Which Belt Drive?

Hi Folks,

I am moving forward on updating my '72 750. Pretty much have the engine mod's decided upon, but now I am looking at belt drive. Not sure I am going to go this route, but am seriously thinking about it. I haven't been able to find any recent threads on belt drive choices, so I thought I would start a new thread.

This is a street only bike, but will have a Web cam 12a (or similar), head work, 10.0 - 1 compression, dual Amals, etc.

I would appreciate any opinions, feedback, criticisms, etc. on the different brands of belt drives. Is there one that is more popular than others? I am not necessarily looking for the cheapest, but prefer a higher quality product. I don't have money growing on a tree in the backyard, but I prefer to spend money upfront on a quality product. Prices seem to range from $300 ish to $950 for a Bob Newby...

Thanks much!

I have no experience with them, but I've read that lots of folks say the Maney one is superior to many of the other ones out there.

I was going to get one but Maney is insane with his shipping prices... He wants $125.00 to ship from the UK to USA. -Is it just me... or it that rather high? Should be no more than $30 or $40.

Maney belts should be the business. Norvil belt kits seem good too, a lot of folk use them, its whats on mine too.

I have a Norvil type on my 850 which I think are made by Pete Lovell. It is well made & has never given me a moments trouble. My 750 has a Maney which is like all Steves parts. Very well thought out & made. It has a steel back plate to hold the bearing. Not sure this is necessary but it's a nice touch. If you like the diaphragm clutch either of these would be fine.
I also have a Bob Newby set up on a Matchless twin. Again, a nicely made piece of kit, with the feel of a six spring clutch which some prefer. HTH.
Martyn.

past Peel had Kenny Dreer sold Haywood 30mm drive that got tested severely with loss of belts and crank and clutch nuts getting under belt to put holes in belt and chips in pulley teeth but new belt, rat tail file and renewed AMC bushes got us back in business no more problemo's. Most belt 1's are higher ratio that chain so expect a bit longer legged feel and better acceleration d/t less spun mass and able to stay in lower gear faster. The belt profile matters HDR vs AT10 or what ever labeled. Either should be ok on street bike but one is weaker than the other if ya look into it.

Crazy Combat runs the R.G.M. item with no complaints from here.

Maney has figured out a way to fit alternator under 1' cover with his 40 mm drive.
We are in 2nd golden age of Commando choices the next generation may not enjoy.

Maney
Next question

Good thread and question. So far, Maney and Norvil seem to be the winners.

A further related question if I may....

My Combat has a 19 tooth sprocket. I am thinking about changing 20 or 21.
I also currently have a original chain primary.
Can I get taller gearing by specifying primary drive tooth option on a belt drive? (not even sure how to word this)
If so, is there a downside to raising the overall gearing one way vs. the other?

Just finished changing the sprocket back to 19 T from 20 with the R.G.M. Have n't tried it yet.

tomspro said:

My Combat has a 19 tooth sprocket. I am thinking about changing 20 or 21.
I also currently have a original chain primary.
Can I get taller gearing by specifying primary drive tooth option on a belt drive? (not even sure how to word this)
If so, is there a downside to raising the overall gearing one way vs. the other?

Click to expand...

Maney's belt drive increases the primary ratio to 1.842, up from the stock ratio of 2.19.
This calculates to just slightly higher than 2 teeth on the countershaft sprocket.
Speeding up the primary reduces shock to the fragile gearboxes, so this can be a good move for some.


So, if one is running a 21 tooth countershaft sprocket on a stock Commando. The ratios are:

2.19 primary ratio
2.0 final drive ratio
= 4.19 overall ratio

With the Maney setup one would have
1.842 Primary Ratio
2.0 Final drive ratio
= 3.842 overall ratio

To get back close to the 4.19 ratio with a Maney belt drive one could use a 19t countershaft, which would give:
1.842 Primary Ratio
2.210 Final Drive Rato
=4.052 overall (slightly taller than a stock bike with a 21t sprocket)

I believe countershaft sprockets are available down to 17 teeth, so you'll be able to find your perfect ratio.

HTH

Torontonian said:

Just finished changing the sprocket back to 19 T from 20 with the R.G.M. Have n't tried it yet.

Click to expand...

Here is a rough idea. These number are not perfect but they are close.
RGM 28 crank 55 clutch 1.965 to 1
100mph = 7000rpm in 3rd,
119mph = 7000rpm in 4th,
55mph = 3750rpm in 3rd,
70mph = 4200rpm in 4th
80mph = 4750rpm in 4th
90mph = 5500rpm in 4th

Hm, Peel's 40 mm Maney kit has 36 crank teeth and 72 basket count so 2:1. If Maney don't offer other T counts they sell various size pulley blanks in logs ya just slice off needed thickness the machine hub taper and side plate screw holes and key slot. Ah if we had the sensations of Kenny snicking next gear and pulling just as hard till scary.

