Tight primary chain/ second gearbox adjuster

o0norton0o · Jul 5, 2020

So, like any neurotic Norton owner, I'm always looking for trouble, inspecting stuff rather than just riding my bike 'til something breaks. I inspected my primary chain a few days ago. Wow, was it tight. I undid the tension on the bolt in the slotted hole and ran the adjuster out to add some slack. I was thinking about how it could actually get tighter and only thought similarly to Jerry's thread, that the tolerances of all the holes and bolts that go together for the parts involved, each shift a tiny amount due to the force exerted on them over time. So, even though the adjuster bolt can't move because it's locking the gearbox in the cradle, tiny amounts of play between bolt and bolt holes add up... and the slack disappears.

Does this sound reasonable? Is there another factor that I'm missing? Do those 2nd adjuster kits make any difference in maintaining proper primary sprocket spacing?

I'm thinking of switching to the CNW primary belt drive system and am wondering about controlling the possibility of my gearbox shifting again.

Comments? Wisdom? Horror stories? Good jokes? ..

EstuaryBoy · Jul 5, 2020

Did you adjust the rear chain to compensate???

Lineslinger · Jul 5, 2020

o0norton0o said:
So, like any neurotic Norton owner, I'm always looking for trouble, inspecting stuff rather than just riding my bike 'til something breaks. I inspected my primary chain a few days ago. Wow, was it tight. I undid the tension on the bolt in the slotted hole and ran the adjuster out to add some slack. I was thinking about how it could actually get tighter and only thought similarly to Jerry's thread, that the tolerances of all the holes and bolts that go together for the parts involved, each shift a tiny amount due to the force exerted on them over time. So, even though the adjuster bolt can't move because it's locking the gearbox in the cradle, tiny amounts of play between bolt and bolt holes add up... and the slack disappears.

Does this sound reasonable? Is there another factor that I'm missing? Do those 2nd adjuster kits make any difference in maintaining proper primary sprocket spacing?

I'm thinking of switching to the CNW primary belt drive system and am wondering about controlling the possibility of my gearbox shifting again.

Comments? Wisdom? Horror stories? Good jokes? ..

I will compensate on an adjustment setting when multiple fasteners are in play to help compensate for an accurate final adjustment/setting. I often go through the process multiple times before I am satisfied with the results be it looser or tighter.
One way or another you are going to talk yourself into that belt drive.

Fast Eddie · Jul 5, 2020

Given the chance, the rear chain will always pull the primary chain tight, never vice versa.

This is why you should pull the gearbox back in the slots as tight as you can, then use the adjusters to push the gearbox forward to slacken the primary chain. That way you will have taken up all of the slack in the gearbox through bolts in the direction of rear chain pull.

If you use the adjusters to push the gearbox back, you create slack in the through bolt to gearbox fit that can then be pulled back and taken up by the chain without you realising.

Comnoz once posted about this and explained it better than I can, this is just my interpretation.

o0norton0o · Jul 5, 2020

Lineslinger said:
I will compensate on an adjustment setting when multiple fasteners are in play to help compensate for an accurate final adjustment/setting. I often go through the process multiple times before I am satisfied with the results be it looser or tighter.
One way or another you are going to talk yourself into that belt drive.

yeah, I am just biding my time and waiting to see the last check from the job I am working on roll in... I know that with belt drives, the tension is even more critical than a chain, so I'm out in front of this potential problem asking about how much the 2nd adjuster helps chains (or belts) maintain their tension.

Fast Eddie said:
Given the chance, the rear chain will always pull the primary chain tight, never vice versa.

This is why you should pull the gearbox back in the slots as tight as you can, then use the adjusters to push the gearbox forward to slacken the primary chain. That way you will have taken up all of the slack in the gearbox through bolts in the direction of rear chain pull.

If you use the adjusters to push the gearbox back, you create slack in the through bolt to gearbox fit that can then be pulled back and taken up by the chain without you realising.

Comnoz once posted about this and explained to better than I can, this is just my interpretation.

I knew that the rear chain overpowered the gearbox positioning. The advice below it makes sense, thank you.

What I'm really wondering is if the adding of the 2nd adjuster is significant in improving the maintenance of primary belt/chain tension? Of course it's not that much more work or money to install it while I'm in there anyway. I just want to know what people here think of the second adjuster. Waste of money?, Essential, effective piece of equipment?? Something else??

EstuaryBoy · Jul 5, 2020

With the belt I think the primary (!) concern is keeping the shafts parallel at all times. Whereas a chain and sprocket might cope with minor deviations, a belt will wander, usually grinding itself to dust and other fun bits in the process! (Been there, done that

)

Fast Eddie · Jul 5, 2020

The overwhelming advice is to fit two adjusters, at least when running a belt.

To be honest, when I look at the set up, I can’t really see why this is so! But I run two adjusters anyway on the basis that the collective knows what it’s talking about, and, it’s better to be safe than sorry !

o0norton0o · Jul 5, 2020

thanks,... both good thoughts.

