Seeking advice on an "oh dear!" moment

robs ss

robs ss

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Today I went up to the local shops (4km) for a few small things.
About a kilometre before I got there I could hear something was not right on the primary side - a muted whining.
When I got there I saw the problem was a rag (quite thin) between the top rear of the sprocket and the chain. the chain guard was somehow preventing it going further forward. Must have accidentally left it somewhere bad.
I cut all of the exposed rag away and turned the wheel forward by hand and removed the rest.
The drive chain was quite loose - meaning that the primary belt (cNw) would be tight, hence the noise.
I risked the 4km ride home and pulled the primary cover - the belt was drum tight.
I loosened the upper and lower gearbox bolts and the belt returned to correct tension - as did the rear chain.
I started the bike with primary cover off and there doesn't appear the be any strange noises or anything wrong visually. Was the clutch basket that easy to wobble before? Not sure.
Took it for a 10km ride and all seems okay.
I am obviously worried about the gearbox bearing and...?

Anyone else with relevant experience have any sage advice?
Cheers
 
Last edited:
You are going to have to start the tensioning from the beginning using the Workshop manual. By following this procedure the gearbox bolts will be pushed against their holes in a way that stops the rear chain pulling the gearbox backwards overcoming any forces applied by the gearbox bolts and nuts. The rear chain will always have a greater pull on the gearbox than the primary regardless of it being a chain or a belt.
 
My guess is your gearbox bearing etc are fine.

But, with this little ‘moment’ and the mileage you’ve done (and do) I would personally replace the belt as a safety measure.

The belt has been strained in a way it’s not designed to. It could have damaged it IMO.
 
kommando said:
You are going to have to start the tensioning from the beginning using the Workshop manual. By following this procedure the gearbox bolts will be pushed against their holes in a way that stops the rear chain pulling the gearbox backwards overcoming any forces applied by the gearbox bolts and nuts. The rear chain will always have a greater pull on the gearbox than the primary regardless of it being a chain or a belt.
Click to expand...
Thanks
The adjuster is just fine - didn't have to touch it.
It is the lack of adjuster on the LHS that is the problem. If it weren't for the cNw electric start I would have put an adjuster on the left - no space.
The tension on the chain pulls the LHS of the gearbox backward with the adjuster side (RHS) staying exactly where it should.
Loosening the clamping bolts allows it to "spring" back into place.
It has happened, to a lesser degree, before but over a longer time (2000 miles?)
Cheers
 
There is space for an adjuster on the LHS. Just.

Ok, it’s not really an ‘adjuster’ cos Matt’s belt never needs adjusting once set!

I fitted it not to act as an adjuster, but to act as an extra secure fixing to prevent movement.

99% of the time there is no need, hence why Matt doesn’t fit one. With my bike being far from stock, I wanted the extra security.

Although, I confess, I haven’t ‘tested’ it by leaving a rag on the chain yet !!

I did need to relieve the lip at the rear of the primary case. As I said, I would not want to use this as a regular adjustment method, but once set it does provide a nice extra level of security and / or peace of mind…

IMG_9739.jpeg
 
Yes - I have a "snail cam" plate to put in place there - but that work needs the inner primary off to fit it - so hasn't been done yet!
Can't see the details of your's - can it be fitted "assembled"?
Cheers
 
robs ss said:
Yes - I have a "snail cam" plate to put in place there - but that work needs the inner primary off to fit it - so hasn't been done yet!
Can't see the details of your's - can it be fitted "assembled"?
Cheers
Click to expand...
No, it needs to be done prior to / during assembly.

Need to drill the cradle the cradle for a start…
 
I was thinking of making some "crescent moon" shaped inserts for the cradle slots so the gearbox would be fixed in the correct location for the belt... Anyone know of any flaws in that idea?
 
o0norton0o said:
I was thinking of making some "crescent moon" shaped inserts for the cradle slots so the gearbox would be fixed in the correct location for the belt... Anyone know of any flaws in that idea?
Click to expand...
I’ve thought about that before.

My only thoughts about flaws is accuracy of the filing and the possibility of some movement when torquing up.
 
I would consider a belt change like @Fast Eddie said.

Look for oil coming out of the gearbox at the sprocket - if things got too hot, then the sprocket seal could be damaged but I suspect that the bearing is fine. A similar thing happened to a friend with a standard primary. His rear chain and front sprocket got so hot that the seal partly melted and he got a bad burn when he touched the smoking chain. His ride in that condition was much longer and he was 2-up on the bike.

