23t gearbox sprocket. Problems or not. (2013)

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I have the equivalent to a 23 tooth sprocket on my bike now. It is nice on a fast highway and great for fuel mileage but I plan on going back down a bit. It takes too much clutch slipping to get underway and 4th is darn near useless on the mountain roads.

This last summer on my way back from Barbers I was cruising down a four lane at 80+ and looked at the tach. It seemed a little higher than normal. I cured it when I shifted to fourth. I had probably run 40 miles in third without even noticing. Jim
 
Here are some of my observations on the topic from past years:



I've been running a 24-tooth sprocket with a Combat 750 for about twenty years now. I'll probably never go back to something smaller. Zero-to-60 times remain comparable because you don't change out of first gear. Gas mileage improves, highway revs go way down--and if you need it there's always third gear. Having an optional overdrive is useful almost every day--with my tall 18-inch tire 4000 rpm is a leisurely 89 mph on the tollway. My rebuilds seem to last a lot longer as well.

Not only does the primary ratio establish the peak torque delivered to the gearbox, the taller sprocket also reduces rpm and torque at any given road speed compared to smaller sprockets. My '72 Combat with a 24-tooth sprocket and tall back tire is pulling 4000 rpm at an indicated 89 mph--2000 rpm below peak torque for that engine.

Bikes with standard gearing and camshafts are pulling around 5000 rpm at that speed, which corresponds to peak torque. It is the surplus torque and horsepower that allows these bikes to pull right on up to redline in top gear. It also contributes to the sense that the engine is "busier" than need be at tollway speeds.

My gearbox has been nearly bulletproof since I put in a roller layshaft bearing twelve years ago. The three sleeve-gear bushings are the components most susceptible to wear. Eliminating the mainshaft circlip and moving the entire primary closer to the center line seems to have extended the bushing life to around 30,000 miles.




Tim Kraakevik
kraakevik@voyager.net
 
Hi Reggie
for my two penny's worth I would add that 22T would be the tops I would go to, or your friend will find he has to slip the clutch way too much starting off (even solo) and around towns and cities will find it cumbersome to say the least. Also with the UK speed limits and them there hills of Yorkshire, he will be changing down far too often.
Cheers
JohnT
 
Dances with Shrapnel said:
If I have ever heard arguements for a five speed, this thread is it.

What (if anything) was Norton thinking of?
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No doubt about that.
I have a wide ratio 5 speed setting on my shelf. Now if I can figure out how to start the bike with no kickstarter. Jim
 
21 tooth with the Norvil belt drive is similar to 22 with triplex. Or so I've heard.
 
Snorton74 said:
21 tooth with the Norvil belt drive is similar to 22 with triplex. Or so I've heard.
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Pretty much. 2:1 as opposed to 2.19:1 if memory serves me. Hence my earlier post where I had a 23 tooth sprocket on and was whizzing by everybody at what I thought was a normal highway speed. Also explains why it wouldn't pull top speed in fourth.
 
I have posted this before. I run a 29 tooth triplex primary matched to a 19 gearbox sprocket. It gives me all I could wish for, no noticeable, detrimental, change in acceleration, fast cruising is 80mph @ 4000rpm...
 
Good to hear some common sense about high 4th gears being not much use in the mountains! Nearly every meet I talk to someone whose had a Commando or had ridden one and it used to climb 1 in 6 (17%) hills in top with ease 2 up!! So torquey they never needed to change gear :wink: Ok now someone here will tell me it's true. My 35/72 Norvil belt and 21/42 gives 18.1/1000 in top and that's OK. Of course it would be nice to cruise at less rpm but it's a compromise.
BTW Marine, whats Poole bike night like these days, worth a visit or is it all crotch rockets and hardly ablesons? My Dad lives there and was thinking I should ride down one night.
 
Hi,

my 850 had a 23th sprocket and I changed over to 22th. With 23th you often have to shift down to the first gear, when you ride sharp corners or when you turn at a city crossing.
With the 22th sprocket everything is fine.