Steves · Jul 5, 2020

I still have a chain primary, I also have the twin adjusters. A few years back the kick start started the old slap to the back of the leg carry on and I thought aye this might be the old layshaft bearing thing. Had a look and it was actually the mainshaft bearing that had disintegrated. I suspect my interpretation of correct tension from the manual was somewhat amiss. I run it a little looser than I did, I check through the inspection cover every once in a while. Seems like every 5000 miles or so a Norton throws something at you to keep you on your toes. My latest "ere you go sunshine" from the old girl was ignition woes, stuck by the side of the road having been lulled into a false sense of security and not carrying any tools.

o0norton0o · Jul 5, 2020

Bummer Steves, I just decided to give mine a look cause I hadn't heard or felt any chain slap in the primary for a while. The chain wasn't taught, but it didn't have any slack at all either... so I got lucky and headed off trouble before it found me.... I hope.

cyclegeezer · Jul 5, 2020

When I installed my CNW e-start I asked Matt about installing a second adjuster. He said he doesn't.

maylar · Jul 5, 2020

cyclegeezer said:
When I installed my CNW e-start I asked Matt about installing a second adjuster. He said he doesn't.

I did, and I deeply regret it. There's no way in hell to get to the nuts with the e-start inner chaincase. Next time I have the primary apart the dual adjuster is comming off.

Mike40M · Jul 5, 2020

Maybe not your problem, but on a Manx running a full 6 laps at the TT had a very tight primary chain that could break at last lap. Hot engine plates expands.
Dents still in the chain guard on mine 58 years later.

o0norton0o · Jul 5, 2020

maylar said:
I did, and I deeply regret it. There's no way in hell to get to the nuts with the e-start inner chaincase. Next time I have the primary apart the dual adjuster is comming off.

Thanks Dave, When I looked at the second adjuster, I thought to myself that there isn't any way to turn the bolts without taking the inner primary apart. I suppose I could cut a slot in the inner case and just take the outter cover off to adjust it being that it doesn't have to be sealed anymore... Hopefully someone will have dealt with it and have a solution...

Fast Eddie · Jul 5, 2020

Prior to fitting the cNw e start I had the adjuster facing forwards. That is impossible to get to with the e start. I now have it facing backwards, and I cut away some of the protruding ‘chain guard’ off of the rear of the inner chain case. It’s a PITA to get to, but it is doable with some ground down spanners (sorry, wrenches), and once set, Matts belt so far seems to not need any further adjustment.

concours · Jul 5, 2020

o0norton0o said:
So, like any neurotic Norton owner, I'm always looking for trouble, inspecting stuff rather than just riding my bike 'til something breaks. I inspected my primary chain a few days ago. Wow, was it tight. I undid the tension on the bolt in the slotted hole and ran the adjuster out to add some slack. I was thinking about how it could actually get tighter and only thought similarly to Jerry's thread, that the tolerances of all the holes and bolts that go together for the parts involved, each shift a tiny amount due to the force exerted on them over time. So, even though the adjuster bolt can't move because it's locking the gearbox in the cradle, tiny amounts of play between bolt and bolt holes add up... and the slack disappears.

Does this sound reasonable? Is there another factor that I'm missing? Do those 2nd adjuster kits make any difference in maintaining proper primary sprocket spacing?

I'm thinking of switching to the CNW primary belt drive system and am wondering about controlling the possibility of my gearbox shifting again.

Comments? Wisdom? Horror stories? Good jokes? ..

Easier to just follow the published procedure, which would preclude this.

Tight primary chain/ second gearbox adjuster

I cheat/save time. From the bottom when carbs are in place.

seattle##gs · Jul 5, 2020

On my Atlas I put in an aluminum piece in the adjuster slot so the belt would track straight. It takes a while to do so and 3 or 4 pieces to be made each slightly longer.

johnm · Jul 5, 2020

maylar said:
I did, and I deeply regret it. There's no way in hell to get to the nuts with the e-start inner chaincase. Next time I have the primary apart the dual adjuster is comming off.
[/QUOTE

I fitted two adjusters when I installed the CNW belt drive.

It's a little difficult but can be done.

Firstly I very carefully aligned and checked for parallel runs on the front sprocket, the clutch basket, and the front and rear sprocket on the rear chain.

I dry fitted everything up and mounted the adjusters on both sides. The primary chain side adjuster is fitted so it faces to the rear.

Having checked everything was aligned I marked the faces of the adjusters nuts so I could count flats and always adjustment evenly.

The front nut on the drive side cannot be tightened with a spanner because it is impossible to reach. To tighten it you must push the gearbox back freeing up the nut and with a long screw driver tighten it carefully keeping a record of the flat. obviously also adjust the other side by exactly the same amount.

Then using a long slim socket extension tighten the primary side rear nut again counting flats pushing the gearbox forward. In parallel also tighted the other side exactly the same number of flats.

It's a bit fiddly but once you have set it up it takes only a few minutes and should be set for life.

o0norton0o · Jul 5, 2020

With Matt from CNW saying he doesn't fit one, that kind of splits the idea that the second adjuster is a necessity ... When I'm ready to do the belt drive conversion, I'll just ask him. Thank you all for your opinions.

lazyeye6 · Jul 5, 2020

With 4,000 miles now on the cNw electric start kit with the belt drive, I have had zero problems with belt alignment/degredation using just the OEM
timing side adjuster. Perhaps other belt drives have critical alignment issues?

Tight primary chain/ second gearbox adjuster

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