Belt drive questions (2006)

brittwin said:

Good advice, IMHO. The Norvil belts are of the HTD "Gates" type with round teeth - they run very smooth, but must not be used in an oil bath. There is one kit of 30mm belt width available which allows for retaining the electric starter (sprag) mechanism, but I doubt that occasional greasing thereof will suffice to keep it alive in an otherwise dry primary chaincase. If you want to dispose of the e-start, you may go for one of the pre-Mk.III belt kits (also of 30mm belt width). Their 30mm crankshaft pulleys ensure that the alternat0r rotor doesn't unduly protrude outwards - which is the case with the 40mm belt kit, thus necessitating the removal of the ignition timing indicator segment plate (06-4694) from the inner side of the outer chain case. Is is also a good idea to discard the bronze-type clutch friction plates, and to order a set of "surflex" plates to replace them. And, yes, two additional plain steel plates should come in quite handy - one goes to the backplate of the clutch basket, and an additional one might be needed on the outer (spring) side to get the thinner "surflex" plates packed up tightly.

You'll need a sprocket extractor to take off the original crankshaft sprocket, the clutch compressor tool, and the clutch locking tool. You should also be prepared to find the original crankshaft pulley a tight (taper) fit, secured (against rotation) by a woodruff ("half-moon") key. Heating it up will make this job easier.
Before fitting the new alloy pulley, you'll have to clean the crankshaft taper appropriately of old Loctite residues (solvent, emery cloth). You'll also have to heat up the alloy pulley to approx. 150°C before you tap it home onto the crankshaft taper (w/woodruff key in situ and a little Loctite). The same goes for the fitting of the (sealed) clutch bearing - heat the clutch basket before you tap home the (generously greased) bearing.

To measure the distance between crankshaft and gearbox mainshaft (centre to centre) you don't need to take the primary drive apart. Yes, there are plenty of pulley/clutch basket sizes available, since there's only a choice of two belt sizes (990mm and 920mm). The pulley/clutch basket combo you'll get might thus be not the same as that of the original primary transmission ratio, but you may recitify any such matters by selecting a smaller or larger mainshaft (final drive) sprocket.

Since this is a "first" for you, you'll be able to do it over a weekend - a "pro" could do it within 2 hours. All you'll need to have is the workshop manual(s), the apropriate tools (clutch tool and sprocket pullers are a must!), the belt drive kit fitting instructions, and a little patience. Hope this is of help to you.

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Many thanks. I read somewhere on this forum about a home made clutch tool in stead of having to buy one. Anyone recall this or how I do it?

Can I use any sprocket type puller or do I have use a specific one?

How do I measure the centre to centre distance between crankshaft and gearbox mainshaft without removing the rpimary cover?

I will probably go with the Barnet easy pull clutch option that CNW sells. I took the tranny inpection cover off and the clutch cable is being pulled at the proper angle and nothing looked funny or off to me. I don't really know much about the mechanics of the Commando yet and this is my first venture into doing something myself on it.

Coco
I only have experience of Surflex and std steel plates from UK suppliers. With five steel (one extra steel) and four Surflex and a nylon lined cable the clutch is very light. There is one other way to achieve a one finger clutch and that's to use a Dommie operating arm (coilspring clutch). It gives more leverage but less travel. It's not recommended though it is what I found in my box when I was trying to sort the clutch a few yrs back. I got it to work but getting neutral was often a challenge unless the pushrod play was zero.
For the clutch - eng sprocket centres Norvil have a chart which shows dimensions from 9.134 to 9.433, all the pulley combos and four belt lengths from 880 to 920mm. They measure to 0,4mm (.016") so this needs to be an accurate measurement. I can't insert this so if you want the chart PM me. You have to remove the primary cover, clutch and engine sprocket of course but how you get a truly accurate (to 016") measurement I'm not sure.....a 12" vernier might do it. [/quote]

Keith1069 said:

Coco
I only have experience of Surflex and std steel plates from UK suppliers. With five steel (one extra steel) and four Surflex and a nylon lined cable the clutch is very light. There is one other way to achieve a one finger clutch and that's to use a Dommie operating arm (coilspring clutch). It gives more leverage but less travel. It's not recommended though it is what I found in my box when I was trying to sort the clutch a few yrs back. I got it to work but getting neutral was often a challenge unless the pushrod play was zero.
For the clutch - eng sprocket centres Norvil have a chart which shows dimensions from 9.134 to 9.433, all the pulley combos and four belt lengths from 880 to 920mm. They measure to 0,4mm (.016") so this needs to be an accurate measurement. I can't insert this so if you want the chart PM me. You have to remove the primary cover, clutch and engine sprocket of course but how you get a truly accurate (to 016") measurement I'm not sure.....a 12" vernier might do it.

