22T sprocket

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B+Bogus

B+Bogus

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Now I've got my MkIIa all settled down I'm going through the remaining 'issues' - such as they are, and the number one on the list was the massively overgeared nature of the bike.
I just replaced the standard 22T sprocket for a 20T and took it for a spin - what a difference! The gear ratios actually make sense now :p

Previously I was going for rides without using 4th at all, so it definitely needed sorting.
I'm still going above 70 (Ahem, er...55, Officer) before shifting into 4th, so it isn't undergeared, and it's far more driveable in built-up areas now - before I was either rattling my fillings at tickover in second, or revving a little too high in first to keep the ride smooth. It was also a bit of a pig in slow traffic (not helped by the hair trigger clutch), but I haven't tried that one yet ;)
The biggest difference I've noticed is that I now seem to be in the right gear after downshifting for corners without having to think twice about it - this was nigh on impossible before; I can now use the engine braking how I like it, rather than none or too much.

I don't do much motorway work on my bikes, but it still feels long-legged enough for when the need arises.

Just thought I'd share my experience....

I wonder what will start niggling next: the indicator switch? the front brake? the flashers that don't? the upright riding position and lack of yellow half-fairing, clip-ons and rearsets? :roll:
 
Glad to hear it. The JPN I'm working on has a 22T front sprocket, but I figured it would be more useful and smoother with a 20 T. Also, a magazine test from '74 claimed the JPN came with a 20T. This bike using a 22T sprocket has a 100 link chain. How many links is your chain now with the 20 T sprocket?

Stu
 
+1 on the 20 tooth

I put a 20 on my 850 years ago, and like you I think it is perfect for our four speed boxes.

Turn signals and indicators, took them all off 20 years ago, even the speedo cable and drive.

Belt primary so zero leak primary and blessedly dry clutch plates.

Minimalist, less truly needed stuff, less to go wrong and fix.

Life is gooder when it is simpler.
 
74JohnPlayer said:
Glad to hear it. The JPN I'm working on has a 22T front sprocket, but I figured it would be more useful and smoother with a 20 T. Also, a magazine test from '74 claimed the JPN came with a 20T. This bike using a 22T sprocket has a 100 link chain. How many links is your chain now with the 20 T sprocket?

Stu
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Stu, I haven't counted, but I left the chain alone and the wheel is now just over halfway back in the swinging arm slots, so unless the chain is on its way out I'd guess it'll be OK as-is.
 
yes about 4k at 70mph ,cam working well, nice in the twisties, might be a different story in for long highway use.
 
Ratio's depend on the power band of engine and conditions and mood operates in.
My 2 Combat came with 19T which would be fine if I used in in city and some freeway travel or drag racing light to light. In rural area or turnpike travel 20T was about right for ~80mph cruise about 5000 rpm. Its also was low enough 4th gear climbed long grades w/o much extra throttle.
On my hot rod in her prime had almost 22T ratio with belt drive added. Kinda commitment leap to fully engage 1st, but great torque and rev range allowed wild flings in 2nd to almost 90 mph but 4th almost over drive like for below 5000 rpm 80's cruise. Also allowed Peel power to reach over 130 below 6000 where practical to do so. 850 2nd gear ratio is good upgrade for 750's, great passing canyon blasting gear and reduces rear skip on engine drag down shifts at speed.
Most useless gear is 3rd for me, not that great a passing gear yet too low to cruise.
 
Had a 21t on before the RGM belt drive upgrade and was great. With the belt drive the 21t 4th ran 70 mph at 3750rpm and 55mph was 3500 rpm in third. When for a 19t and it was good but a little too far the other way(tranny(sorry)gearbox loading). Got the 20t in now. 70 is 4000rpm in 4th and 3750 for 55 in 3rd. AHHHHH .....jusr right.

Now what to do with the 21t 520 and the 19t 520 gears? I'll be 57 in a month, I can't see goin back to the 19 and the 21 is just too high. Guess I will let em go. Virtually brand new. Hint, hint. Respond with pm so I don't get acused as a hijacker.
 