Ralf
 
triumph2 said:
Pretty much. 2:1 as opposed to 2.19:1 if memory serves me.
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Norvil offers a wide choice of ratios in their belt drive kits. I didn't specify a ratio when I ordered mine so they supplied the standard conversion which is 34/72 or 2.118:1. I run a 21 tooth gearbox sprocket.
Yes the original chain ratio is 2.19:1.
The Norvil chart lists 14 optional ratios from 1.714:1 to 2.25:1

Martin
 
Keith1069... Pooles ok on Tuesday. Only 2 Nortons last week , me and a yellow S. come on down when it gets warmer, you'll always get the 'oh that isn't standard' types who only polish their bikes, but what the hell. There is a good assortment of iron...
 
Dances with Shrapnel said:
For what it is worth, I had some very bad experiences with a Jason brand belt but this is with a ultra short stroke Norton with +85RWHP. They would break and strip teeth on a very regular basis. Holmeslice put me on to a special supplier out of North Carolina and those problems are now in the past.

The point is that not all belts are the same.

I would not think the lay shaft bearing durability is a factor one way or another when choosing a sprocket. You do want a good bearing there.
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Hi DWS, what kind of belts are those : HTD 8mm? as I could be interested by this supplier.........if you want to give that info!!
 
Keith1069... Pooles ok on Tuesday. Only 2 Nortons last week , me and a yellow S. come on down when it gets warmer, you'll always get the 'oh that isn't standard' types who only polish their bikes, but what the hell.
Click to expand...
Cheers, I will take a look. (apologies for taking the thread off course).
 
All this sprocket talk.. I have been wanting to hop up to a 21 tooth from my 19. I can't imagine having a 24 tooth though, seems really tall. Doesn't anyone have a 19 around here?
 
Has anyone with an 850 had issues pulling 4th gear with a 23T CS sprocket? My friend is complaining his 850 is a slug with the 23T in 4th.
 
George Hirvela said:
Has anyone with an 850 had issues pulling 4th gear with a 23T CS sprocket? My friend is complaining his 850 is a slug with the 23T in 4th.
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Mines a 23T 850 (with only a single 34 Amal carb). This is probably a personal thing and depends on riding style and preferences. My experience is that I'm completely delighted with it. It feels like it pulls like a train from 2500rpm (50mph) and purrs at 70mph, where I'm happy there's plenty still available for overtaking without changing down. I also regularly ride a modern 1,000 Kawasaki, so I probably should notice if it was a problem.

General spirited riding, without ever taking it beyond 5-5,500rpm, It keeps up happily with a modern T120 Bonneville (both leave an Enfield 650 Interceptor behind in the distance) and I still tend to slot it into 4th to ride the faster roads, not dropping down for bends. It's not very hilly round here though.

Connecting with the older, earlier posts:
- I checked recently and I have a replacement roller layshaft bearing
- I'm not slipping the clutch that much, uphill 1st gear pull away is still fine
- Not getting 60 to the UK gallon (50-55mpg)
- No plan to change to a smaller sprocket (still tempted by 2 x carbs though).
 
George Hirvela said:
Has anyone with an 850 had issues pulling 4th gear with a 23T CS sprocket? My friend is complaining his 850 is a slug with the 23T in 4th.
Click to expand...
As bought, my 850 had a single Mikuni and a 23 tooth sprocket.

I basically agree with Mark in that it was a nice torquey ride. It ran out of puff somewhere over 5K but that wasn’t the sprockets fault.

It will give lower rpm at a given cruise speed, which is nice. But it will take the edge off of traffic light drag starts.

Mark, my only difference of option in your statement is the other riders and bikes. A 1200cc T120 will easily leave you behind if you’re only revving to 5,500 if he wanted to. And the Enfield pilot could easily keep up if he wanted to!
Perhaps they’re just being kind?
 
Fast Eddie said:
....

Mark, my only difference of option in your statement is the other riders and bikes. A 1200cc T120 will easily leave you behind if you’re only revving to 5,500 if he wanted to. And the Enfield pilot could easily keep up if he wanted to!
Perhaps they’re just being kind?
Click to expand...
I don't think the Triumph handles well enough, but on more open roads that would be the case. The Enfield on the other hand, just seems short on acceleration. 47bhp at the crank, but quite a big bike. He's ridden since his first FS1-E, he knows what he's doing. It doesn't pull enough out of the bends and drops back. Only happens when we have the odd moments of getting to some good roads and wanting to play. But he admits it falls short then. He loves the bike though, it looks good too.
 
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