1972 750 Hi-Rider

quawk said:
As an aside to that, it was also mentioned that owners would change drive sprockets to change gearing, rather than the rear sprocket because the rear sprocket was cast into the rear hub and only one tooth count sprocket was available. Have I read that correctly, because that seems so odd? If that's the case what happens when/if the rear sprocket needs replaced? Chains and sprockets are commonly replaced wear items on most bikes.
Click to expand...

You change the gearbox sprocket (19-25t).
andover-norton.co.uk

Norton Parts Drawings - Genuine Norton Factory Parts - Commando Parts -

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk
 
grandpaul said:
Replace the hub, service the bearings, and off you go.
Click to expand...
Still, replace the entire hub because the sprocket is worn? I realize we didn't engineer theses bikes, but that seems like a design mistake. Is this the only modern (relative term) bike built like this because it has to be the first (and only) bike I'm aware of that didn't have a replaceable rear sprocket.
 
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quawk said:
Still, replace the entire hub because the sprocket is worn? I realize we didn't engineer theses bikes, but that seems like a design mistake. Is this the only modern (relative term) bike built like this because it has to be the first (and only) bike I'm aware of that didn't have a replaceable rear sprocket.
Click to expand...
You don't have to use the stock hub and/or wheel. Many find the cush scenario to be lacking as well. Honda hubs, Suzuki hubs, etc, are easy to come by, but require some amount of fettling to fit.

A lot of decisions made by Norton at the time were based on, "That's how we've always done it, so that's how it will be." We don't have to fall into the same mindset, 50 years on.

The answers to these questions tend to get expensive...
 
quawk said:
As an aside to that, it was also mentioned that owners would change drive sprockets to change gearing, rather than the rear sprocket because the rear sprocket was cast into the rear hub and only one tooth count sprocket was available. Have I read that correctly, because that seems so odd? If that's the case what happens when/if the rear sprocket needs replaced? Chains and sprockets are commonly replaced wear items on most bikes.
Click to expand...

You have good instincts. The stock norton set up is odd, and creates a few quirks. As you said, a worn rear sprocket involves an entire new brake drum on the rear since they are integrated. Also, if you want to change your sprocket ratio, you have to disassemble the primary completely to change the front sprocket... The other issue with stock commando rear tire/hub/rim is that the rim is heavy and narrow. A wider lighter rim gives better tire choice, lower unsprung weight, a better cush drive performance to hopefully reduce impact on the gearbox, and an easily changed rear sprocket... It also gets rid of the 2 part rear axle which has been known to occasionally break at the end of the threads inside the hub and I run a tubeless tire...

I thought the stock set up was insane so swapped out to yamaha cast wheels to get over all the stock limitations. I can even buy a "sawcut" rear sprocket that is 2 pieces that can be changed without taking the wheel or chain off...

adapting cast wheels to commando




that was an early picture before I converted my commando to interstate trim, bags, fairing, rearsets. It looks better as a finished conversion. Drum brake on the timing side with a fat looping cable from the brake lever on the primary side over the rear fender then down the swing arm... No need to fool with the old technology.

20230806_163456.jpg
 
o0norton0o said:
You have good instincts. The stock norton set up is odd, and creates a few quirks. As you said, a worn rear sprocket involves an entire new brake drum on the rear since they are integrated. Also, if you want to change your sprocket ratio, you have to disassemble the primary completely to change the front sprocket... The other issue with stock commando rear tire/hub/rim is that the rim is heavy and narrow. A wider lighter rim gives better tire choice, lower unsprung weight, a better cush drive performance to hopefully reduce impact on the gearbox, and an easily changed rear sprocket... It also gets rid of the 2 part rear axle which has been known to occasionally break at the end of the threads inside the hub and I run a tubeless tire...

I thought the stock set up was insane so swapped out to yamaha cast wheels to get over all the stock limitations. I can even buy a "sawcut" rear sprocket that is 2 pieces that can be changed without taking the wheel or chain off...

adapting cast wheels to commando




that was an early picture before I converted my commando to interstate trim, bags, fairing, rearsets. It looks better as a finished conversion. Drum brake on the timing side with a fat looping cable from the brake lever on the primary side over the rear fender then down the swing arm... No need to fool with the old technology.

View attachment 111897
Click to expand...


I don't know if it was good instincts, probably more like experience and logic. As I said, nearly all, or at least most other bike makers used a replaceable rear sprocket because to me, and I'd guess to most other engineers (which I'm not) it made sense to make them replaceable. Out of all the possible replacement, other brand wheel/tire/hub/sprockets did you land on the Yamaha set up that you used? Was it your idea, or had someone else came up with this combination?
 
