camshaft advice

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worntorn said:
Dan, that sounds like something else is amiss, not the cam.
The stock cam in an 850 revs and pulls very easily past 6500 as long as there are good twin carbs present and the exhaust is free flowing.

Here's one doing just that.
There's no sense of any fall off after 5000, in fact you need to be careful to avoid going past redline.

To 6500 in 1st and 2nd



Glen
Click to expand...

1st and 2nd gear will tell me little about the true torque output. I always tuned my 86 inch Stroker Panhead in 3rd gear. (4th would have gotten me above 130 MPH in 4th)

I also learned about parasitic loss when the ambient temperatures dropped in autumn from running high viscosity oil that way.

I do plan on checking the jetting when I get the layshaft bearing replaced over the winter.
 
What diameter are the exit holes?
There are at least two versions.
The small hole ones would probably shoot air (or peas)further than the big hole.
One other question, which CS sprocket is in place?

Glen
 
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Dan1950 said:
1st and 2nd gear will tell me little about the torque output
Click to expand...
It just gives you something to do a quick comparison with, another Norton 850 rather than your memory of the Harley .

Does your bike rev out about that quickly in those gears?
If so there's probably nothing wrong with it and you need to spend $ if you would like more performance.

Just trying to help here.

Glen
 
worntorn said:
What diameter are the exit holes?
There are at least two versions.
The small hole ones would probably shoot air (or peas)further than the big hole.
One other question, which CS sprocket is in place?

Glen
Click to expand...
From the revs at speed it is probably a 20T sprocket. The exit holes in the mufflers appear to be quite large. It barks with authority.
 
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worntorn said:
It just gives you something to do a quick comparison with, another Norton 850 rather than your memory of the Harley .

Does your bike rev out about that quickly in those gears?
If so there's probably nothing wrong with it and you need to spend $ if you would like more performance.

Just trying to help here.

Glen
Click to expand...
After coming on strong at 4000 RPM, It falls on its face > 5000 RPM in 3rd and 4th. I've been hot rodding for over 50 years starting out with a 301 SB Chevy (283 bored .120" over) A65T bored .080" over with 10.5:1 pistons. 2006 Dodge Daytona running 12 flat N/A @ 4300# with a stock 5.7 rotating assembly, etc, etc.

I know when an engine is not pulling the torque it should.



And it got 2 MPG better fuel economy on the highway than it did stock.
 
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All that hot rodding experience is cool, but I think Glens point is, are you comparing apples with apples. After years of riding your hotrod Pan, it’s kinda understandable that a stock old Norton is gonna feel a bit flat.

So, it could easily be that what you’re feeling is the torque level off, yes the hp continues to rise, but not so steeply. When I road my mates near stock 850 (with peashooters) I was indeed surprised how well it revved… but those revs did not seem to translate into very impressive pull or continued rate of acceleration. Therefore, it could be the case that it is as good as it gets, and if you want more, you gotta get your wrenches and wallet out!

Conversely, the bike is old, and you’ve not had it long, there is a very long list of things that are quite probably not ‘perfect’ regarding its state of tune (as you’ll know very well), so it’s possible that just getting it all ‘right’ will get the bike where you want it to be as Glen alluded to earlier.

But, with a history like yours as a habitual hot rodder, my money is on you not being happy leaving this bike alone! Just be careful though, it can be a long, steep, expensive slippery slope (yeah, I know)!
 
Fast Eddie said:
All that hot rodding experience is cool, but I think Glens point is, are you comparing apples with apples. After years of riding your hotrod Pan, it’s kinda understandable that a stock old Norton is gonna feel a bit flat.

So, it could easily be that what you’re feeling is the torque level off, yes the hp continues to rise, but not so steeply. When I road my mates near stock 850 (with peashooters) I was indeed surprised how well it revved… but those revs did not seem to translate into very impressive pull or continued rate of acceleration. Therefore, it could be the case that it is as good as it gets, and if you want more, you gotta get your wrenches and wallet out!

Conversely, the bike is old, and you’ve not had it long, there is a very long list of things that are quite probably not ‘perfect’ regarding its state of tune (as you’ll know very well), so it’s possible that just getting it all ‘right’ will get the bike where you want it to be as Glen alluded to earlier.

