Questions About Belt Drives

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Bonwit

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The quest for a Commando continues. One bike I'm looking at has had a belt conversion. What I haven't seen before it the holy primary cover. I assume that all the holes drilled in the cover are to allow it to breath, but is this a common feature of this conversion? The owner said he did the conversion himself a number of years ago, but couldn't remember the kit manufacture. Does it have to have this cover? Or is there another alternative that lets you retain the stock cover? He still has the old cover along with all the other parts that came off.

Also, he indicated that with the clutch engaged, there was a slight rattle coming from the clutch plates, supposedly because of all the holes allowing for the mechanical noise to get out. He didn't think it was anything abnormal, just different from the stock arrangement. Does this sound normal?

Thanks
 
I have had a belt primary for 10 years now, I LOVE it.

You do not HAVE to vent the primary cover.
I run with all three primary inspection covers removed all summer, and will put them all back on in November.
The baskets and engine plates heat up and take the slack out of the belt when fully hot.
I ran all summer once with the primary not vented at all, no ill effects.
Is a LEFT side threaded gearbox adjuster installed?
My clutch plates do not rattle at all, maybe you should get in there and look at the condition of everything.
 
there are two if's in your question. first is how heavy is the cover vented? and two is what clutch plates are you running. if you have the 850 style bronze plates than yes you will get clutch rattle and the more the cover is vented the more noticeable it will be. I have a belt drive and DO NOT have a vented primary case so it does not seem to be an issue in 23.000 miles. I also run 5 sureflex plates as it is a LOT lighter clutch than the bronze but it takes a little work to fit 5 of these.
 
highdesert said:
Is a LEFT side threaded gearbox adjuster installed?
Click to expand...

I haven't seen the bike in person yet so I don't know about an adjuster. Is this necessary? What should I look for.

Thanks
 
bill said:
there are two if's in your question. first is how heavy is the cover vented? and two is what clutch plates are you running. if you have the 850 style bronze plates than yes you will get clutch rattle and the more the cover is vented the more noticeable it will be. I have a belt drive and DO NOT have a vented primary case so it does not seem to be an issue in 23.000 miles. I also run 5 sureflex plates as it is a LOT lighter clutch than the bronze but it takes a little work to fit 5 of these.
Click to expand...

Thanks for the reply. Yes, I believe he used the original plates, and it is a '74 850, so I guess that's the source of the rattle. Would the Sureflex plates be "plug and play" and would that take care of the noise? Also, would not having a vented cover be an issue in our 100 degree Texas heat? Are there any other means of venting without having a cover that looks like Swiss cheese?

Thanks again!
 
Gday BONWIT
else where on this forum someone mentioned that they have vent holes drilled on the inside cover and you cant see the swiss cheese effect unless looking hard.In regards to the rattle, it could be a worn clutch centre aswell? With vented covers you have to expect some noise to escape but thats a trade off for cooling. I dont mind a dry clutch rattle, adds a little bit of personal petina, ala Ducati,where even the floating cast brake disc rattles on them. It gives it a mechanical sound. Something that I love but others like theirs to sound like a mothers sowing machine?

Regards FOXY
 
YES, I feel it is very important that a belt primary have a left side threaded gearbox adjuster.
It is more critical for belt to run true than a chain, and a left side adjuster allows one to set belt run truer.
 
Thanks for the reply. Yes, I believe he used the original plates, and it is a '74 850, so I guess that's the source of the rattle. Would the Sureflex plates be "plug and play" and would that take care of the noise? Also, would not having a vented cover be an issue in our 100 degree Texas heat? Are there any other means of venting without having a cover that looks like Swiss cheese?

Thanks again![/quote]

the sureflex plates are .020 thicker than the bronze plates so it is not a plug + play. old britts sells thinner steel plates so you will need to order some of them and play with stack up height using a combo of stock and thinner steels. another benefit with this setup is you will get a 2 finger clutch pull along less weight on the main shaft and less rattle.

the belt in mine has run in Fla heat and has not had an issue. but if you want to vent it I would do it on the inner case where it is not visible and put screens in as to stop debris from getting in the belt.

as for a left side adjuster it is a must for proper tracking of the belt and long life.
 