If you're talking about clutch wobble with the clutch disengaged, don't worry about it if small. If it's wobbling when engaged, keep an eye on it - you could have bent your main shaft.

BTW, when you ask Matt about a second adjuster his answer is a very clear no, and I've installed several of his kits without them, so I see no need. However, I won't install other belt drives without a second adjuster. That said, I like @Fast Eddie reason for adding a second "adjuster". It simply helps lock the gearbox in position as there is no need for adjustment once adjusted initially with a cNw belt drive. I would never take a bike apart to install a second adjuster so adding a belt drive to a finished bike means it's cNw or nothing to me!
 
Fast Eddie said:
I’ve thought about that before.

My only thoughts about flaws is accuracy of the filing and the possibility of some movement when torquing up.
Click to expand...
I am not afraid of accuracy. My entire vocational career was about accuracy. Also, I think Ludwig did this to his bike and endorses the modification... Maybe he will chime in...
 
o0norton0o said:
I am not afraid of accuracy. My entire vocational career was about accuracy. Also, I think Ludwig did this to his bike and endorses the modification... Maybe he will chime in...
Click to expand...
I think he did, but I think he left some room for fine tuning adjustment IIRC ?
 
Here's one that I made, similar to Ludwig's - to fit when I get around to pulling the inner primary off!
The small button head screw is to give something to grab onto to help in-situ adjustments.
Maybe I'll have to pull my finger out!
Seeking advice on an "oh dear!" moment
 
You are very lucky. In the early 70s I found a guy on the road to Yosemite with a sportster with the entire gearbox split apart because a rag had been sucked into the front sprocket. Worse yet, the bike belonged to his friend.
 
Fast Eddie said:
There is space for an adjuster on the LHS. Just.

Ok, it’s not really an ‘adjuster’ cos Matt’s belt never needs adjusting once set!

I fitted it not to act as an adjuster, but to act as an extra secure fixing to prevent movement.

99% of the time there is no need, hence why Matt doesn’t fit one. With my bike being far from stock, I wanted the extra security.

Although, I confess, I haven’t ‘tested’ it by leaving a rag on the chain yet !!

I did need to relieve the lip at the rear of the primary case. As I said, I would not want to use this as a regular adjustment method, but once set it does provide a nice extra level of security and / or peace of mind…

View attachment 116463
Click to expand...
Wudda about one of these?
 

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marshg246 said:
I would consider a belt change like @Fast Eddie said.

Look for oil coming out of the gearbox at the sprocket - if things got too hot, then the sprocket seal could be damaged but I suspect that the bearing is fine. A similar thing happened to a friend with a standard primary. His rear chain and front sprocket got so hot that the seal partly melted and he got a bad burn when he touched the smoking chain. His ride in that condition was much longer and he was 2-up on the bike.

If you're talking about clutch wobble with the clutch disengaged, don't worry about it if small. If it's wobbling when engaged, keep an eye on it - you could have bent your main shaft.

BTW, when you ask Matt about a second adjuster his answer is a very clear no, and I've installed several of his kits without them, so I see no need. However, I won't install other belt drives without a second adjuster. That said, I like @Fast Eddie reason for adding a second "adjuster". It simply helps lock the gearbox in position as there is no need for adjustment once adjusted initially with a cNw belt drive. I would never take a bike apart to install a second adjuster so adding a belt drive to a finished bike means it's cNw or nothing to me!
Click to expand...
And for clarity, I’m not disagreeing with Matt either. Matt is clever. He’s not stoopid enough to build 11:1 CR, 920cc motors… which is the reason I wanted the extra security.
 
Well, did 50 miles today with no issues.
Pulled the primary cover off when cool and removed all clutch plates.
After a clean it "appears" all is fine. The belt looks good - but I will replace it as soon as I have a spare.
The basket wobble is not excessive, so I'm probably worrying about nothing there.
The clutch hub turns easily/quietly so unlikely to be an issue.
Hopefully I've dodged a bullet.

I will remove the primary and inspect the belt after every ride until the new belt is on.
Thanks for the comments - much appreciated.

I will update if things change and will increase the priority of fitting that LH adjuster/locker.
Cheers
 
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