But, with a history like yours as a habitual hot rodder, my money is on you not being happy leaving this bike alone! Just be careful though, it can be a long, steep, expensive slippery slope (yeah, I know)!
Click to expand...
Probably cheaper than a 301 SB Chevy (283 bored .120" over)
 
I have a JS0 in my 850. Naturally I always think I should have gone to a JS1!
But I think most of us just cannot rebuild a bike without "improving" it. Just
how it was back in the day but now it is rather foolish. So many bikes are faster
than even a leaned on Commando not to mention the cars.
Instead go for a good easy to ride and reliable stock bike. If you need to go fast,
easier cheaper and safer to just cop a modern bike.
...and don't forget that the petrol is increasingly expensive and hard to find in the
higher octanes.
 
Onder said:
I have a JS0 in my 850. Naturally I always think I should have gone to a JS1!
But I think most of us just cannot rebuild a bike without "improving" it. Just
how it was back in the day but now it is rather foolish. So many bikes are faster
than even a leaned on Commando not to mention the cars.
Instead go for a good easy to ride and reliable stock bike. If you need to go fast,
easier cheaper and safer to just cop a modern bike.
...and don't forget that the petrol is increasingly expensive and hard to find in the
higher octanes.
Click to expand...
I don’t agree.

It’s not about going fast, it’s about having FUN.

Of course it’s easier and cheaper to find a modern bike that is faster, but it’s difficult staying awake, they’re so dull.

A thrash on a raw, mean, hot rodded Brit bike gets the blood and Adrenalin flowing and reminds you that you’re ALIVE !!

(An increasingly rare and precious feeling in this day and age IMHO !!)
 
And yes… you should have gone for the JS#1

but both the Commando and the Trident invite rorty riding and as we age it is probably better to keep the odds in your favour.
I have fun on the old Interceptor and am less tempted to pass.
 
Dan1950 said:
When displacement is increased it effectively reduces the potency of the cam profile. What would be a "hot cam" in a 650 would not have the same torque profile in an 850. I'm finding the torque fall off above 5000 RPM a bit disappointing in my '74 MK II 850. I'm thinking a profile that delivers less cylinder pressure at low RPM might perform very nicely in my 850 with a mild compression increase. More overlap would effectively reduce dynamic compression at lower RPM allowing a bit of "cushion" for lower octane fuels at 10:1 static CR. I had a similar cam profile in 86 Cu In Panhead with 10.5:1 static CR. I could start it with my hand and it would survive on 87 octane fuel as long as I didn't lug the engine. It would come on like a freight train at 3500 RPM and pull strongly to the 5500 RPM shift points.
Click to expand...
Mint 850 not so much then?

If you want to feel some serious pull above 5000 RPM, my experience says the stock cam is the not the ticket regardless of what historical tales are being told. A stock cam should not fall on it's face above 5000 RPM though. It's not the cam causing the issue, unless it is worn flat.

You can tune a Norton with a 2S profile cam to run very well on the street and pull the grips out of your hands at 5500RPM. But you probably aren't going to do it with a stock Norton head, a stock cam, and little Amal carburetors. You can build a good grocery getter with stock parts, but nothing particularly quick.

Forget about what the Harley did. A V-twin doesn't map very well to a de-tuned twin cylinder thumper Norton 850.
 
Ah the 2s legend
I've never ridden a bike that pulled the bars out of my hands.
160 HP doesnt do it but maybe 65 would.:)

Glen
 
Fast Eddie said:
I don’t agree.

It’s not about going fast, it’s about having FUN.

Of course it’s easier and cheaper to find a modern bike that is faster, but it’s difficult staying awake, they’re so dull.

A thrash on a raw, mean, hot rodded Brit bike gets the blood and Adrenalin flowing and reminds you that you’re ALIVE !!

(An increasingly rare and precious feeling in this day and age IMHO !!)
Click to expand...
Yes, it’s not cheap or easy, but the rewards of doing it are considerable. Perhaps I’m fooling myself but I think the kick from riding a tweaked Commando is difficult to get from a modern “push button and go” bike
 
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