Camshaft choice - especially 2S

worntorn said:
He has switched his fuel injected big valve 924 back to the stock profile cam.
Apparently that gives the strongest midrange power of all the available profiles. It will also be the easiest on valve gear.
It says a lot about Doug Hele's abilities that with all of the decades since and multiple attempts to get the magic cam profile for a hot road going Norton twin, for both durability and good road performance, Doug Hele had already drawn the thing in 1960.

Glen
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My first season of racing was with a standard 1970 Fastback Commando motor. Standard '650SS' road cam, 28.5mm ports 30mm carbs. Excellent package, for road and novice racer.

No worry about exceeding 7500 because it went into valve float at 7200! (Typically end of the Revett straight at Snetterton on a 19Tooth front sprocket!)
 
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I'm sure that when Doug Hele designed the cam for the 650ss he had no idea that it would later be used on 920cc Nortons and would work well there too.
I believe Ken has also used the standard profile for his 1007 road bike. It will be interesting to see how that works out.

Aside from the different requirements in road vs race, there is also the question of riding style and choice of roads.
If you like touring in the mountains then big midrange is really useful.
If you enjoy a hooligan ride then a cam that gives a bit more at top could be more fun, even if the midrange is reduced. The increased wear might not matter if the bike is only going to do 5000 miles in ten years, then the owner is off to the Help Me Home:)
Depressing thought, I think I'll try riding the Maico to keep the old man out!


I believe this is all on topic, judging by the thread title?​

Glen
 
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worntorn said:
I'm sure that when Doug Hele designed the cam for the 650ss he had no idea that it would later be used on 920cc Nortons and would work well there too.
I believe Ken has also used the standard profile for his 1007 road bike. It will be interesting to see how that works out.

Aside from the different requirements in road vs race, there is also the question of riding style and choice of roads.
If you like touring in the mountains then big midrange is really useful.
If you enjoy a hooligan ride then a cam that gives a bit more at top could be more fun, even if the midrange is reduced. The increased wear might not matter if the bike is only going to do 5000 miles in ten years, then the owner is off to the Help Me Home:)
Depressing thought, I think I'll try riding the Maico to keep the old man out!


I believe this is all on topic, judging by the thread title?​

Glen
Click to expand...

Take the Maico up Dyno Hill. I'm sure your neighbors would appreciate it maybe early on a Sunday morning. :)

I thought the OP didn't want to hear about anything other than the 2S. Probably confused this 2S post with his other 2S post.

As Jim mentioned his JS2 is similar to the 2S, PW3, yada yadda, but has smoother ramps and is not hard on the valve train. Both the 2S and JS2 work better with higher compression, and if one is going to ride a lot in the mountains 19-42 final gearing works well with either cam. I geared my Norton way up though because droning at high RPM on the HWY to get to someplace where I can use my engine was driving me batty so I geared it up. Disadvantage is I can't be lazy with the gear selection in an AMC gearbox climbing. Hoping to fix that to some degree with a 5 speed where I might be able to get away with using 3rd gear and the taller final 21-42 gears in the steeper climbs.

Anywho, it's cheaper and easier to build and run stock by a long shot. There's no advantage in building a race engine for the street other than personal satisfaction of doing it.
 
Schwany said:
Take the Maico up Dyno Hill. I'm sure your neighbors would appreciate it maybe early on a Sunday morning. :)

I thought the OP didn't want to hear about anything other than the 2S. Probably confused this 2S post with his other 2S post.

As Jim mentioned his JS2 is similar to the 2S, PW3, yada yadda, but has smoother ramps and is not hard on the valve train. Both the 2S and JS2 work better with higher compression, and if one is going to ride a lot in the mountains 19-42 final gearing works well with either cam. I geared my Norton way up though because droning at high RPM on the HWY to get to someplace where I can use my engine was driving me batty so I geared it up. Disadvantage is I can't be lazy with the gear selection in an AMC gearbox climbing. Hoping to fix that to some degree with a 5 speed where I might be able to get away with using 3rd gear and the taller final 21-42 gears in the steeper climbs.