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[/quote]

Thanks Keith. It seems as though a quick emasurement for the belt drive will not be as easy as I suspected. I gues it is no big deal to have the primary apart for a while as it is winter up here and snowing constantly.

One would assume that a belt kit for a MkIII would be a standard size but I guess that would have been too easy, as nothing I seem to want to do to this machine has an easy solution.

Coco said:

Many thanks. I read somewhere on this forum about a home made clutch tool in stead of having to buy one. Anyone recall this or how I do it?

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You can certainly make a homemade "copy" of the clutch tool - they're simple enough. From the workshop manual / pictorial spare parts & tools booklet you can take the appropriate data. (Can also be viewed on the BSA Regal - Andover Norton web site).

Coco said:

Can I use any sprocket type puller or do I have use a specific one?

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Any sprocket puller of the right size might do the trick, but they require to get the puller legs behind the crankshaft sprocket, which is not easily accessible due to the restricted space - whereas the OEM tool is small and has two bolts which fit snugly into corresponding threads in the sprocket.

Coco said:

How do I measure the centre to centre distance between crankshaft and gearbox mainshaft without removing the rpimary cover?

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Of course you'll have to drain the primary case and then to remove the outer cover to that end.

Coco said:

I will probably go with the Barnet easy pull clutch option that CNW sells. I took the tranny inpection cover off and the clutch cable is being pulled at the proper angle and nothing looked funny or off to me. I don't really know much about the mechanics of the Commando yet and this is my first venture into doing something myself on it.

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Riding a Commando means that you'll have to get used to "venture" into wrench-wielding and dirty fingernails....... If you don't have the right tools to work on the bike, you'll be awfully sorry very soon..... there's nothing worse than missing or inappropriate tools. They exacerbat problems and are no fun whatsoever.
As far as "easy clutches" go, there are no miracles on sale anywhere. The force needed to release the clutch is solely determined by the spring and correct clutch set-up, whereas bad clutch cables / lever angles can add perhaps 5-10%.
If it's not the clutch "pull" that is annoying, but rather it's inability to free the clutch completely when pulled, it is either the clutch bearing gone sticky or, more likely, a worn-out clutch centre. The heavy bronze friction plates tend to bite their (inner) teeth into the often not appropriately hardended centre, and then tend to stick in these grooves.

Coco said:

Keith1069 said:

Coco
I only have experience of Surflex and std steel plates from UK suppliers. With five steel (one extra steel) and four Surflex and a nylon lined cable the clutch is very light. There is one other way to achieve a one finger clutch and that's to use a Dommie operating arm (coilspring clutch). It gives more leverage but less travel. It's not recommended though it is what I found in my box when I was trying to sort the clutch a few yrs back. I got it to work but getting neutral was often a challenge unless the pushrod play was zero.
For the clutch - eng sprocket centres Norvil have a chart which shows dimensions from 9.134 to 9.433, all the pulley combos and four belt lengths from 880 to 920mm. They measure to 0,4mm (.016") so this needs to be an accurate measurement. I can't insert this so if you want the chart PM me. You have to remove the primary cover, clutch and engine sprocket of course but how you get a truly accurate (to 016") measurement I'm not sure.....a 12" vernier might do it.

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Thanks Keith. It seems as though a quick masurement for the belt drive will not be as easy as I suspected. I guess it is no big deal to have the primary apart for a while as it is winter up here and snowing constantly.

