Commando HP and Torque

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baz said:
The point I am making is these myths and rumours come from back in the day when the bikes were brand new and standard
I suspect a stock (black cap equipped) MK3 commando would be slower and heavier than a stock combat 750
But with a set of pea shooters I think it'd be a different story
It is all a bit of fun
Click to expand...
Can't much tell the difference from when I ran the Black caps and then changing over to the peashooters. So much for advice.
 
I tested some original Norton black caps on Dyno hill. They sapped the power bigtime.

Glen
 
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baz said:
The point I am making is these myths and rumours come from back in the day when the bikes were brand new and standard
I suspect a stock (black cap equipped) MK3 commando would be slower and heavier than a stock combat 750
But with a set of pea shooters I think it'd be a different story
It is all a bit of fun
Click to expand...
Yes, exactly.

In 1977 no after market e starts were available for 750s, so the fact is the MK3 was the heaviest Commando of the line.

And they came with black caps, which even Glen admits ‘sap power’.

Some of these changes that added weight and sapped power happened gradually, but they all culminated on the MK3.

So… as offered to the public, in unmodified form, the MK3 was both heavier and slower than early 750s.

So in 1977, it was true that the MK3 was the heaviest and slowest Commando ever.

What annoys Glen is that people still believe it’s true today, but if the MK3 has been fitted with peashooters, and the 750 an E start, then they‘ve actually ‘levelled up’.

What was fact in ‘77 is folklore in ‘22 !
 
Thing is, in this traffic infested, speed camera festooned septic isle we live in, ANY bike (even a 'gutless' B/C equipped Mk3) is more than adequate for getting from A to B as quick as... assuming you want to stay fine free and with a clean license :-)

Of course on the Norton you'll arrive in style!
 
EstuaryBoy said:
Thing is, in this traffic infested, speed camera festooned septic isle we live in, ANY bike (even a 'gutless' B/C equipped Mk3) is more than adequate for getting from A to B as quick as... assuming you want to stay fine free and with a clean license :)

Of course on the Norton you'll arrive in style!
Click to expand...
How does a man defend black caps… and also own a hooligan P11 !!

I assume one belongs to Dr Jekyll … and the other to Mr Hyde ?? ;)
 
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Mr Hyde?? Doesn't he play the Trumpet??

At the risk of thread derailment (so what's new?), for me, it's not strictly about the numbers... 'adequate' is enough :-)
But, and I'm sure many 'petrol heads' will get this, did you ever see a brochure/photo etc of a machine and think: 'YES!!'
I've got the NVT Mk3 brochure and that red Mk3 Roadster hit the spot here, as did a Classic Berk photo of a G85CS many moons ago.
For me, black caps are part and parcel of that bike's style, as peashooters are to earlier bikes. I know people put rayguns on T160s but to me that's an optical mismatch as well....

'Nuff said, so I will now ride off into the sunset....... slowly and quietly :-)
 
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EstuaryBoy said:
Mr Hyde?? Doesn't he play the Trumpet??

At the risk of thread derailment (so what's new?), for me, it's not strictly about the numbers... 'adequate' is enough :)
But, and I'm sure many 'petrol heads' will get this, did you ever see a brochure/photo etc of a machine and think: 'YES!!'
I've got the NVT Mk3 brochure and that red Mk3 Roadster hit the spot here, as did a Classic Berk photo of a G85CS many moons ago.
For me, black caps are part and parcel of that bike's style, as peashooters are to earlier bikes. I know people put rayguns on T160s but to me that's an optical mismatch as well....

'Nuff said, so I will now ride off into the sunset....... slowly and quietly :)
Click to expand...
I agree 'cept for, you can't beat a pair black caps with the internals ripped out :cool:
 
cash said:
I agree 'cept for, you can't beat a pair black caps with the internals ripped out :cool:
Click to expand...
There are straight through (perforated absorption tube) one’s available, the ones I’ve heard sound great, throaty without being harsh.
 
Whatever exhaust system you use, the valve timing and the jetting must be optimised to suit it..
Just changing the mufflers and nothing else does not usually achieve much. And the other thing is, the exhaust system can change the way the bike pulls. If you gain an increase in torque, you often do not realise it until you raise the overall gearing.
When I first raced my 500cc Triton, it had separate exhausts with large diameter megaphones. It had tons of top end and woulf rev easily to 10,500. I fitted a more restrictine 2 into 1 system and Immediately lost 2000 revs off the top, but I started getting better lap times. As I started cotting the outlet of the collector back and fitting bigger tail pipes, I regained a lot of the top. At the same time, I played with re-timing the exhaust cam and changing the jetting. It took a while to find a good combination.
If you fit open megaphones to a road going Commando without jetting up, you would probably burn a piston, unless you were already jetted too rich. When you fit different silencers, if a less restrictive one gives better performance, you were probably previously jetted a bit rich. Getting the mixture correct is critical, if you want speed, and several things can change it - fuel type, comp. ratio, ignition advance and jetting. You need to control them all.
 
worntorn said:
I tested some original Norton black caps on Dyno hill. They sapped the power bigtime.

