Help identifing this belt drive kit? And should I just go back to stock triplex chain?

74 Lloydy said:

Hi, just going to hijack this post as it seems most relevant to my current issue, hope that's OK.

I have had pretty much the exact same failure after a full rebuild. I suspect an adjustment/alignment issue was the problem. However, I also damaged my drive pulley with the wires. As far as I can tell my kit is an early RGM one.

My drive pulley is 28T and clutch pulley is 55T, both 10mm pitch. The drive pulley is 32mm width. The only RGM one that lines up is shown as for racing singles. The new version from RGM that I can see best matches is the "alternator twin" being 27T and 30mm.

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Question is, have I assumed correctly and provided I adjust and shim properly. Will this new 30mm pulley work OK with the original clutch pulley (undamaged) I assume this is 32mm also (I will measure later to confirm).

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You’d be changing the gearing a LOT by doing that.

And how do you know for sure that the clutch drum will be a compatible tooth profile?

Given the relative low cost of a new belt kit vs what you’re gonna spend anyway, I’d strongly suggest buying a new belt kit.

That opens up your choices RGM, Norvil, Steve Maney, cNw all do kits.

A common failure mode with belts is running them too tight. As things heat up they get even tighter till they fail. You really do have to believe and follow the instructions !

When fitting, always turn the engine over a lot to see what the belt is doing. And check it frequently in the first few rides (take the cover off and have a look see).

The debate about double adjusters is inconclusive. I use ‘em, but many run very successfully with a stock single adjuster. So that’s most likely not your root cause here.

Ride a few miles and pull the primary cover. You will be amazed how much the belt can tighten.
One problem I had was clearance for the outside of the belt as it goes round the forward pulley. Had to take some material off the inner
case alternator stud castings, something I was most unhappy to do.
But now nearly 10 years later and nothing has come adrift.
Have often considered a needle bearing idle wheel on the bottom run of the belt to preclude wear when cold and loose. It would only be working
at start up, once hot the belt would be clear of it.
Just a thought.

Seen enough problems with belt drives on this forum. Spend the money and buy a Newby, I have two and never had any problems with belts or clutch! Newby uses a newer and more refined belt design. Instead of square notches that engage sprocket teeth, they are a radius 8mm design that enter the teeth much smoother!

74 Lloydy said:

Hi, just going to hijack this post as it seems most relevant to my current issue, hope that's OK.

I have had pretty much the exact same failure after a full rebuild. I suspect an adjustment/alignment issue was the problem. However, I also damaged my drive pulley with the wires. As far as I can tell my kit is an early RGM one.

My drive pulley is 28T and clutch pulley is 55T, both 10mm pitch. The drive pulley is 32mm width. The only RGM one that lines up is shown as for racing singles. The new version from RGM that I can see best matches is the "alternator twin" being 27T and 30mm.

Question is, have I assumed correctly and provided I adjust and shim properly. Will this new 30mm pulley work OK with the original clutch pulley (undamaged) I assume this is 32mm also (I will measure later to confirm).

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Adjusting the RGM belt is pure luck for me. I never really know if I've got it right. It can run fairly tight when the clutch is fully heated up, but it is one stiff piece of polyurethane and difficult to adjust when cold and check when hot.

I've done a few 150 mile day rides with an RGM belt clutch and I always worry about it approximately the entire time. My worry prevents me from finding out where my Norton engine tops out. Maybe that is a good thing. I never thought twice about failure when I had a single chain clutch in there. Such is life.

If you stick with the RGM, you won't notice that much difference dropping a tooth on the engine pulley. I added one tooth to the engine pulley thinking it would raise the gearing some, and it made almost no difference. It is more important to get your engine shaft and mainshaft shaft centers correct for the chosen belt length then make gearing changes at the gearbox sprocket.

The clutch basket pulley is the same width for all the engine pullies RGM sells. 30mm engine pulley will work with a 30mm belt. It would also work with a 27mm belt, but 30mm is typical for a Commando. I'm using a 25mm belt on a 27mm engine pulley. I have width limitations inside my primary, and that is not an issue with a Commando.

Da truth: If I had a Commando I would not be using an RGM clutch given my experience with an RGM clutch in my pre-Commando. The RGM clutch itself is OK and a big improvement over a 3 spring AMC clutch in pre-Commandos, but I do not like that AT10 belt. That is just me though. One drop in the experience pool.

mean gene said:

Seen enough problems with belt drives on this forum. Spend the money and buy a Newby, I have two and never had any problems with belts or clutch! Newby uses a newer and more refined belt design. Instead of square notches that engage sprocket teeth, they are a radius 8mm design that enter the teeth much smoother!