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Though not the norm, the rear integral drum/sprocket does go a long way....I'm at 25k miles on my original and only now starting to think of renewing it...and only b/c the rear brake seems likely worn a bit out of round. The sprocket teeth are fairly wide for the loads taken. Cost of new drum/sprocket is around $200 CDN here...No biggie if replacing every 25k (or 50 years, which ever comes first!! ;-) )

I think you need to stop over thinking the niggles of the Commando design/ownership....and just focus on if this bike scratches an itch for you. They are very popular in the classic world for a reason or two.....
 
quawk said:
Upon doing much research, as I posted earlier, about the layshaft bearing issue, it was mentioned by some that the use of a 22 tooth gearbox drive sprocket was suspected as a culprit contributing to the failure of the bearing, seemingly from increased loading. As an aside to that, it was also mentioned that owners would change drive sprockets to change gearing, rather than the rear sprocket because the rear sprocket was cast into the rear hub and only one tooth count sprocket was available. Have I read that correctly, because that seems so odd? If that's the case what happens when/if the rear sprocket needs replaced? Chains and sprockets are commonly replaced wear items on most bikes.
Click to expand...

The quality of British steel combined with the (lack of) power of British engines, means those drum sprockets last a looong time !
 
quawk said:
I don't know if it was good instincts, probably more like experience and logic. As I said, nearly all, or at least most other bike makers used a replaceable rear sprocket because to me, and I'd guess to most other engineers (which I'm not) it made sense to make them replaceable. Out of all the possible replacement, other brand wheel/tire/hub/sprockets did you land on the Yamaha set up that you used? Was it your idea, or had someone else came up with this combination?
Click to expand...
I actually did a ton of research looking at rim composition, diameter, and widths of bike model wheels over the course of a few months and eventually I found these on a bike being parted out on craigslist which were a "close enough fit" to my wish list for me. I actually drove 3 hours each way to get them. The vintage Cambray cast wheels for norton commandos are rare as hen's teeth. Usually a person selling them wants $500 or more for them. I got both my wheels for $120. There is also Lester wheels and Morris from back in that era, but you don't see them around anymore.

I did do a lot of modifying. I used the yamaha rear axle, so I had to mill the slots for the larger axle in the swingarm. The reason I did this modification was to get all the improvements, not just some of them. I just thought I could save some money adapting cast wheels when I was at a point where I needed new tires, so rather than buy new tires for stock rims I made the switch and bought new tires for the cast alu wheels. As with most projects, I spent money like crazy and in the end there was little if any money saved, but I liked the result.

One of the cooler things was being able to change the rear sprocket size. Since there is 2 times the number of teeth on the rear sprocket, you can get adjust the ratio for half steps by comparison to front sprocket adjustments. The sprocket company also makes split saw cut sprockets that the halves can be unbolted from the hub while on the bike, one half at a time and replaced with a different size sprocket by just slackening the rear chain adjusters.... (not that people go around changing their ratio once their bike is set up)
 
quawk said:
I don't know if it was good instincts, probably more like experience and logic. As I said, nearly all, or at least most other bike makers used a replaceable rear sprocket because to me, and I'd guess to most other engineers (which I'm not) it made sense to make them replaceable. Out of all the possible replacement, other brand wheel/tire/hub/sprockets did you land on the Yamaha set up that you used? Was it your idea, or had someone else came up with this combination?
Click to expand...
Once you replace the sprocket, it will likely last for the rest of your life. Even if you don't replace the sprocket, you likely won't wear out the existing one if it looks good now.
My 1975 MK3 has done 48000 miles from new and is still on its original rear sprocket. It's in good shape at that.
Cast iron can be weak stuff but it wears amazingly well. I guess that is why it is also used for cylinders and liners.

My modern bikes have easily replaceable sprockets made of various metals, none are cast and all need replacing fairly often. The Thruxton r sprocket was kaput at 23,000 kms, about 16,000 miles.
So the Norton rear sprocket setup isn't as crazy as it looks.
No sprocket bolts to fall out or come loose either. I have seen that happen on two bikes that have bolted on sprockets.
It's really not that difficult to change the ratios via the gearbox sprocket. The bikes (particularly the 850) have great torque and don't require being kept " in the power band" The powerband of the stock bike is pretty much the whole rev range. Overall ratio isn't that critical. Find the gearbox sprocket size you like and away you go. I was able to fit a 530 xring chain on my MK3, so that is almost a set it and forget it drive arrangement for me.



Glen
 
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Onder said:
On the green Norton: where did that rear guard come from? Admit I had to check the previous pix t make
sure they didn't appear on other Hi Riders.
Click to expand...
Hi O, the rear fender on the Green bike is a fender blank I had laying around. I was going to change the front wheel on my Harley from a 21" to a 16" and never did. The blank is for a Harley Wide Glide front end with a 16" wheel. I thought it might look good on the Norton adding a little more color to the sheet metal. Where I mounted the turn signals would normally be the mounting points on the fork sliders of the front end.