Glen
Click to expand...
From what I can gather a MK3 fitted with separate down pipes and pea shooters would be the best combination
I'm pretty sure the air filter box is large enough to not cause any restriction?
 
Mart UK said:
Why do you think the balance pipe in headers affects performance?
Click to expand...
Before my Seeley Commando had a Norton motor, it was a Seeley Laverda 750, and I had raced my Triton 500 against it in a club event. I noticed that it had a 2 into 1 exhaust systemwhich had a tail pipe which was too small. But because I was racing against it, It did not mention that to the guy who owned it. I blew that bike to the weeds down the back straight at Winton, but I noticed how it handled. I followed it around for about 2 years until I was eventuaslly able to buy the rolling chassis, but I could not get the motor. If you have a look at the photos of the 750 SFCs, the factory used to race, you will see the cross in the exhaust system which is under the motor. The 750SFC Laverda has a 180 degree firing motor - NOT 360, so the tail pipe does not resonate at twice the frequency of a header pipe. Each header pipe is able to exhaust into either muffler. So the back pressure is less.
I think one of Paul Dunstall's exhaust systems also used to do that. The 2 into 1 exhaust system on my bike is much too loud, but it works. And it only has one muffler.
 
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baz said:
From what I can gather a MK3 fitted with separate down pipes and pea shooters would be the best combination
I'm pretty sure the air filter box is large enough to not cause any restriction?
Click to expand...
That was the best exhaust combo out of 8 configurations I tried.

Glen
 
Mart UK said:
Why do you think the balance pipe in headers affects performance?
Click to expand...
I'm not sure.
The balance pipe probably does help a little when restrictive silencers are used.

My imagination going here-

Norton tester after riding a new M1a fitted with the new quiet Black Cap silencers
" Oh my God, we can't send these things out like this, they are completely gutless"

Norton management.
" We"ll stick a pipe across the headers. It will only cost a pound per bike and it will be good enough. Carry on!"
 
EstuaryBoy said:
Mr Hyde?? Doesn't he play the Trumpet??

At the risk of thread derailment (so what's new?), for me, it's not strictly about the numbers... 'adequate' is enough :)
But, and I'm sure many 'petrol heads' will get this, did you ever see a brochure/photo etc of a machine and think: 'YES!!'
I've got the NVT Mk3 brochure and that red Mk3 Roadster hit the spot here, as did a Classic Berk photo of a G85CS many moons ago.
For me, black caps are part and parcel of that bike's style, as peashooters are to earlier bikes. I know people put rayguns on T160s but to me that's an optical mismatch as well....

'Nuff said, so I will now ride off into the sunset....... slowly and quietly :)
Click to expand...
I framed my Mk3 brochure and is still hanging on my shed wall but I ended up buying the last old stock 74 model, I also framed my 81 Triumph brochure beside it on the shed wall.
Commando HP and Torque
Commando HP and Torque
 
Fast Eddie said:
There are straight through (perforated absorption tube) one’s available, the ones I’ve heard sound great, throaty without being harsh.
Click to expand...
Those are the ones. The original pair I had RGM make for me in the early nineties were fitted with pea shooter shark fin tubes. Quiet while cruising real throaty when opened up. Had to change them last year as baffle tubes broke. The replacements with the perforated baffle tubes sound even better especially on over run and feel like they've released a bit more power. Probably in my head.
 
I'm curious to know why all of these dyno numbers cannot be calibrated to show exact HP. My experience is somewhat limited but, in our shop, we built a boat with a Cummins 6-cylinder 610 HP engine driving an UltraJet jet drive rated for the same amount of power. The UltraJet engineers got on the phone with the Cummins people and sent us a prop which would hold our engine to 50 rpm below the governed rpm of 2300. I looked up all the Horsepower specs online and the curve is an engineering data curve which is able to be used to set the pitch of a prop to where it uses 100% of the available Horsepower at exactly 2250 rpm. These engineers aren't messing around or advertising to make sales. The data is absolute and can be used on the other side of the world to design stuff that matches and works as planned.
 
motorson said:
I'm curious to know why all of these dyno numbers cannot be calibrated to show exact HP. My experience is somewhat limited but, in our shop, we built a boat with a Cummins 6-cylinder 610 HP engine driving an UltraJet jet drive rated for the same amount of power. The UltraJet engineers got on the phone with the Cummins people and sent us a prop which would hold our engine to 50 rpm below the governed rpm of 2300. I looked up all the Horsepower specs online and the curve is an engineering data curve which is able to be used to set the pitch of a prop to where it uses 100% of the available Horsepower at exactly 2250 rpm. These engineers aren't messing around or advertising to make sales. The data is absolute and can be used on the other side of the world to design stuff that matches and works as planned.
Click to expand...
If only all dynos were calibrated the same as your Cummings engine ones
Sadly they are not
 
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