It's funny how everyone sees things differently. I now run a 23t and I absolutely love it. 70mph is 3500 rpm with plenty of grunt still. I always found the 750s undergeared with the 19 tooth and even the 850s not right at 21. First was always just for taking off and second wasn't much better. My old 850 lived in 3rd and 4th gears. Admittedly my bike has more low end and mid range than most but I'm very happy with the setup. It will still stomp the other local Nortons.

Vive la difference.
 
Encouraging report Fullauto, that grunt over rpms alone on tall gearing gives such good acceleration. Its about the only path open to Nortons d/t the crank whipper snapper. I'm trying to get a torque monster myself, not a hi rev wonder.
 
hobot said:
Encouraging report Fullauto, that grunt over rpms alone on tall gearing gives such good acceleration. Its about the only path open to Nortons d/t the crank whipper snapper. I'm trying to get a torque monster myself, not a hi rev wonder.
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Yep - my 850 is definitely a torque monster. I'd considered replacing the knackered cam with something more sporty, but pretty much everyone on the forum talked me out of it, and I'm glad I took the advice; it's got huge stump-pulling power, so can cope with wide ratios.
I prefer living in the 3-5k region, and where I live (Forest of Bowland, Lancashire) there are very few roads where lugging along at low revs in a high gear is viable, and I just wasn't using 4th very often.


This is a typical local road - narrow, twisty and 3-dimensional!
22T sprocket


It still revs well to 6k+ but it's most tractable below 5k, and it feels just great spending most of the time at around 3-5k.
By way of a comparison I took my Ducati out just after the last ride, and with a 5-speed box this is totally the opposite and really likes being revved (I think the 40mm carbs with accelerator pumps help here ;) ). It's a much faster bike, but the only reason it would be significantly quicker on local roads would be down to superior braking, rather than acceleration up to 80 or so.
 
That would explain your gearing choice. Mine lives between 2000 and about 4000 on a revvy day. I just don't feel the need to rev it. I've done about 130 miles today and as I was near home a modern, overpowered 4WD decided he was going to do me at the lights. It's quite funny revving to about 2500 to just stay in front and then to about 3500 in third and watch him drop back. Don't know what he was thinking.
 
I'm so glad to know I'm merely average in my Commando usage. Every bike I've run always seem to like 3500-5500 best for the vibe and good response. Harley to inline 4's, All just seem more pleasant and not much more to gain by almost red line shifting except more schizo-frantic sensations of hi freq vibes. I have to peddle my 6 speed bike to keep the pull going up to a bit over 110, I so love to slightly short shift the Norton to feel the longer stronger intervals of pull no each shift.
Basically what I've found is that torque is what gets ya going but hp does allows carrying on to higher speeds but not necessary faster to get to top out. Up to the top out of Commandos good ones can give about anything a run for the money up to 100 mph or so and often beyond that.

Peel's almost 22T ratio could run right up to 130-ish then had to tuck low and wait for more speed to creep up in straights. I may have gone a tad faster wtih tad lower ratio but might have lost the pleasant long legged easy going sensation.
I don't want it but do wonder if Nitrous oxide kit would be fun or dangerous in a mostly factory Commando geared on tall side.
 
Fullauto, just curious, if I remember correctly you run a single mikuni, single coil , elec ignition, the same as a lot of us, with the 23t sprocket does your bike want to pull much past 100mph or does it nearly go as fast in 3rd, I'm not rubbishing your choice just curious, I've seen some of the roads in oz a 20t could make for a long buzzy day.

