Primary belt drive problem

Anyone experienced problems, e.g. premature bearing wear, of the Norvil 30mm belt drive conversion?
My clutch basket has developed some play, allowing it to move ~0.5mm TIR in and out from parallel, measured near the circumference of the latter.

May be I am splitting hair?

The reason I am asking is my belt will not stay put when I crank the engine manually, it moves outwards.
My gearbox shaft is parallel to crank and I was thinking that the above alone could explain this tendency of the belt.

Any suggestions welcome.
Thanks
Aris

Maybe the mainshaft circlip got crushed/overtightened.

No, I did the measurement with the basket out. That is on the bench.
But thanks!
Aris

Hehe more proof hair splitting perfect pulley or sprocket alignment in plane of drive tension don't matter a whitworth if the gear box or crank shafts wobble so suspect too much time in lower gears w/o Dexron type ATF inside so main shaft sleeve bushes worn too much slack. Do check the basket circlip but not likely the issue or would of had belt run off on 1st leaving to ride. The only time sleeve bushes get any lube to enter is time spent in top gear as buses below resting oil level and lower gears spin slings oil out not suck any in.

Belt too GD tight! Seems people adjust these with the mind set of a chain. They just can't get their mind around the fact that these belts will not loosen up over time.
The reality is that they will tighten either from the gearbox pulling back if the secondary adjuster is not employed or from expansion of the hub when heated up under normal running conditions, even if ever so slightly.

Adjust it as loose as you dare (well beyond the recommendation) and it will run fine forever.

I loosened mine just to the point where the belt would jump a tooth on the crank hub when kicking over, then bring it just so it don't. It's been perfect for 3 years now. Just to add, I run my bike pretty darn hard.

Belt too GD tight

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I am with Pete on this observation

I have had the same 30mm Norvil belt as you have for some 15 years now, it does not wear and it tracks straight

1) set the belt tension when the primary is cold so that you can twist the upper belt about 70 degrees, NOT 90

2) do you have a left side threaded gear box adjuster installed?

I would not run a belt without one

Forget the crankshaft to gearbox main shaft parallel stuff

insure the belt is set on the back section of the rear clutch sprocket, it wants to be there

paint the outside edge of the belt white and rotate the motor watching to see if the paint gets worn off, should not

set the gearbox so the belt itself tracks true on the front sprocket using the two gearbox adjusters and forget
they parallel theory

Kool_Biker said:

The reason I am asking is my belt will not stay put when I crank the engine manually, it moves outwards.
My gearbox shaft is parallel to crank and I was thinking that the above alone could explain this tendency of the belt.

Any suggestions welcome.
Thanks
Aris

Click to expand...

When I set mine up, I used 2 right angle squares. With one coming off the clutch hub and the other coming off the crank hub, I checked that the perpendiculars had about a 1/8th inch gap to the outside with about an 8 inches from the alignment plane. This left the setting of the alignment ever so slightly open. This keeps the belt running toward the inside but not rubbing on either the inner primary nor the inner disk of the crank hub.
Along with this, it is, of course, not necessary to align the teeth as you would with a chain so I try to keep the clutch hub as close as possible to inboard side. This minimizes unwanted leverage against the related components of the clutch and main shaft and maximize stability of the clutch hub. Leaving nothing to chance, I re bushed the sleeve gear, got a fresh main shaft, and installed an outrigger bearing.

Pete is right, when the belt is not too tight it is not nearly as critical as far as pulley alignment. Jim

Some really great suggestions!
Will get on with it asap as, yes, I have probably been running my belt way too tight (as per original instructions though ..).
Cheers and thanks a lot.
Aris

I've pestered world class experts world wide on belt tension and all say should be able to twist belt to essentially 90' no matter its free run lenght or width of belt which in our cases allows belt [cold] to be worked on/off mostly by hand with some blunt probes to assist, leaving gearbox adjusters fixed. Alway check when hot to be sure. Its a good thing not to have to check primary if oil seen. Chains have more give it seems than belts and only takes one over tight event to warp AMC shafts so be pensive till clutch basket verified stable plane of rotation.

I have probably been running my belt way too tight (as per original instructions though ..).

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Norvil instructions quote 33mm total play, so not tight

I also run a Norvil 30mm and lost teeth on first belt at 25k miles in 2012. I have double adjusters and run with 30mm vertical play. See pic. I do get some dust debris so I know its not in perfect alignment but with it apart now I plan to try and measure it more successfully. What I have noticed is that the anodizing is wearing (worn) through on both pulleys, now at 32k miles. That cannot be good for belt teeth as the surface is looking pitted.

