750/850 weight comparison

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Just weighed the Norton 750 P11 and it is 374lbs with 1/2 tank of gas. Totally off topic, but it would have an unfair advantage with me on it. lol

Had to take the seat off and lay it sideways on the frame to be able to get the bike off the ground using even length soft ties and not destroy the seat. good thing I have an old motor hoist laying around. I've always wondered what it weighed. I knew it was lighter than a chubby stock Commando.

750/850 weight comparison


750/850 weight comparison


750/850 weight comparison
 
Just weighed the Norton 750 P11 and it is 374lbs with 1/2 tank of gas. Totally off topic, but it would have an unfair advantage with me on it. lol

Had to take the seat off and lay it sideways on the frame to be able to get the bike off the ground using even length soft ties and not destroy the seat. good thing I have an old motor hoist laying around. I've always wondered what it weighed. I knew it was lighter than a chubby stock Commando.

750/850 weight comparison


750/850 weight comparison


750/850 weight comparison
I once weighed a homemade alu boat trailer with a lightweight (450 lbs) sailing catamaran on it using five cheap bathroom scales. Each scale went to 300 lbs. Put a board across two scales, with one wheel of trailer on the board. Same on other side wheel. One more scale for front tongue wheel. Adding up all the scale displays gave total. Did this to determine overall weight for selecting correct capacity suspension axle and placement of axle to get needed 5% tongue weight for best towing weight distribution.
A similar method could be used for weighing a bike if no crane and high capacity scale was handy.
 
I once weighed a homemade alu boat trailer with a lightweight (450 lbs) sailing catamaran on it using five cheap bathroom scales. Each scale went to 300 lbs. Put a board across two scales, with one wheel of trailer on the board. Same on other side wheel. One more scale for front tongue wheel. Adding up all the scale displays gave total. Did this to determine overall weight for selecting correct capacity suspension axle and placement of axle to get needed 5% tongue weight for best towing weight distribution.
A similar method could be used for weighing a bike if no crane and high capacity scale was handy.
I've been advised of that same method more or less by gortnipper.

As simple as that method might sound to a lot of people that still have good functioning brain cells, it was easier for me to buy the cheap scale and soft ties and use the motor hoist for a bulk weight number.

I'm not so sure on the accuracy of that $32 scale, but the number was repeatable 4 times dropping the bike back to the ground resetting the scale and lifting again from 0.

Did this for two reasons: Curiously and to get the right spring rate for the forks. I was way off on the soft side on the initial spring rate guesstimate. I got much closer on the second guess I'm using now. I will be playing a little with fork fluid levels in the future. Anyway, I'm getting off topic yet again.
 
I've weighed my Commando using a bathroom scale under one wheel at a time (bike level) and adding the weights and also by using an engine hoist and a crane scale...both came up with 460 lbs. give or take only a pound or two. This weight is for a '73 850 Interstate with the tank about half full.
 
Hi all,
After reading this thread I am increasingly feeling rather foolish and dudded.
For years as a young bloke I hankered after a Commando but fell for the very prevalent belief that a MkIII was over weight, poorer performing and less reliable than the svelte and nimble MkII. I really thought that the earlier bike was the better bike. It has dawned on me that I was just a victim of the anti-British propaganda that was very common in the late seventies and beyond.
Particularly after reading this topic I realise now that I was duped. The MkIII was the arguably best of the bunch, as it should be being the last made and the beneficiary of all the previous experience from earlier bikes. Of course it’s a bit heavier, it has a starter strapped onto it. Yes, the black cap exhausts were restrictive but a change to other pipes would have been an obvious improvement and yes, I’m sure many were delivered with manufacturing faults as a result of the antiquated production process and perhaps the fact the company was in dire straights. These issues would have been rectified by the time I was in a position to straddle one of my own.
Anyway, I have no complaints with my late MkII roadster which just seems to get better and better the longer I own it and the more I ride it but I recognise how easier it is to be influenced by false news, back then and now today.
As a last thought, it’s probably important to realise that the anecdotal performance of a bike, as described by ordinary owners, not by professional riders and testers, is greatly influenced by how noisy the exhaust is. A rorty snarling exhaust gives the impression of more performance whereas the constipated hissy black cap mufflers gave the impression of a greater loss of performance than they actually created.
Every time I see a MkIII now I kind of wish I had bought one.
regards
alan
 
'constipated hissy black cap mufflers' !!!

