Available engine performance

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Was a six speed Schafleitner gearbox for Manx in 1960 . Tho they wernt free .

To Tall first on 23 T = 130 @ 7000 gearing is the trouble . So a GOOD five or six speed with a modern stiff case etc & good steel , would be money well spent . an investment .
Mk III wouldnt even need the kickstart . ( If its got one :D )

Standard: 1st: 2.294, 2nd 1.755, 3rd 1.418, 4th 1.243, 5th: 1.1, 6th: direct
Low: 1st: 2.438, 2nd: 1.755, 3rd: 1.418, 4th: 1.243, 5th: 1.1, 6th: direct
Close: 1st: 2.169, 2ND: 1.69, 3RD: 1.418, 4th: 1.243, 5th: 1.1, 6th: direct

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QMCA6H​

Norton 6-Speed Gearkit​

Please confirm your application using the attached technical drawing before purchase.

In stock
POA
In stock

• Choice of mainshaft – 7R / G50, Manx, Dominator, Commando
• Standard or Reverse camdrum
• Includes ultra-lightweight magnesium cases
Gear Ratios
1st 2nd 3rd 4th 5th 6th
2.250 1.737 1.429 1.227 1.109 1.000


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Kiwi one'd be well proven . Dunno if the ' Mk II ' Amals are still around , but the 32 would flow what the works F-75 33 mm overbored Concentrics did .

Theres a poat here ( forum ) with a guy with Harley carb on a long 2-1 manifold . Weber / dellorotto 40 / 45 DCOE / DHLA are worth a look . Much finer metering,
give better deceleration / engine brakeing control , too . Sock air cleaners .

This below is basic factory ' kick it in the teeth ' road set up . for non Californians etc. But the better it runs , the cleaner anyway. more or less . bar idle .

scan0009-1-jpg.33761
scan0012-jpg.33764
scan0011-jpg.33763


Look up Rawlins here . Were the ' Works hot up mods from the bulliten . is in the back of the Clymer manual .
Ron wood , look up here . 70 Hp 750 dirt tracker . For guideance on priorities , for DURABILITY . even std .
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Not everybody drives the same on sundays .
Dew8KChVAAA_4RG.jpg


Soon as a cams in it, you notice the engagement speed in 1st . wet grass etc becomes demanding . Hence 5 speed ( or wide 6 . Gotta be bigger spead - wider , than stock . For the ROAD . )
 
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I wonder where a Triumph Bonneville T140 would have fitted on the graph.
And to complete the comparison, a Ducati and BMW
Would that complete the picture of common bike brands on our roads in the early seventie?
al
 
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Apr 13, 2021
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Good news!
Earlier in the thread I complained of my bike being a little breathless at higher power settings.
I have have just removed the carbs so I can spend a day looking for small parts on the floor like the mixture needle clip, and while I’m doing that also install new throttle cables. Low and behold I discovered the choke slide was not retracting all the way up, hanging down about half an inch into the throat when it should be fully retracted. That should make a bit of difference
Am I the only person to have trouble getting the mixture needle to enter the main jet with the carb in situ?
Al
 

Fast Eddie

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Well that means that you were only ever using a little over half throttle…

Resolving that is gonna make a huge difference.

Prepare to cancel all your tuning plans !!
 

SteveA

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The Kawasaki was light, as was the Commando.

In 1970 BSA were testing what would be the works 750 3 I expect against the power graph of an A65 twin with A10 crank and almost matching it. The twin had 78hp @ 7,000 at the crank. They were revving the 3 to 9,500 and still shy. And even a hot 650 A65 was beating it to 5,500rpm. The biking world would have been different if only the 3 cylinders were based on the A65. Thunderbolts have 27mm ports like the triple except they flow 108cfm each. If they used the Spitfire cam, same bore, short stroke for a 750cc, pushrods inside, with the oil, the motorcycling world would have been a different place. On the mildest hp calculator that flow would enable 77hp.

