worn parallel splines in the clutch hub and main shaft. the only splines that will last in a situation like that are the ones that are a very tight fit.
As it is, you need a good high tensile washer under the nut on the clutch hub or you will find you have to frequently tighten that nut because of oscillating wear on the washer [ cause by loose splines ]. my 850 has done heeps of miles and is definitely loose. My 750, which has just done 14,000 miles, is better but still an easy slide fit, so will always tend to wear out the washers either side of the hub.
The only cure is the check the tightness of that nut regularly.


Note here, the factory says the king pin in the swing arm should be a push in fit in the g/box cradle. Yeh right. If king pins on cars or trucks were that easy to fit, they would flog out in no time. [ i have mentioned this because the easy slide fit if the hub on the splines is a similar equation ]

Someone asked about the relevance of comparing cam belts with these drive belts. It was just to suggest the drive belts might last as long as the cam belts so after 60,000 miles you must expect the belt will break or wear out.

I mentioned earlier the taxi with the cooked cam belt which had done 130,000 kms. Jim mentioned his belt did 70,000 miles. Those are similar equations.

Dereck

ps. another comparison. I fitted new front exhausts pipes to my commando before doing the trip round NZ. Why. So i had a good idea they would not break on the trip. Marks 20 year old front pipe broke on the Lewis Pass on the way home. Where do you draw the line?

Lannis said:

kerinorton said:

Haven't had a problem with any of my primary chains, and my 850 might be the most traveled in NZ right now.

Dereck

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I don't understand.

On each of my 4 British bikes, the oil-bath primary chain is the most reliable, maintenance free part of the design.

They seem to last forever, need adjustment seldom, and never fail. I don't have to remove the electric starter to use it, and the oil that helps the chain last also does its job with the clutch and alternator.

From what I can tell, reading about broken belts, stripped teeth, having to remove starters, overheating alternators, etc .... if someone offered to install a belt for me on my MkIII for FREE, parts and labor, I would turn them down, because I can't see at all how it is an upgrade.

Only belt I've ever had was the rear drive belt on my new 1984 HD ElectraGlide. It was OK I suppose but had to be adjusted just like a chain, AND I know that folks would lose the belt if a rock were kicked into it - the big chain on HDs never breaks.

So what am I missing that many other people seem to know?

Lannis

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It all depends on what four British bikes you have and the quality of the primary chain etc if it's a simplex chain on a pre unit triumph or bsa etc then a belt primary would probably be better,as they can snap and they need regular adjustment also they don't lubricate well at high revs,if it's a duplex primary or triplex then the gains of changing to belt become smaller,but what you do gain is a clutch less likely to slip, one less potential oil leak and a much lighter primary drive cheers

I have to agree with the comments that imply that a belt drive on a Commando is a solution for which there is no problem. Re the comment about Ferrari, it is interesting to note that Ferrari, after many years of futzing around with cam belts on their v8's went back to chains. If chain case oil leaks are the concern, there are plenty of good sealants around today that can prevent it. Permatex Moto-Seal a (thankfully) non-silicone sealer, which is essentially their version of Yamabond or Hondabond, can keep a Commando from dripping on the floor! The last time I put ATF in the chain case was when I installed the Alton E start in 2012. None has leaked since thanks to Moto-seal.

OTOH, I do have gear oil seeping from the gearbox via the X-ring seal. Sadly, Moto-seal cant help that.

I've had a belt drive from Norman White on my Commando since some time around 2000 – 2002. I notice it has many more teeth than those of the setup in the photos earlier in this thread, maybe twice as many. I wonder if that makes a difference. The thing for me was, while oil always seemed to get out somewhere – perhaps mainly through the alternator wire grommet – I couldn't seem to get the chain adjusted right. While Norman told me I had it way too tight, there are deep witness marks from the chain to this day on the inside of what was a brand new inner chaincase, fitted by me. That came about through a broken alternator stud mount – I'm not aware of having broken it, I just noticed it one day. I wanted the bike back on the road asap so just ordered a new inner chaincase. You might think that makes me out to be clumsy, but you wouldn't believe how I've fussed over this bike! Anyway, Norman assured me that he knew of one of the belts he uses having covered more than 100,000 miles. While he was at it, I had him spigot the gearbox too for trueness. Who knows, that might've solved the mystery chain issue. I wouldn't dream of suggesting that poor reports for belts are wrong, but I have to say I find the belt setup to be so much easier to work with, and it hasn't given me any trouble yet. Also, from what I've seen and heard, the worst that would probably happen is I lose my drive and need a new belt. I've had a chain break and practically destroy an engine, although not on a Commando, and I was very young, so there may have been an element of youthful ignorance. Then again, that's only over some 20,000 miles or a bit more in my case – for very boring reasons the Commando was in storage between 2005 and earlier this year – and I've only ever ridden it on public roads. Just FWIW.