ANDY, whats that kick start like??
 
splatt said:
ANDY, whats that kick start like??
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It's a lot better than the original, which was starting to swivel around on the splines a bit, but it lacks a positive location (detent or spring clip) when folded in, so it occasionally swings out a bit when out on the road. Freeing off the clutch is now essential (rather than just desirable) as otherwise it engages at about the 1 O'clock position. It does clear the downpipes by a country mile now - just the thing :wink:

Back to the subject of optimal rev range, I sold a Ducati 851 to fund the Commando, and that sounded just fantastic with that flat droning exhaust note above 6k.
Net result was I spent all my time going far too fast to be healthy :shock:
 
Good question Splatt. That is indeed my setup. As it stands, top is well overgeared and it will hit about 110mph. Third gear is about where fourth is on a 19 tooth 750. ie., about 17 mph per 1000 revs. I haven't tried it yet but best top speed I'm betting will be in third. I'm 800 miles and a couple of weeks into my Maney barrels and my engine builder is fanatical about running it in to his specs so I won't be giving it the berries until 1500 miles or so. Having said that, my bike still pulled like a train with a death rattle and badly scored pistons and bores from an early seizure on my last rebore. It is stronger now so it will be interesting. I do think however, that a single carb, with current manifold, loses out in the top end to a twin carb setup. I am quite happy with this just to have the simplicity of the single carb installation and lack of twin Anal, oops, I mean Amal, aggravation. I also rarely use high revs.
 
Fullauto said:
I'm 800 miles and a couple of weeks into my Maney barrels and my engine builder is fanatical about running it in to his specs so I won't be giving it the berries until 1500 miles or so. Having said that, my bike still pulled like a train with a death rattle and badly scored pistons and bores from an early seizure on my last rebore. ]


That would have to be disapointing , as I thought you rebored it when you first tried out the new head
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Correct. It would have saved me a lot of expense had he done what he was told to do and hone the +.040 bores and re ringed it. I don't believe in completely refurbishing stuff at the first hint of wear. It takes good usable life from components. As it was, I seized it within a couple of days doing what I thought was normal running in procedure. Hence two new sets of pistons, a set of Maney barrels and basically, a fully rebuilt motor.

Just got the bill in the mail today. Please buy more heads.
 
Fullauto said:
It's funny how everyone sees things differently. I now run a 23t and I absolutely love it. 70mph is 3500 rpm with plenty of grunt still. I always found the 750s undergeared with the 19 tooth and even the 850s not right at 21. First was always just for taking off and second wasn't much better. My old 850 lived in 3rd and 4th gears. Admittedly my bike has more low end and mid range than most but I'm very happy with the setup. It will still stomp the other local Nortons.

Vive la difference.
Click to expand...
Same here, have geared mine up to 18.2/1000 in top. Do quite a bit of M way work and it's still not high enough for decent 80 mph cruising. Was talking to a guy at a local meet the other night. He has a well lightened 850 single carb Commando with 24T and higher ratio in belt drive giving 20/1000. Claims he doesn't notice loss of accel. Mine is still 750 and I've probably gone as far as is practical. It's funny how some owners talk about the long legged nature of their bikes at normal legal crusing speeds......I've never found 4-4500 rpm long legged, you definitely know there's a lot going on down between the frame rails.
 
With a wide ratio 4 speed its a dilemma inside a dilemma.

The 19T was for 1/4 mile times and magazine bragging rights back in 1969 - 1971.
The 20T is good for around town and tight roads.
The 21T, IMO, is the proper all aroung cog.

I ran 20T at Streets of Willow in June and needed taller gearing to bridge the power band into and out of turn 3, floated valves trying, lost lots of time. Next time out I'll start with a 21T.
 
Interesting to see so many different takes on gearing here.

Apart from riding style preferences, the clear differentiator so far has been the nature of the roads being ridden on - and when I think about it, I'd much rather plan a route which excludes motorway work and maximises the use of roads more suited to riding a motorcycle - easier in some parts of the world than others, I'm sure!
Another factor which influenced my decision to lower the gearing was that above around 90 in top the acceleration is seriously deficient, and 4th amounts to an overdrive. I know the motor was recently rebuilt, but nothing beyond new rings, so it should pull a bit better than this; I guess this is why I wasn't using 4th much.
However, this is more than just a function of the bike itself...hopefully the photo may give a 'small' clue....

22T sprocket
 
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