One would assume that a belt kit for a MkIII would be a standard size but I guess that would have been too easy, as nothing I seem to want to do to this machine has an easy solution.[/quote]

[quote="brittwin] Riding a Commando means that you'll have to get used to "venture" into wrench-wielding and dirty fingernails....... If you don't have the right tools to work on the bike, you'll be awfully sorry very soon..... there's nothing worse than missing or inappropriate tools. They exacerbat problems and are no fun whatsoever.
As far as "easy clutches" go, there are no miracles on sale anywhere. The force needed to release the clutch is solely determined by the spring and correct clutch set-up, whereas bad clutch cables / lever angles can add perhaps 5-10%.
If it's not the clutch "pull" that is annoying, but rather it's inability to free the clutch completely when pulled, it is either the clutch bearing gone sticky or, more likely, a worn-out clutch centre. The heavy bronze friction plates tend to bite their (inner) teeth into the often not appropriately hardended centre, and then tend to stick in these grooves.[/quote]

I realize the proper tools make the difference. I was a bicycle tech for many years and always had very specialized tools to do certain jobs on certain manufacturers bicycles.

I was told to stay away from thicker aluminum pressure plates as they can get carved up and stick with hardened steel centre. I will order a few tools and start ripping everything apart asap. Thanks.

Coco said:

I realize the proper tools make the difference. I was a bicycle tech for many years and always had very specialized tools to do certain jobs on certain manufacturers bicycles.

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Be prepared to find out that the semblance of bicycles and Commandoes is a rather fleeting one.....

Coco said:

I was told to stay away from thicker aluminum pressure plates as they can get carved up and stick with hardened steel centre. I will order a few tools and start ripping everything apart asap. Thanks.

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There is only one (thick) "pressure plate" in a Commando clutch - that's the outer one facing the spring, it has a prominent pressure ring and it's theeth engage in the clutch basket, not the centre. Instead of a more expensive "thick pressure plate" you can use an additional steel plate which does effectively the same - it makes the dics stack higher.

My first Commando had an awfullly "heavy" clutch - the previous owner had fitted a special, harder diaphragm spring for Norton-engined WASP motocross sidecar outfits, because of permanent "clutch slip" (his statement). I replaced it with a new (normal) clutch spring, replaced the worn-out clutch centre, and filled the primary chain case with 200cc of 20W oil instead of the 350cc of 20W40 that were in it previously. That cured the problem. Switching to the belt drive kit after a while was another improvement: no more triplex chain noise, and approx. 10 kgs less weight due to it's lightweight components and the removal of all the heavy e-start stuff.

Coco, please don't take offense at this observation from a seasoned Commando owner but I feel you are making bigger deal about the clutch and primary than needs to.

First of all, a properly set up Commando in STOCK condition is a very a capable machine. Yes, they do respond well to modifications, but there is always an expense and sometimes a trade off.
Got that off my chest.

Part of owning a Commando is getting intimately familiar with the clutch and primary. Just because there is a clutch problem does not nesitate the cost of a new primary. The clutch is easy to access. Simply remove the footpeg, remove the outer cover and there it is. The primary does not need to be touched.
Just so you know, EVERY used Commando I have purchased has had clutch issues. Wrong stack height, wrong plates, wrong pressure plate (there are two, 750 and 850).

If you only own one special tool, it needs to be the clutch compressor tool. You can get hurt messing around with the wrong tool.
Once you get it apart you can determine the problem. You may have 4 plates (750 style) with a thinner 850 pressure plate. This would make it VERY difficult. Maybe not.
Either way, getting the stack height correct is the key.

My humble suggestion would be to correct the clutch before spending alot of money on a belt primary.

Coco,
I've ran an RGM belt on my Mk3 for 13 years, it must have done 40k miles and never needed adjusting for wear or stretch. It's the same belt as fitted to Heywood drives, steel backed and I believe the strongest on the market.
I fitted it like many others to stop clutch slip, and to that ends it failed. The slip and drag is caused by gearbox oil leaking down the clutch push rod. Fit a seal, Norvil do them or make your own, problem solved. The primary ratio on the RGM drive has been changed to speed up the gear box in an attempt to reduce running loads.
Having said all that, I would agree with MichaelB a belt drive is a lot of money to throw at what is in reality a small problem. Fit a seal, a smooth cable, get the stack height right, and you will find the stock primary and clutch are well up to the job, reliable and light in operation.