With A65 stroke and '71 porting for a 981 triple 87hp and massive torque would have decimated the Z1 with technology they had, and those heads can be made to flow enough for that to be around 120hp in a race motor with fierce mid range. Yet they chose a 500 Triumph base with ports crowded with head studs, as if BSAs development didn't exist. And no less than 4 external pushrod tubes and separate rocker boxes to leak oil which were so unnecessary, as was all the complex crank cases with the expense and time intensive assembly.

And the head of the BSA/Triumph company was thinking they needed OHC motors to catch the modern Japanese advances.
Now you are talking about what later tuners did to the Triples that means we Norton riders have real trouble keeping with them in classic racing!

I hope you weren't surprised that Triumph thought they knew better than BSA :cool:
 

SteveA

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Probably. I got it from the net. A friend has a LSR A65 with very high compression, it had a stock '71 head with 34mm TMs. Set records with it and got me to do a head which he is yet to test. But they were surprised at it's output, not top end, but grunt.

The head should extend top end and maybe add a little midrange. But I drew his dyno graph on this one for comparison. Remembering the dyno's are a bit different and the stock bikes had air filters and mufflers. But his bike really needed power peaking past 7,000 and I'm waiting to see a dyno graph with the new head and overlay it on the other graph when he gets to it. So this is with a stock '71 port.

In 68 BSA built a Spitfire with a specially ported head better in the bowl area. They used a 32 concentric for 56hp with 9-1 comp. The parts book showed a std head but it had it's own number. In 70 Umberslade's guys built a Firebird and I think used that porting and drawing, measuring 8hp or so difference with production line engines. A stock 71 head I have has that porting but with 30mm carb, it flows around 122cfm. That's what they were running for this red graph with 34mm carbs somehow adapted.



Lately I have been wondering if an A65 motor can be shoehorned into the BSA Fury (Triumph Bandit) chassis I have in place of the SR500 Yamaha engine that is in there!
 
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Lately I have been wondering if an A65 motor can be shoehorned into the BSA Fury (Triumph Bandit) chassis I have in place of the SR500 Yamaha engine that is in there!
Absolutely yes. Something really worth doing. People have done that. I so wish I had a frame. They suit a Thunderbolt cylinder head and they can give a lot of nice strong power because they can be made to flow well. With a 90degree crank they are very smooth with std 74mm stroke and can rev freely. The carbs can mount like this with a Thunderbolt head with twin carbs. Lots of stuff available steel rods, 5speeds, alloy big bore cylinders.

This is the head on my 650 Firebird.



This is a Triumph version.

 
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You might have missed it, but just above he has reported that the chokes were hanging halfway down in the carbs.
Now we can forget all the engine mods as the stock motor will do what it does best- rev easily to 6500 and provide enough torque to slide the rider off the big bench seat.
It might be good to change the thread title to " What's wrong with my Norton" or " Are there socks stuck in my Carbs?"

Glen
 

SteveA

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Absolutely yes. Something really worth doing. People have done that. I so wish I had a frame. They suit a Thunderbolt cylinder head and they can give a lot of nice strong power because they can be made to flow well. With a 90degree crank they are very smooth with std 74mm stroke and can rev freely. The carbs can mount like this with a Thunderbolt head with twin carbs. Lots of stuff available steel rods, 5speeds, alloy big bore cylinders.

This is the head on my 650 Firebird.



This is a Triumph version.

Nice looking bike, I am however averse to Triumphs generally. Actually I would be interested in a 650 Thunderbolt, one I had one once, two I think the single carb would fit easier into the frame space. Three, here in France there is a class that I can run my Fury in as a later 500 single or as a 650 twin!

I am in the process of converting it back from monoshock, which is needed for the class. As are wire wheels. Not the cast I have fitted, but I have built one wire wheel so far!
 