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Cheers, I ended up ordering a new drive pulley from RGM and a belt. But have also ordered a whole new kit from Steve Maney, which I understand has the 8mm radius design too. I can have a play with both and at the end of the day a spare kit if need be. The 8mm radius design, IMO not being an expert by any means, seems like it must be a better design for this application. Seems like Newby, Maney and CNW ones all run this kind of radius design.

cliffa said:

I may be wrong, but I don’t think that’s a Norvil setup, as the front pulley on mine has no recess.

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Just reading these posts. I had a norvil set up about 20 years ago. It had the recess for the mk3 sprag. After 1 year of telling Mr emery that the tensioning was wrong, 4 different sprocket set ups "at my expense" I was told it would be fine, just go for a drive and all will be fine. After 10 miles the smell of burning rubber and the gear lever jumping about wildly said it all. No apologies, no refund , just a pile of scrap ! The primary was full of shredded rubber wire and even the front pulley was destroyed !!! Norvil F**?wits !

The yaki said:

Just reading these posts. I had a norvil set up about 20 years ago. It had the recess for the mk3 sprag. After 1 year of telling Mr emery that the tensioning was wrong, 4 different sprocket set ups "at my expense" I was told it would be fine, just go for a drive and all will be fine. After 10 miles the smell of burning rubber and the gear lever jumping about wildly said it all. No apologies, no refund , just a pile of scrap ! The primary was full of shredded rubber wire and even the front pulley was destroyed !!! Norvil F**?wits !

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Standard Emery bastardry - and all at no extra cost!

74 Lloydy said:

Cheers, I ended up ordering a new drive pulley from RGM and a belt. But have also ordered a whole new kit from Steve Maney, which I understand has the 8mm radius design too. I can have a play with both and at the end of the day a spare kit if need be. The 8mm radius design, IMO not being an expert by any means, seems like it must be a better design for this application. Seems like Newby, Maney and CNW ones all run this kind of radius design.

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I run an rgm electric start set up with a newer "stronger" belt than the original . They haven't sold one for electric start for a long time now but I believe it's the same ap10 belt set up ? I've only done a thousand or 2 miles on it but as brand new still. Had to get the tension tight ! I look forward to hear about the Maney setup performance. A new one on me! Cheers, Roy.

The yaki said:

I run an rgm electric start set up with a newer "stronger" belt than the original . They haven't sold one for electric start for a long time now but I believe it's the same ap10 belt set up ? I've only done a thousand or 2 miles on it but as brand new still. Had to get the tension tight ! I look forward to hear about the Maney setup performance. A new one on me! Cheers, Roy.

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The Maney kit is probably the most proven out there. Dozens, possible hundreds of race bikes around the world have tested them to the extreme, plus many road riders use them.

They don’t fail unless something else caused it. Period.

The most common reason for failure is probably being run too tight. The correct tension looks very wrong to someone not used to them.

They have the added advantage of raising the primary gearing as well, which takes strain off of the gearbox.

And they’re actually remarkably cheap.

But AFAIK he doesn’t do a mk3 version.

That said, for road use the cNw kit takes some beating. It’s the narrowest belt available I think, which helps makes the installation easier. I’ve been running one a a 920 with 11:1 CR on old and track days for several years now. I’ve never even adjusted it! But once again, no mk3 version.

I ended up fitting the Steve Maney kit, had the RGM one on there and was seeing some odd wear at VERY low mileage about 1/3 in to the belt, like a scored line in the belt and some tooth wear right at the inner side, not bad but was visible. I did leave the rear pulley as is, it was the same as the RGM setup, I did a close inspection and all seemed well there. But something was clearly still not right and I was getting some red "powder" in the case, almost certainly from belt wear. I had it adjusted bang on as per instructions and reading on here, checked hot/cold running all of it and seemed to be running nice and true. I also noticed that the outer "floating" keeper plate with the RGM kit did see an fair bit of wear in the very short duration I had it fitted, was wearing between the pulley and the stator, I had everything torqued up perfectly and all tolerances seemed good, but clearly was seeing some movement, must be from the belt running up against that keeper plate and the fact the keeper plate is free to turn other than being sandwiched between the pulley and the stator. Not going to blame the RGM kit as it could still well and truly been my fitment, but I will say since going to the Maney one it has been bang on perfect (that may be due to both pulleys being replaced now with the Maney kit), the belts are also easier to get locally in Aus for this style kit. Also have to say the Manye kit is nicely done.