Stock Countershaft (gearbox) Sprocket '74 Norton 850 Commando?

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Dan1950

Dan1950

1974 MK II Roadster
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Someone mentioned changing to a 22 tooth countershaft sprocket on the 850 Commando for better highway cruise.. Was just curious as to how many teeth they come with from the factory?
 
The advertising brochure we got in the US for 1974 models says they were fitted with the 20T sprocket at the factory, and that alternate (21T and 22T) sprockets were available to be fitted at the dealers. The brochure for the 1975 models also lists the 20T as standard. Not sure if other sprockets were standard for other geographical areas.

Ken
 
Us Brits got 22T on the Mk3... I think general consensus was you lot were impressed by 0-60 times whereas we got all excited over top speed....
 
lcrken said:
The advertising brochure we got in the US for 1974 models says they were fitted with the 20T sprocket at the factory, and that alternate (21T and 22T) sprockets were available to be fitted at the dealers. The brochure for the 1975 models also lists the 20T as standard. Not sure if other sprockets were standard for other geographical areas.

Ken
Click to expand...
You are right with USA and Canadian market. They were 21T standard in Europe. Moving larger sprocket cause excessive stress to the transmission.
 
My 850 with series no. 307175, was delivered to Norway with T24. This was far too high gearing. For my use on winding roads, the T21 fits perfectly.
 
750 Interstates and 850's in US had 20 tooth sprockets. 850's had lower compression and a heavier flywheel than 750's, so less responsive to acceleration in mid range. As I have both, a 750 with 10:1 CR with a 19T sprocket on a Quaife 5 speed is my preference. Larger sprockets may make highway riding easier on the engine, but that's the most boring riding for me.
Belt drives may also change the final drive ratio slightly.
 
Dan1950 said:
Someone mentioned changing to a 22 tooth countershaft sprocket on the 850 Commando for better highway cruise.. Was just curious as to how many teeth they come with from the factory?
Click to expand...
My 74 MKII came with a 20 (US market) and I've never had reason to change it. It's about 16 mph per 1000 RPM by my clocks. I do a lot of 35-50 mph cruising and at 40 mph it sits at 2500 rpm with excellent throttle response and minimal vibration. It'll cruise at 70 mph / 4400 rpm all day, no sweat. A bigger sprocket will lower the rpm at around-town speeds and put you below the isolastics minimum working range. You'll get buzzing in the feet and hands. If you intend to have a highway cruiser and not an all-round street bike however, then it's your choice.
 
IMHO - 20T represents probably the best compromise for mixed riding, for all the reasons that Dave mentioned above. I am running a 20T on my Combat - works great.
 
IMHO, you dont get a vintage Commando for freeway cruising. Now, for highway cruising in the Adirondacks a 21T would be ideal.

I had a 20T on for most of my 74's live in Seattle, and it was great for that city life and absolutely fine on mountain cruises. I put a 21T on with a rebuild here in NZ, and for the twisty hilly roads here with a 60mph speed limit it is fantastic.
 
It really depends on where you live, how fast you mostly ride and how much you weigh.
I am geared for 3750 at 70. In the hilly area I live it is just a tad high. However I run a TTI
five speed so I can just drop down into fourth.
 
Onder said:
It really depends on where you live, how fast you mostly ride and how much you weigh.
I am geared for 3750 at 70. In the hilly area I live it is just a tad high. However I run a TTI
five speed so I can just drop down into fourth.
Click to expand...
How many teeth ?
 
In my mouth or on the sprocket?
Well I run the TTI and the BNR belt so my numbers will not make much sense for the standard Norton.
Running 22 on the box. Out here in the hilly SW really should go to 21. However I did lower the first
gear set which solved the low end issues. I need to move to Norfolk.
 
Onder said:
In my mouth or on the sprocket?
Well I run the TTI and the BNR belt so my numbers will not make much sense for the standard Norton.
Running 22 on the box. Out here in the hilly SW really should go to 21. However I did lower the first
gear set which solved the low end issues. I need to move to Norfolk.
Click to expand...

I‘m running a TTI with cNw belt and a 21 tooth and it’s definitely too low for me. The cNw belt is very close to stock ratio BTW. However, the inconvenience of the lower than ideal gearing has not yet managed to outweigh the inconvenience of changing the sprocket !!
 
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Not being a scratcher or track day man I find 20t suits my needs here in the UK adequately. Useful in traffic where it keeps the revs in the sweet spot, and bimbling round the country lanes...
But, still enough at the top end to get home via the motorway if necessary :-)
 
I have no experience of other Commandos. Back roads are in 3rd gear and in the sweet spot, town us 2nd gear and flexible and pulls well. Dual carriageways / freeways, 70mph is 3,500 and relaxed, but still plenty of go for overtakes. 22T, 850.
 
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