2S Cam into an 850

It's how the gear box is used and how you use the extra torque from running a hot cam, in 1979 my layshaft bearing blew before the Featherbed conversion as well a few bushers replaced but a few years later my kick start shaft broke at the pawl end from a shop welding my lose kicker on the shaft (unkown to me at the time but 2 weeks later it broke), was in the shop to work out a misfire problem at the time, my Norton has never been to a shop since that was 1983, since then with the work done to my motor I have only been in my gearbox 4 times to replace the worn kick start pawl but the last time I replaced it I replaced the kick start gear where the pawl engaged the gear, it was worn, that was 30+ years ago and I haven't been it the GB since.
I use the torque of my hot motor smartly and don't flog the gearbox (use too in my younger days) 2nd and 3rd gears are used most for high revving and using the torque of my motor but as I say I do it smartly and after 47 years my gearbox still shifts smoothly and just clicks in too neutral if the clutch is set right, I still run my original clutch plates that my bike came out of the factory.
If you don't flog the GB it will work fine but in my younger days from 1976 to 1979 young and silly my GB copped a flogging with many burnouts and racing everything on the road lol and had a lot to prove to all my mates who rode jap bikes that the Norton wasn't no slouch and sounded so much better.
To Al I just didn't put a hot cam in my motor crank, rebore to tight tolerances, ports/manifolds, jets, ignition and open exhaust system from made to fit headers to open mufflers with just enough baffle in it for a bit of back pressure, I can run quietly when putting around but open the throttle up it comes alive and loud with a sweet sound from my motor, I did it right from day one of the conversion to the Featherbed but over the years I upgraded a few things to make it even better, my Norton has always been a sweet running bike since the conversion in the early 80s (I had a lot of problems from 1976 to 1979 when it was all Commando, from ignition to carbs) after the conversion in 1982 with new carbs and new ignition system my Norton has been good, whether I been lucky or I have a freak of a Norton with only a few minor fault in the 42 years since I built the hot 850 Featherbed, so without much experience in building my first hotrod Norton I did something right as I have a sweet running Norton.

Ashley
 
Deckard said:
A belt drive primary is greatly appreciated by the transmission.
Click to expand...
Until they fail, I went the belt drive way and it was good for the first 3 years then started to have problems with run off (and yes I run 2 adjusters) so after 5 years I went back to chain drive in the primary and solved a lot of belt problems and really I think the chain is so much better (in my opinion), but my next chain replacement will be a duplex chain from the Chainman, if a primary chain is adjusted right as well rear chain they will get long trouble free life, a chain has a little more give and is smooth as a belt drive if adjusted right.
 
ashman said:
It's how the gear box is used and how you use the extra torque from running a hot cam, in 1979 my layshaft bearing blew before the Featherbed conversion as well a few bushers replaced but a few years later my kick start shaft broke at the pawl end from a shop welding my lose kicker on the shaft (unkown to me at the time but 2 weeks later it broke), was in the shop to work out a misfire problem at the time, my Norton has never been to a shop since that was 1983, since then with the work done to my motor I have only been in my gearbox 4 times to replace the worn kick start pawl but the last time I replaced it I replaced the kick start gear where the pawl engaged the gear, it was worn, that was 30+ years ago and I haven't been it the GB since.
I use the torque of my hot motor smartly and don't flog the gearbox (use too in my younger days) 2nd and 3rd gears are used most for high revving and using the torque of my motor but as I say I do it smartly and after 47 years my gearbox still shifts smoothly and just clicks in too neutral if the clutch is set right, I still run my original clutch plates that my bike came out of the factory.
If you don't flog the GB it will work fine but in my younger days from 1976 to 1979 young and silly my GB copped a flogging with many burnouts and racing everything on the road lol and had a lot to prove to all my mates who rode jap bikes that the Norton wasn't no slouch and sounded so much better.
To Al I just didn't put a hot cam in my motor crank, rebore to tight tolerances, ports/manifolds, jets, ignition and open exhaust system from made to fit headers to open mufflers with just enough baffle in it for a bit of back pressure, I can run quietly when putting around but open the throttle up it comes alive and loud with a sweet sound from my motor, I did it right from day one of the conversion to the Featherbed but over the years I upgraded a few things to make it even better, my Norton has always been a sweet running bike since the conversion in the early 80s (I had a lot of problems from 1976 to 1979 when it was all Commando, from ignition to carbs) after the conversion in 1982 with new carbs and new ignition system my Norton has been good, whether I been lucky or I have a freak of a Norton with only a few minor fault in the 42 years since I built the hot 850 Featherbed, so without much experience in building my first hotrod Norton I did something right as I have a sweet running Norton.

Ashley
Click to expand...
Do you still have the taper roller bearing fitted to the layshaft?
 