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I suspect a Commando 850 motor is fast enough for road use without modification. But it depends on how you want to use the bike. For cruising, the standard gearbox is good enough, but probably not good enough if you want to out-ride other guys around twisting roads. For about $700, you can buy a close ratio gear cluster and get much better performance. However if I was doing that to a road bike, I would use the standard Commando first gear and tolerate the gap between first and second.
I tried road racing my 850 with a standard gearbox - it was hopeless. With the close ratio 4-speed box, it was entirely different. My 850 actually accelerated fast enough to be competitive against 1100cc four cylinder bikes of the same era. When that big crank is spinning fast, nothing stops it - but you have to keep the revs high.
 
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Yes, I certainly have.
When it came out I was too young to get in and see it as it was R rated. Eventually I was able to sneak in to a theatre, I just loved it. It was an anthem to us. As a Northern Suburb Sydney boy I could recognise all the locations and when I somehow managed to buy a Yamaha TX 500 at 16 and 9 months (L Plate age), complete with custom paint and bikini fairing I was right there in my mind, through the bends of River Rd where many scenes were filmed.
Many rears later, perhaps the early 2000s, the producer of Stone visited our town (Bombala) to give a talk about the making of the movie and a special showing on the antique carbon arc projector equipmen. The story of how it was made, the cat and mouse battle with the police who were trying to prevent the street scenes wer unbelievable. The riders (A graders from Willoughby Motor Cycle Club had large 16mm movie cameras strapped to their helmet. The first time this had ever been attempted.
Also amazing was Kawasaki Australia’s unbelievable generosity and faith in the production in giving them unlimited access to brand new Kawasaki Z900 motorcycles. And they wrecked a few! It absolutely put that fine bike on the map in Australia
Of course the big road race between the policeman (Stone) on his Commando and the aboriginal bikie on a 900 was the highlight of the movie for me (barracking for the Norton of course) . At the last minute the Norton crashes and the Kwacker wins.
At the special showing the producer mentioned the possibility of a sequel (it never occurred) and tongue in cheek I asked him if he would get the riding scenes correct in the next movie. He asked what I meant and I quipped that the Norton should have won, with a wink.
A great movie!
al
I never liked Stone. Somebody was killed while it was being made. Motorcycle movies should inspire people to enjoy living. The most dangerous time to ride motorcycles is when you are a beginner. But on public roads, it is always dangerous.
 

Mart UK

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....For cruising, the standard gearbox is good enough, but probably not good enough if you want to out-ride other guys around twisting roads. ....
Riding with my mates around our country roads, I just stick it in 3rd and try not to brake. Seems to be working well, at the moment.
 
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Nice looking bike, I am however averse to Triumphs generally. Actually I would be interested in a 650 Thunderbolt, one I had one once, two I think the single carb would fit easier into the frame space. Three, here in France there is a class that I can run my Fury in as a later 500 single or as a 650 twin!

I am in the process of converting it back from monoshock, which is needed for the class. As are wire wheels. Not the cast I have fitted, but I have built one wire wheel so far!
Hard to get the same hp from a Triumph as a modified Thunderbolt headed A65. An 840 twin on methanol cannot match a 745cc A65 as yet, nor anything else including 1200cc Vincents, it runs on petrol but doesn't use a single carb. I guess it depends how fast you need it to go. It shouldn't need an engine bigger than 650 with a good head.
 

grandpaul

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I suspect a Commando 850 motor is fast enough for road use without modification. But it depends on how you want to use the bike. For cruising, the standard gearbox is good enough, but probably not good enough if you want to out-ride other guys around twisting roads. For about $700, you can buy a close ratio gear cluster and get much better performance. However if I was doing that to a road bike, I would use the standard Commando first gear and tolerate the gap between first and second.
I tried road racing my 850 with a standard gearbox - it was hopeless. With the close ratio 4-speed box, it was entirely different. My 850 actually accelerated fast enough to be competitive against 1100cc four cylinder bikes of the same era. When that big crank is spinning fast, nothing stops it - but you have to keep the revs high.
The spirit of hobot is strong in this one...
 

Chris

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The Bandit framed T140 looks like Tony Haywards old bike. Really nice bit of kit.
Just to play with this thread some more lol
Nige knows about this! Brought for a friend to relive his youth but he is to ill to buy it off me.
 

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