The bike is a 74 Roadster, not a Hi Rider. I like the high handlebars because I have bad cervical problems and need to sit more upright. The rear Norton wheel is a factory 19" with a 21" front wheel. Sometimes I change it back to a 19" front. Happy New Year!
 
o0norton0o said:
I actually did a ton of research looking at rim composition, diameter, and widths of bike model wheels over the course of a few months and eventually I found these on a bike being parted out on craigslist which were a "close enough fit" to my wish list for me. I actually drove 3 hours each way to get them. The vintage Cambray cast wheels for norton commandos are rare as hen's teeth. Usually a person selling them wants $500 or more for them. I got both my wheels for $120. There is also Lester wheels and Morris from back in that era, but you don't see them around anymore.

I did do a lot of modifying. I used the yamaha rear axle, so I had to mill the slots for the larger axle in the swingarm. The reason I did this modification was to get all the improvements, not just some of them. I just thought I could save some money adapting cast wheels when I was at a point where I needed new tires, so rather than buy new tires for stock rims I made the switch and bought new tires for the cast alu wheels. As with most projects, I spent money like crazy and in the end there was little if any money saved, but I liked the result.

One of the cooler things was being able to change the rear sprocket size. Since there is 2 times the number of teeth on the rear sprocket, you can get adjust the ratio for half steps by comparison to front sprocket adjustments. The sprocket company also makes split saw cut sprockets that the halves can be unbolted from the hub while on the bike, one half at a time and replaced with a different size sprocket by just slackening the rear chain adjusters.... (not that people go around changing their ratio once their bike is set up.
Click to expand...
I really like the look of your bike in the posted pics and can appreciate the time, work, and ingenuity it took to make this swap happen. Great job. That said I'm really a sucker for the spoked wheels, front drum brake, and the pea shooter mufflers. To me, those things say Norton. I'm sure your bike outperforms the original setup with your mods, especially the front disc brake. I realize Norton did start using a front disc brake
 
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worntorn said:
Once you replace the sprocket, it will likely last for the rest of your life. Even if you don't replace the sprocket, you likely won't wear out the existing one if it looks good now.
My 1975 MK3 has done 48000 miles from new and is still on its original rear sprocket. It's in good shape at that.
Cast iron can be weak stuff but it wears amazingly well. I guess that is why it is also used for cylinders and liners.

My modern bikes have easily replaceable sprockets made of various metals, none are cast and all need replacing fairly often. The Thruxton r sprocket was kaput at 23,000 kms, about 16,000 miles.
So the Norton rear sprocket setup isn't as crazy as it looks.
No sprocket bolts to fall out or come loose either. I have seen that happen on two bikes that have bolted on sprockets.
It's really not that difficult to change the ratios via the gearbox sprocket. The bikes (particularly the 850) have great torque and don't require being kept " in the power band" The powerband of the stock bike is pretty much the whole rev range. Overall ratio isn't that critical. Find the gearbox sprocket size you like and away you go. I was able to fit a 530 xring chain on my MK3, so that is almost a set it and forget it drive arrangement for me.



Glen
Click to expand...
The front sprocket always wears out loooong before the rear .
 
worntorn said:
Once you replace the sprocket, it will likely last for the rest of your life. Even if you don't replace the sprocket, you likely won't wear out the existing one if it looks good now.
My 1975 MK3 has done 48000 miles from new and is still on its original rear sprocket. It's in good shape at that.
Cast iron can be weak stuff but it wears amazingly well. I guess that is why it is also used for cylinders and liners.
Click to expand...
It is my understanding that the rear sprocket is case hardened. If true, until the hardened layer is worn away there should be very little wear. On other bikes, they are often mild steel or an aluminum alloy which machines easily but is not hard. I believe that cast iron with a steel chain rubbing against it would wear out very fast if not case hardened and that the front sprockets are not hardened in any way.

Not an expert, but I asked about having 530 rear sprockets turned down for 520 chains and was told no due to the case hardening and them being unable to re-case harden.
 
marshg246 said:
It is my understanding that the rear sprocket is case hardened. If true, until the hardened layer is worn away there should be very little wear. On other bikes, they are often mild steel or an aluminum alloy which machines easily but is not hard. I believe that cast iron with a steel chain rubbing against it would wear out very fast if not case hardened and that the front sprockets are not hardened in any way.

Not an expert, but I asked about having 530 rear sprockets turned down for 520 chains and was told no due to the case hardening and them being unable to re-case harden.
Click to expand...
There is way more pressure(s) exerted on the front sprocket than the rear . It's about size and how the forces are distributed . The front takes more pressures resulting in wear first .
 
Torontonian said:
There is way more pressure(s) exerted on the front sprocket than the rear . It's about size and how the forces are distributed . The front takes more pressures resulting in wear first .
Click to expand...
This is true. I recall changing my Motocrosser front sprocket from a 19 down to a 17. The 17 seemed to wear at about twice the rate of the 19. It was as though tooth pressure went past a critical point .
The front sprocket gets the double whammy of higher tooth pressure and roughly 2x as many revolutions per mile vs the rear.
The original front sprockets were very hard, the file just slides across without cutting in. Some of the replacements are soft, easy to mark with a file.

Glen
 
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