1up3down said:

Belt too GD tight

Click to expand...

2) do you have a left side threaded gear box adjuster installed?

I would not run a belt without one

Click to expand...

I do not, and I see now it makes sense to add this. Good point!

Aris

About only way teeth can come off on the low power of Commando's is if the belt missaligned in flight to rub on front pulley plates &or grit worn, then soorn after a few teeth leave the whole belt can unravel. Peel's belt took anodize off teeth and valleys too but don't know if that matters any but for teeth wear. A loose flung clutch or crank nut cut 3 holes in Peels last belt and nothched teeth, one could stick a pencil through biggest hole yet ran it a few 1000 miles playing sports bikes and dirt bike games w/o issue. That socket 30 mm stretch still looks a bit tight to me but if can still slide belt on/off cold then should be about right hot. Get us a photo to the belt deflection at road going temps please.

I picked my belt kit up on a trip back home and was told by Les Emery that the trick was to get the belt to run true without the side plates on the front pulley then tighten everything up and install the side plates. I did this and have been running problem free since about 1992. I'm using two adjusters to accomplish the alignment. My only mistake was to install the second adjuster the same as the the original which made it a SOB to adjust but not a huge hassle as I haven't needed to adjust it once it was set.

I want to add one final comment regarding primary belt tension

most instructions say to set the belt tension at about 35mm to rung resting to push up limit with the primary cold

this translates to around a full 90 degrees twist in the belt itself

the instructions say to do this as, in my opinion, an overkill against someone erring on the side of too tight

everyone knows that in a fully heated up primary the front and rear sprockets heat up, expand, and take up the slack

if you check the belt tension with the primary hot and slack removed, you can still detect a fair amount of slack in the belt tension, this tension tells you that the belt is set too slack when cold

at the risk of being flamed for blasphemy I set my belt cold at about 26 mm or 70 degrees of twist

consider that the belt is tensioned across the top while the bottom rung still has slack

and it is this what I consider excess or too precautionary slack that causes the belt to both slap the bottom of the primary and also to wear more rapidly away the hardening surface or both belt sprockets in addition to the belt teeth, especially when the primary is not under load such as when idling in neutral

consider not being afraid of taking a little slack out of the recommended installation amount

Yeah man nothing beats setting hot then see how it hangs when cold. My belts set 90ish cold tightened up to resist twisting to 70'ish on full heating. Same thing can be done on drive chain setting it just so with sprockets at farthest distance in suspension travel. Its a bit concerning to me to have to turn cranks so much to make sure belt self centers as wears on cam but only way I know to be sure. I mostly get mine dialed in w/o key in front pulley so it spins on taper but tested running exposed before sealing up. My belts seem to flap most right before top of crank pulley so tension up so mostly misses the dowel bosses. The more I tightened belt up the faster the fapping got like guitar string but it still seemed to flap about as far out of line. I know what worked for me so far but that don't mean its optimalized tension - I'm still creeping up on. Btw there are charts that show the ideal pulley centers distance going by teeth count of belts and each pulley but don't know if our pulley centers are stable enough to go by that but would be interesting to compare. Here's good factoids article for GoldieLocks trial error guidance.


Here's good factoids article for Goldie Locks philosophy on trail error guidance.
http://www.sdp-si.com/web/images/Belt_f ... _Guide.pdf

synchronous belt tension calculation I've not looked into so far, maybe others can pull out what applies.
https://www.google.com/#q=synchronous+b ... alculation

Charts if ya can believe manufacturers with legal departments
http://www.pfeiferindustries.com/docume ... 0Chart.pdf

Here's the new digi age way to measure belt tension in our range, once ya calculate the best tension. Price ranges from couple hundred to over 1000. Might be able to tune spokes with it too. Piink Plonk Plunk.

https://www.youtube.com/watch?v=KKQBhis1sjk

triumph2 said:

I'm using two adjusters to accomplish the alignment. My only mistake was to install the second adjuster the same as the the original which made it a SOB to adjust but not a huge hassle as I haven't needed to adjust it once it was set.

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I am about to purchase & install a 2nd (drive side) adjuster. So exactly what do you mean by 'my only mistake' above, and how can I avoid?
Plus, is there a trick to adjusting with the two adjusters I might be missing? Beyond obvious?

Thanks in advance, Aris

Kool_Biker said:

So exactly what do you mean by 'my only mistake' above, and how can I avoid?

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installing-left-side-adjuster-t4933.html
double-sided-gearbox-adjuster-big-pics-t5470.html#p51286

Lots of useful info.
Thanks!