I have heard one or two horror stories about Norvil belt drives shredding belts, poor quality manufacture. This is only second hand information, but I use Hayward belt drive running in ATF, belt is very strong polypropylene steel braced, comes with alloy clutch drum & works great

What are the advantages of a belt drive primary?
The chain/oil bath setup seems to be low maintenance and nearly trouble free. Also, it is my understanding that nothing has ever equalled a chain for efficiency in transmitting power. By that I mean the power loss is less than for either belts or gears. Are people converting to belt drives just for the appearance? What am I missing?

I suspect that the main advantage is on the track where the weight saving and ability to run "dry" are useful.

They can be lighter and they give the opportunity to change gearing and thus speed up the gearbox. A lighter clutch assembly is also beneficial for the box.

A belt is quieter and smoother than a badly set up chain. (Badly set up belts don't last very long)

I have only ever come across one case of a Commando triplex chain breaking on the road but have seen and heard of dozens of stripped belts. I suspect that belt conversions are actually a solution looking for a problem I can't really think of a good reason to change on a standard road bike.

A bit like the spoiler on my wife's Contour, it came from racing but for a road car at normal road speeds all it does is add a "look" , which is not completely unimportant, the looks of the bike are a big deal to me too.
I would tend to shy away from changing anything that is as proven as the triplex/oil bath primary chain though, and the stock look of the primary is very nice.
With the belt drive one can have holes in the primary case to show the belt and look just like a racer, but at 58 engine HP I would prefer to aviod anything that might steal even a tiny bit of output to the rear wheel.

The weight savings might be the main advantage then, and might make up for the fractional loss of hp with a belt.

worntorn said:

What are the advantages of a belt drive primary?
The chain/oil bath setup seems to be low maintenance and nearly trouble free.

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'worntorn'
I am afraid this is not so because of several reasons:

1. the Commando clutch is a "dry" clutch running in an oil bath, a contradiction that ensures that the oil will find it's way into the clutch basketand between the plates, thus causing clutch slip. This necessitates additional maintenance work, that is to say, to disassemble and clean the clutch at least every, say 3,000 mls.

2. the primary chain tensioner is nothing but a sick technical joke that doesn't deserve the term "hydraulic" at all - it's a device that collects oil spray and keeps more or less oil in a piston supported by a backpressure valve. If this device isn't inspected and cleaned every 3,000 mls the primary chain tension slackens, the primary drive train vibrates and becomes noisy.

3. Everything under 2 and 3 happens also if you use 200cc of 20W oil or ATF as an oil bath - the thinner oil also renders the "hydraulic" chain tensioner even more useless.

worntorn said:

Also, it is my understanding that nothing has ever equalled a chain for efficiency in transmitting power. By that I mean the power loss is less than for either belts or gears.

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Simply not true, except price-wise. Chains represent the cheapest means of transmission, but definitely not the best. A belt drive - having more and finer theeth - runs smoother, quieter, and practically 100% free of wear if appropriately set up. In addition, it is considerably lighter than a triplex chain, and provides a bit more elasticity, making the life of the gearboxes' innards easier. It is not only maintenance-free, but running it dry also 100% eradicates the oily mess of opening the primary chain case, eg for replacing clutch plates or the final drive sprocket.

worntorn said:

Are people converting to belt drives just for the appearance? What am I missing?

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A primary belt drive is simply better than the triplex chain - in many respects, as stated above. There's not much "appearance" to belt drives, with the primary case closed you don't see that there's one in it....

brittwin said:

the Commando clutch is a "dry" clutch running in an oil bath, a contradiction that ensures that the oil will find it's way into the clutch basketand between the plates, thus causing clutch slip. This necessitates additional maintenance work, that is to say, to disassemble and clean the clutch at least every, say 3,000 mls.