Another gearbox stress on 850s was going from a 19T gearbox sprocket to a 21T.
Add the 1A/2A taller second gear and 22T sprocket on non-US models...
 
Deckard said: "A belt drive primary is greatly appreciated by the transmission."
I used to think that too.
But I now believe that a belt drive is as hard on the gearbox as a primary chain. Ie, a belt drive has no more stretch or shock absorption than a chain.
Comments?
 
Stephen Hill said:
Deckard said: "A belt drive primary is greatly appreciated by the transmission."
I used to think that too.
But I now believe that a belt drive is as hard on the gearbox as a primary chain. Ie, a belt drive has no more stretch or shock absorption than a chain.
Comments?
Click to expand...
IMO it is pointless to debate the Cush effects of chain vs belt as even if one is better than the other, the effect is inconsequential.

Personally, I do not believe that the theoretical cushioning a chain provides is a realistic factor in this application with such a short chain.

This ‘hard’ poly type belts appear to offer zero Cush to my eye. The rubber belts claim to offer some Cush, but again IMO (even if true) the amount provided renders it inconsequential.

The main benefit of a belt IMO (as discussed recently elsewhere) is the huge weight saving on the mainshaft that is possible when running a belt and the consequent reduction in stress and load on that mainshaft and what it connects to.

So, the main benefits to a belt IMO are:

1. Reduced weight, stress and load on the mainshaft.

2. A dry clutch.

Of course, these are only ‘benefits’ if the owner views them as such. As an ex ‘Johnny Racer’ type, I am biased towards the benefits of a belt.

At the end of the day, both systems (if installed correctly) function perfectly well.

Different owners seek different benefits.

Unto each his own.
 
B+Bogus said:
Another gearbox stress on 850s was going from a 19T gearbox sprocket to a 21T.
Add the 1A/2A taller second gear and 22T sprocket on non-US models...
Click to expand...
With a close ratio gear box, there is less load on the internal gears because they all spin faster -except when first gear is too high. That is the reason we need six gears, close ratio. The other thing is - the throttle response problem disappears. A TTI gearbox might cost less than a Full Auto cylinder head - which would you buy first ?
For performance, the TTI box wins hands down.
The Japanese are not stupid. Two things - needle jets and gears - are the way to get performance. Most of their bikes are neutral handling - so can be beaten. The transition point from braking to accelerating needs to be very early in corners - more trail. When you increase the trail, the transition point advances and the lean decreases. You can put more power on the ground. Use a steering damper.
 
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acotrel said:
With a close ratio gear box, there is less load on the internal gears because they all spin faster -except when first gear is too high. That is the reason we need six gears, close ratio. The other thing is - the throttle response problem disappears. A TTI gearbox might cost less than a Full Auto cylinder head - which would you buy first ?
For performance, the TTI box wins hands down.
Click to expand...
No argument from me regarding the benefits of a TTI gearbox, but keeping it in context I was referring to unmodified production bikes.

The layshaft bearing is - to me, at least - the only essential modification required on my Nortons.
Changing down from second to first on my Mk2A used to make me cringe until I remembered to let the revs drop right down before downshifting
 
Fast Eddie said:
IMO it is pointless to debate the Cush effects of chain vs belt as even if one is better than the other, the effect is inconsequential.

Personally, I do not believe that the theoretical cushioning a chain provides is a realistic factor in this application with such a short chain.

This ‘hard’ poly type belts appear to offer zero Cush to my eye. The rubber belts claim to offer some Cush, but again IMO (even if true) the amount provided renders it inconsequential.

The main benefit of a belt IMO (as discussed recently elsewhere) is the huge weight saving on the mainshaft that is possible when running a belt and the consequent reduction in stress and load on that mainshaft and what it connects to.

So, the main benefits to a belt IMO are:

1. Reduced weight, stress and load on the mainshaft.

2. A dry clutch.

Of course, these are only ‘benefits’ if the owner views them as such. As an ex ‘Johnny Racer’ type, I am biased towards the benefits of a belt.

At the end of the day, both systems (if installed correctly) function perfectly well.

Different owners seek different benefits.

Unto each his own.
Click to expand...
The main benefit of the single row primary chain on my bike, lies in the ease of changing the overall gearing. My drive sprockets are cheap JAWA speedway items which sit on a splined carrier and float to give alignment with the Manx clutch on the Commando length gearbox mainshaft.
If I had primary drive as a belt, changing the gearing for different circuits would have to be done by pulling the rear wheel out and adjusting it afterwards. Rear sprockets are much more expensive. In the olden days Phillip Island required the highest gearing. It was usually down one tooth on the engine sprocket for Calder and down another for Winton or Mount Gambier.
My Seeley 850 runs much higher gearing than I would have expected. I did not change it between Winton and Mount Gambier. With the strange motor, the close ratios work better with the high overall gearing.
 