Kenny I need your snail mail to get tires in the works.
hobot@madisoncounty.net.

https://www.google.com/#q=tooth+drive+pulley+blanks

I have a Norvil belt drive on my 71. Runs great, easy install. I would recommend installing Dave Comeau,s clutch rod oil seal mod to the transmission mainshaft. Prevents gearbox oil from migrating down the clutch rod and into your primary. I think you can order one through his website Atlantic green .com. Craig

Here's a plot of theoretical bike speed over a range of engine rpm for a stock Commando (26T engine, 57T clutch and 42 T rear wheel) with various countershaft sprockets.

A friend has purchased 3 of the belt drives from Clubman Racing and thus far is pleased with them. I don't know who's they are, possibly one of the vendors already mentioned, or maybe their own. In Clubman's literature they note that the primary ratio is increased ~ 11% using their belt drive. I presume all the vendors increase the primary ratio because they want to maximize the radius of the engine pulley which in turn maximizes belt survival?

Nobody mentioned Norman White or Mick Hemmings.

I opted for Norman's made to measure complete package, not much more expensive overall, in 35/65 with a 40mm belt, all smaller and lighter than Commando based options, and the choices helped in getting the belt short enough to make me happy, if not Norman. Norman prefers to fit to the bike and be sure it is all set up correctly and adheres to his published price for that service, the extra money I spent got me extras like an inner and outer belt cover which was made to allow for my crank triggered ignition.

Clutch is basically AJS Stormer as used by the works Nortons! (I have 19 and 20 Countershaft sprockets and 40, 42, 44, 46, 48 and 50 rears, I hope to find something that works at most tracks! and will probably find in the end that 20/46 does most things)

I think if I had decided to go with a more do it yourself solution I would have chosen Steve Maney's though I was also interested in Bob Newby's 6 spring clutch.

Mick's offering seems fine and has a good reputation. Some users have found poor adherence to tolerances with RGM clutch centres.

One thing to remember with Steve Maney's product versus say Mick Hemmings/Norman White, Mick and Norman supply a complete clutch with centre, diaphragm and plates. Steve supplies drum, pulley and belt, which is fine and fairly economic if you already have everything else in good condition, less helpful if like me you had no donor parts and would still have had to go to Andover Norton, Mick or Norman or RGM etc. to get the diaphragm, circlip, centre, nut, adjuster and nut and steel and friction plates, with additional shipping costs etc.

On the point of shipping to the US, no I don't think $30 to $40 is reasonable considering some level of insurance and a good delivery time, but $125 or £75, does seem on the high side, I would have guessed $85 or £50, but we are talking shipment from darkest Yorkshire ;-)

Hi Squarehead!
My 2 cents……I got the RGM beltdrive kit for several years without any problems.

I ride my bike several thousand km a year and i tread my commando like a modern bike
...cruising speed beetween 80-90mls on motorways and many load changes in the curvy mountain roads which we got here around in Austria and in our neighbour countries…..
I also ride in real hot climate when I am on motorbike vacation in summer in Croatia, Italy or in the Alps.
And no! ………my primary isnt opened.

I think 30mm is wide enough for the power of a Commando [got a Combat with 10.5:1, much headwork done, Mikuni RS with acceleration pump,…]
….wider belts increase the load on the mainshaft.

The RGM kit is not expensive and another good thing:
you can get the AT10 polyurethan belt in any shop for construction machines for about 20euros [about 30 USD…..and you`ll get the belt for sure cheaper in the US than here in Europe!].

Also when some oil gets from the crank to the primary: no effect on the AT10 belt!
Got experience with another belt contruction on a BSA Rocket Goldstar replica: contact with oil - belt became soft, swelled and finally the teeth rubbed off.

have a nice day! chris

.....i forgot: I would advise you to fit a double sided primary chain tensioner when you go for a belt drive....it isn`t that expensive and is good stuff!

A fit for life and forget Merc "big pin" duplex chain at £55 seems a simple
option post is about £20 to USA.

Andy

PS Thanks for those who have taken the option

WZ507 said:

Here's a plot of theoretical bike speed over a range of engine rpm for a stock Commando (26T engine, 57T clutch and 42 T rear wheel) with various countershaft sprockets.

A friend has purchased 3 of the belt drives from Clubman Racing and thus far is pleased with them. I don't know who's they are, possibly one of the vendors already mentioned, or maybe their own. In Clubman's literature they note that the primary ratio is increased ~ 11% using their belt drive. I presume all the vendors increase the primary ratio because they want to maximize the radius of the engine pulley which in turn maximizes belt survival?

Click to expand...

I have a '74 Roadster with the 19 tooth counter shaft sprocket. It has tons of torque and I find myself in 4th gear
quite a lot. I'm old and usually ride local twisty roads in the 45-65 MPH range. I don't do freeway driving. I'm not
a racer. I'm thinking of installing a 20 or 21 tooth sprocket and would like the opinions of persons who have tried
different sprockets 19-21 and how they worked out in real life. I'm thinking of getting the new electric start from
CnW which comes with a belt drive and don't yet know if the belt drive changes the primary gear ratios any.