Anywho, it's cheaper and easier to build and run stock by a long shot. There's no advantage in building a race engine for the street other than personal satisfaction of doing it.
Click to expand...

JS2 cam and 9.5:1+ compression pulls 22-42 gearing to the point where I wish I had a 23 up front on the 850. It also cruises on the freeway with ease. Cylinder head and intake port size is more of the limiting factor. A 19 tooth front sprocket really limits your riding and distance you want to take the bike. I would rather have more compression and a js2 cam to have a more versatile bike that still feels like a Norton.
 
maaseyracer said:
JS2 cam and 9.5:1+ compression pulls 22-42 gearing to the point where I wish I had a 23 up front on the 850. It also cruises on the freeway with ease. Cylinder head and intake port size is more of the limiting factor. A 19 tooth front sprocket really limits your riding and distance you want to take the bike. I would rather have more compression and a js2 cam to have a more versatile bike that still feels like a Norton.
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I get that. I wasn't talking about what I like in a Norton engine, merely what is usable and cheaper to put together in terms of time and cost.

Nice that you could use 23-42 gearing on the street and still climb over something like Ebbetts pass on CA Hwy 4. I doubt I'd ever get out of 2nd over Ebbetts, but haven't ever done it on a Norton so not sure. I have taken lots of other bikes over Ebbetts though. Tight like a tiger.

I like my Norton engine with the JS2 cam, some other performance-oriented parts in it, and the 21-42 gearing out back. The engine did seem to have a little more umph when it had a little over 10:1 compression. It's closer to 9:1 now though. Still runs well. I have thought about a 22T sprocket on the gearbox, but don't need more gear myself.
 
Schwany said:
I get that. I wasn't talking about what I like in a Norton engine, merely what is usable and cheaper to put together in terms of time and cost.

Nice that you could use 23-42 gearing on the street and still climb over something like Ebbetts pass on CA Hwy 4. I doubt I'd ever get out of 2nd over Ebbetts, but haven't ever done it on a Norton so not sure. I have taken lots of other bikes over Ebbetts though. Tight like a tiger.

I like my Norton engine with the JS2 cam, some other performance-oriented parts in it, and the 21-42 gearing out back. The engine did seem to have a little more umph when it had a little over 10:1 compression. It's closer to 9:1 now though. Still runs well. I have thought about a 22T sprocket on the gearbox, but don't need more gear myself.
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Your talking my road! Can't count the number of times I have been up it. It's a slow road and second gear is ambitious for most of that road and altitude really plays with the bikes power. For sure an outlier road, you picked the right road to connect your point with me. The Commando with 21-42 gearing is the bike to get you to Ebbits pass, but you wish you had a Triumph, BSA, or Atlas once you get on the pass. Once you clear the pass the roads go back to being well suited for the Commando.
 
I would agree that with any other motor than a Norton twin, a lumpy cam is usually better. But the heavy crank makes it different from other motors. You end-up with a throttle response problem unless you use close ratio gears. Also the standard crank balance factor stops you from revving the motor to the level at which the cam begins to work. What I have always liked about race cams is the adrenalin rush as they come on song. A Commando motor cannot be used in the same way as most others. However the heavy crank can be used to advantage. As cams go, the standard cam in an 850 is a hot cam. However in a normal set-up, it cannot be used in the same way as in other motors.
What flywheel is used in the P11 and N15 - is it the same as in an Atlas ? Commando cranks were probably designed to make motors idle without rocking the bike backwards and forwards in dealers' showrooms.
If you look at the history of Norton twins - the 650ss was the first sports' bike. Then there was the Atlas. But sports' bikes have never been much good for road use. A CB750 Honda does not give you much of an adrenalin rush. I rode one when they first arrived - it felt dead.
I suggest the simplest way to get a Commando really going would be to buy a 6 speed TTI gearbox, and replace the flywheel. - Total cost about $6000 Australian dollars.
 

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