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As the Commando clutch is a completely 'open' design I fail to see how primary oil would not contaminate the plates in a very short time (maybe a minute or so?) under normal running conditions. Although I agree that to run the clutch *plates* dry would be more ideal, many Commando clutches appear to work effectively once it has spun the *excess* oil from the plates. The bronze 850 type plates do need to be cleaned periodically but is this the result of the presence of primary oil? Or because of the burnishing process of two sets of metal plates (bronze/steel) constantly working against each other?
Slip/drag problems at times more likely being caused by gearbox oil contamination from gear oil finding its way into the clutch through the clutch pushrod tunnel and there is a modification available to stop this happening.

the primary chain tensioner is nothing but a sick technical joke that doesn't deserve the term "hydraulic" at all - it's a device that collects oil spray and keeps more or less oil in a piston supported by a backpressure valve.

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Possibly some members here may be unaware that the hydraulic tensioner only applies to 850 MkIII models. I must admit I hear of considerably more belt failures than chain failures although the damage resulting from a belt failure is likely to be considerably less (provided of course that it does not occur at an inopportune moment!!).

I just haven't had any trouble with the clutch or primary on my MK111. My Commando has 26,000 miles on it, only about 7,000 done by me, however I have an excellent set of service records that came with the bike. The service records show nothing being done in that area other than oil changes.

The appearance dif I metioned is in reference to the belt drive converted bikes with cutaway primary cases, not possible with the wet run chain.

I am finding some comparisons of belt vs chain power losses on the net, most claim the chain to be more efficient, but one from the Gates Rubber company claims that certain belts can be more efficient than certain chains. They might be a bit biased however.
I also learned that Buell uses belt final drives on some of it's roadbikes, but converts these to chain on their racebikes. This could be for increased efficiency of transmission, or it could be that the chain has a lot higher tensile strength and can handle the power better.

L.A.B. said:

As the Commando clutch is a completely 'open' design I fail to see how primary oil would not contaminate the plates in a very short time (maybe a minute or so?) under normal running conditions.

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L.A.B.,
the clutch isn't an "open" design, the only way the oil can escape from the clutch basket is through the openings in the diaprhragm spring.

L.A.B. said:

Although I agree that to run the clutch *plates* dry would be more ideal, many Commando clutches appear to work effectively once it has spun the *excess* oil from the plates.

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Once the oil has - more or less - spun from the plates (centrifugal force) it stays in the inner teeth area of the basket, and the spring circlip prevents quite effectively that it escapes completely. In due course, the clutch plates always remain "wet".

L.A.B. said:

The bronze 850 type plates do need to be cleaned periodically but is this the result of the presence of primary oil? Or because of the burnishing process of two sets of metal plates (bronze/steel) constantly working against each other?

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The bronze plates get literally "soaked" with oil and need frequent cleaning, but that applies other friction plate types too.

L.A.B. said:

Slip/drag problems at times more likely being caused by gearbox oil contamination from gear oil finding its way into the clutch through the clutch pushrod tunnel and there is a modification available to stop this happening.

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Yes, gearbox oil creeping along the pushrod tunnel can exacerbate the problem considerably.

L.A.B. said:

Possibly some members here may be unaware that the hydraulic tensioner only applies to 850 MkIII models.

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Yes, but it is a must in Mk.III's - since one cannot adjust chain tension by moving the gearbox towards the rear end.

L.A.B. said:

I must admit I hear of considerably more belt failures than chain failures although the damage resulting from a belt failure is likely to be considerably less (provided of course that it does not occur at an inopportune moment!!).

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If crankshaft pulley and clutch (gearbox mainshaft) aren't perfectly aligned, the result is premature wear and possible damage - to chains or belts likewise. A belt drive is trouble-free, but only if it is one of good quality, and appropriately installed (not overly tight or slack).

On the issue of clutch drag, mine did drag a bit when I first brought the bike home. This made it hard to find neutral most of the time and when cold it would sometimes only partially go into 1st gear, then pop out when starting off. On the advice of the owner of British/Italian motorcycles, I switched the primary oil to ATF. This did not help. A couple of months later I met a member of the local Norton club. He mentioned that the Norton clutch works best with type F ATF. I had been using Mercon. I made the change , expecting no improvement. I was amazed when the clutch drag disappeared within fifty or so miles of running the type F. Now I can find neutral with ease and it goes fully into gear every time.

I don't doubt the belt drives work fine, although the Harley people say that alignment is more critical with a belt than chain, perhaps this is why one hears of more broken belts than chains.