" A fun read tho, even if it's fiction! " wotcher needis the ORIGINAL M C M report / anaylisis . Ran a slick gearing for the ' low times ' or was it a Dunlop Road race tyre ! KR 53 or something .
with the little round holes innit . Covered the full baloney , step by step , as it were , almost . ANYONE GOT IT hiding somewhere ? Motor Cycle Mechanics . Was ineligable for production due to emmisions ,
according to dennis poore .

NIEN .
2S Cam into an 850


the WAY one approaches it , does help . You tend to get the clutch / mainshaft - twang and bounce - on a hot ' powershift ' , with a touch of clutch , punched through ,
when the throttles eased only for a micro second , at full output . Foist to 2nd , where it'll skip & squeal the rear . WITH all the weight - ON IT . U n d e r w a y .

a Bit of a LOAD , full bore & rpm's / here and there . De Cammed mine held a XS 11 . ( 750 ) 2S was way more vicious . Tho the particularly refined and adept rider
obviously was a key factor .

ALSO pommy riders tend to be lighter , if theyre not well fed , like Americans .

2S Cam into an 850
 
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NORTON Service Release N3/29 and N3/64

So we're told .

the 64 , near the end , here . file:///C:/Users/Patrons/Downloads/Norton%20Commando%20Service%20Sheets%20(indexed).pdf
( thow that in search , should gedditt . ) google soich or suchlike . AWESOME for minuate .
file:///C:/Users/Patrons/Downloads/Norton%20Commando%20Service%20Sheets%20(indexed).pdf
The M C M ?? artical , and was a briefer U S mag report , and Drag Strip run , gave a bit of colour & development info .

Eeeh , by guum . https://www.tioc.org/partsbooksnorton/sb-nort-Stage One High Performance N3:73.pdf

running 11-8 (2 ) at 114 . there .
 
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Matt Spencer said:
NORTON Service Release N3/29 and N3/64
Click to expand...
Some good information there!
I think the Norton drawing checker needs a kicking though - since when did .095" equate to 1.27mm?
Quite important when skimming the head, I would have thought....

Norman White had the perfect credentials for showing the Cycle World journalists how the Combat standing quarter times were obtained

Superbike 7, March 1970 Cycle Magazine performance test

I searched before posting, couldn't find a duplicate post of this. This should be readable online by expanding the pages. It will be of interest to any Commando owner who hasn't already read the article. Why do we always hear that the Honda 750 was the first Superbike, or the Triumph/BSA...
www.accessnorton.com www.accessnorton.com
 
The Combat standing quarter times in my collection of road tests were the same +- as the earlier 750s, all in the low 13 second range, all fitted with 19 tooth. It's not surprising given DynoDave's observations on the crudeness of Combat head porting.
It seems that , for acceleration at least, whatever gain was found with increased compression and hotter cam was offset by the bad porting.

The first two 850s tests were a shade quicker, high 12s and fitted with 20 tooth.
Then the silencers were changed to very restrictive type in order to satisfy California rules. Performance went away.

Today California is the land of earsplitting open pipe Harleys.

Glen
 
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I suggest it does not matter much what gearing is used on a Commando. If is high geared and the heavy crank is spinning at 6000 RPM - when you drop the clutch, the bike will jump. For maximum acceleration, close ratios are needed. If the motor revs continually at about 6000 RPM, and you are using lean taper needles in the carbs, that is the quickest. The slightest bit rich is always slower. The problem is - how do you know when your jetting is that bit too rich, without doing damage ? - When you jet that critically, you have to contend with the weather. Amal carbs probably cannot get the best out of petrol. You would need needle jets in internal dimension increments of a quarter of a thou of an inch. With Amal, they come in thousandths increments. And who tries different tapered needles anyway ?
Many people seem to believe that more fuel means more power. If you are jetted too rich, raising the compression ratio or advancing the ignition can give more power. The three things are in balance. Best power is just before you start doing damage. When you use wide ratios, you lose more vacuum on up-changes, so you need richer tapered needles, The whole thing can become self-defeating.
 
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When you build a race bike, you need three things - , the frame, a front brake and a gearbox. Most motors are fast enough without doing much.
 
A squid eating dough in a polyethylene bag is fast and bulbous, got me?
 
  • Haha
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acotrel said:
I suggest it does not matter much what gearing is used on a Commando. If is high geared and the heavy crank is spinning at 6000 RPM - when you drop the clutch the bike will jump
Click to expand...
Gearing most definitely does make a difference to acceleration.
In the collection of Commando period road tests, the 750s with 19 tooth are all in the low 13 second range. 20 tooth are all mid to high 13 seconds. The only 21 tooth run at the strip went just over 14 seconds.

Uk Sprint racer Roy Robertson advised me to gear the bike such that the max bhp rpm in top gear= 1/4 mile terminal speed. Overgearing or under gearing will produce a slower 1/4 mile result.

Glen
 
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