OK, I'll bite. What's a left side adjuster and is it relevant for a Mk3 on its way to a belt drive conversion?
 
highdesert said:
YES, I feel it is very important that a belt primary have a left side threaded gearbox adjuster.
It is more critical for belt to run true than a chain, and a left side adjuster allows one to set belt run truer.
Click to expand...

So, when evaluating the bike, how do I spot this adjuster. If it's not there, is it a big deal to add?

Thanks
 
If you go to http://groups.yahoo.com/group/INOALIST/ and on the left side click on FILES, assuming you are a member
of the INOA online group, you can see I posted two pictures of my left side threaded adjuster.

If your bike is a 75 then the gearbox is pinned in place so no adjuster needed.
I do not have a 75 so I do not know how a belt would be set up, I assume the belt is purchased with the right size allowing
the correct slack that will go away as the baskets heat up

What year is the bike with belt?

no it is not any big deal to add it
 
OK, I'll bite. What's a left side adjuster and is it relevant for a Mk3 on its way to a belt drive conversion?
Click to expand...

Rick:

The MkIII had a hydraulic tensioner for the chain, so the MkIII cradle doesn't have the slotted holes that the previous models did, which facilitated tensioning the triplex primary. That caused issues when I did a belt primary conversion. The 112 tooth belt was loose enough to skip, and the 110 was a bit too tight. Fred Eaton built his own idler system, but is usually too behind on work to satisfy my impatience, so I bypassed having him make one for me. In the end I did source a 111 tooth 30mm belt that has worked flawlessly for 1741 miles this summer.
 
I have a Norvil belt drive on my Triton.
The spined bore on the clutch basket does not run exactly true with the clutch throwout bearing. So when you disengage the clutch it 'wobbles' slightly as it spins and the loose plates rattle a bit. I suspect the belt drive you have is doing something similar. It's not good but it still seems to work OK.
The more vented the cover is the more you would notice this.
My RGM belt drive on the Commando runs true. (I have vented the inside cover, and protected the holes with mesh.)
I would be interested to ask Highdesert and Bill if they do sustained runs at over 4000 rpm on the motorway. We have had belt drive heat issues on machine tools running over 4000, and ended up fitting a belt box fan system to these machines.
Stu.
 
bigstu said:
I would be interested to ask Highdesert and Bill if they do sustained runs at over 4000 rpm on the motorway. We have had belt drive heat issues on machine tools running over 4000, and ended up fitting a belt box fan system to these machines.
Stu.
Click to expand...

Does several 650 mile days on the motorway count :mrgreen: . most of my rides are 150 plus miles. you have to remember we live in a big country not a small island and I don't do the Harley TT rides aka tavern to tavern. I have to much fun riding on the mountain roads around my neck of the woods :D
 
bigstu said:
I have a Norvil belt drive on my Triton.
The spined bore on the clutch basket does not run exactly true with the clutch throwout bearing. So when you disengage the clutch it 'wobbles' slightly as it spins and the loose plates rattle a bit. I suspect the belt drive you have is doing something similar. It's not good but it still seems to work OK.
The more vented the cover is the more you would notice this.
My RGM belt drive on the Commando runs true. (I have vented the inside cover, and protected the holes with mesh.)
I would be interested to ask Highdesert and Bill if they do sustained runs at over 4000 rpm on the motorway. We have had belt drive heat issues on machine tools running over 4000, and ended up fitting a belt box fan system to these machines.
Stu.
Click to expand...

I wonder if the Sureflex plates Bill is running would reduce the rattle?
 
I am not a good example for sustained riding over 4000rpm with the belt primary.
My Commando riding nowadays is limited to 40 mile loops cruising right at 4000 in fourth.
But it gets got here in New Mexico and the primary gets fully hot, I am confident my summer venting is working well simply by removing
all three primary inspection covers.

I am pleased to read that others seemingly have had no issues running a belt with mileages over 20,000 before routine replacement.
I will never go back to a chain primary.
My belt allows my clutch plates to remain blessedly dry, by primary is dry so no annoying leaks, the shifting feels smoother, and the
entire primary feels lighter, quieter, and smoother.
I hope my reference to the photos of my left side adjuster posted under FILES at the INOA Yahoo forum were helpful.
 
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