I just do not see a good reason to change something that works well.
On the Norvil site, Val Emery talks about the belt primary conversion on her 650SS. She likes it because it cannot leak oil, which may be the best argument yet for a belt, although my 850 primary does not leak oil, so no benefit there at the moment.

Hi to all.

I started this thread originally and now have some more information to add.

I am using a Norvil belt drive because I was given it as a gift. I liked the idea of it because there was one less fluid to worry about, and I'd been told that once it was set up I didn't need to worry about checking tensions...I prefer my bike to be on the road - not awaiting maintenance, if you know what I mean.

A further benefit came to light when I was discussing a gearbox rebuild with Les Emery, over the years the case hardeneing on the gears had broken down, he said that it would not happen with a belt drive fitted because it introduced a bit of 'cush', rather than the 'hammer blow' which the chain primary drive gave.

Anyway, my main problem was that the clutch drum seemed to wobble as it rotated, about 30 thou movement total in and out.

I stripped the thing down and checked the run out between the clutch inner and the clutch outer - 6 thou. So 24 thou was coming from somewhere else.

What I discovered is that by rotating the (mainshaft) circlip and the spacer which fits over it and the clutch inner all relative to each other then the run out can be increased or reduced.

Since all these are new components (and not pattern either) my conclusion is that all commando clutches must wobble! So no tow I am going

By trial and error I have reduced the wobble to 10 thou. So now, I am going to take Les Emerys advice given to me earlier, and not worry about it.

I gave the bike a run out on Boxing Day (to The White Hart at Fifield, a nice Boxing day meeting) and it ran well, with no problems detectable.

Regarding clutch pull, when I got this bike it had a heavy action. Adding the belt drive made no difference 'at the lever' but there was noticably less slip which I put down to the Surflex plates. What did make a big difference was a new nylon lined cable correctly routed. I also greased the lever around the fulcrum at the same time.

Connected to this, I always had difficulty engaging neutral with the engine running, though if I killed the engine it would snick in really easily. I could NEVER get the clutch 'free-play' adjusted right. The last time I tore the box down I dismantled the section which the cable end joins on to... the clutch operating lever, body, roller assembly. A previous owner had used a regular bolt (threaded up to the top) instead of the correct Norton clutch operating screw. The threads had become flattened by the roller and so there was too much slack in the whole assembly. I reasselbled with the correct part, and found that I could get the correct clearance and that I could engage neutral with the engine running. What a difference a 50 pence component can make!

The only other thing I would add is this...the Commando is a rellay easy bike to work on as long as you have the correct tools, they don't cost much money and they will last a lifetime, so go ahead and buy them.

All the best, Alex

brittwin said:

the clutch isn't an "open" design, the only way the oil can escape from the clutch basket is through the openings in the diaprhragm spring.

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1. By 'open' I meant that the clutch is not designed to keep oil out!

brittwin said:

Once the oil has - more or less - spun from the plates (centrifugal force) it stays in the inner teeth area of the basket, and the spring circlip prevents quite effectively that it escapes completely. In due course, the clutch plates always remain "wet".

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Brittwin, if you should actually take the trouble to inspect a clutch you should see that the standard Commando drum actually has HOLES in the outer drum circumference where excess oil can escape from the clutch. Oil is NOT TRAPPED IN THE HOUSING BY THE SPRING!

brittwin said:

The bronze plates get literally "soaked" with oil and need frequent cleaning

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If that truly was the case then the plates would slip as soon as they got oil on them, and I am sure from my own experience and reading about the experiences of others (here and elsewhere) that there are many Commando owners that still have standard clutches fitted and experience no problems (myself included) under normal conditions, but yes I do agree they can benefit from an *ocasional* clean up. Can bronze and steel become 'soaked'? I am not trying to infer that the clutch would not work better dry I am just saying that it does generally work OK as it is.

brittwin said:

Yes, but it is a must in Mk.III's - since one cannot adjust chain tension by moving the gearbox towards the rear end.

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Yes obviously, but from what you originally said you appeared to infer that the hydraulic tensioner was a common fitment to Commandos. I was merely bringing this to the attention of anyone who might have thought that.