I was in the outside lane of the A131 a few weeks back, daydreaming as usual, then realised my exit was fast approaching the 'too late now' stage. Full throttle overtaking followed by some disgustingly late braking saw me just wing it.
And the soundtrack???
Definitely more Wagner than Debussy.... (But only when they're angry :-) )
 
'constipated hissy black cap mufflers' !!!

I was in the outside lane of the A131 a few weeks back, daydreaming as usual, then realised my exit was fast approaching the 'too late now' stage. Full throttle overtaking followed by some disgustingly late braking saw me just wing it.
And the soundtrack???
Definitely more Wagner than Debussy.... (But only when they're angry :) )
Flight of the Valkyries no doubt! (or perhaps De Vliegende Hollander, if you were lost and cursed to forever wander the motorways looking for your exit😉)
Alan
 
Hi all,
After reading this thread I am increasingly feeling rather foolish and dudded.
For years as a young bloke I hankered after a Commando but fell for the very prevalent belief that a MkIII was over weight, poorer performing and less reliable than the svelte and nimble MkII. I really thought that the earlier bike was the better bike. It has dawned on me that I was just a victim of the anti-British propaganda that was very common in the late seventies and beyond.
Particularly after reading this topic I realise now that I was duped. The MkIII was the arguably best of the bunch, as it should be being the last made and the beneficiary of all the previous experience from earlier bikes. Of course it’s a bit heavier, it has a starter strapped onto it. Yes, the black cap exhausts were restrictive but a change to other pipes would have been an obvious improvement and yes, I’m sure many were delivered with manufacturing faults as a result of the antiquated production process and perhaps the fact the company was in dire straights. These issues would have been rectified by the time I was in a position to straddle one of my own.
Anyway, I have no complaints with my late MkII roadster which just seems to get better and better the longer I own it and the more I ride it but I recognise how easier it is to be influenced by false news, back then and now today.
As a last thought, it’s probably important to realise that the anecdotal performance of a bike, as described by ordinary owners, not by professional riders and testers, is greatly influenced by how noisy the exhaust is. A rorty snarling exhaust gives the impression of more performance whereas the constipated hissy black cap mufflers gave the impression of a greater loss of performance than they actually created.
Every time I see a MkIII now I kind of wish I had bought one.
regards
alan
In the second video I made sure that the tuned 750 was already accelerating under full throttle before rolling the MK3 on.
Its very hard to gain enough speed to prevent the first bike from pulling away.
This is because of simple Physics.
If two identical vehicles with identical acceleration curves race in a time delay manner, we'll say 2 seconds between them at start, there will still be 2 seconds between them at the finish.
2 seconds at the start is about 60 feet but at the finish (110 mph) it is about 300 feet.
So if you raced yourself and let yourself go first, the early version of you continuously pulls away from the later version of yourself. The bike that leaves first is always further along the velocity curve, always at a higher velocity due to the time difference, so it keeps pulling away .
The MK3 fell behind at the start due to the time delay, then held the other bike even until about 80 mph. The only way to do that is to accelerate harder than the bike that left first.

Glen
 
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Hi all,
After reading this thread I am increasingly feeling rather foolish and dudded.
For years as a young bloke I hankered after a Commando but fell for the very prevalent belief that a MkIII was over weight, poorer performing and less reliable than the svelte and nimble MkII. I really thought that the earlier bike was the better bike. It has dawned on me that I was just a victim of the anti-British propaganda that was very common in the late seventies and beyond.
```.
Every time I see a MkIII now I kind of wish I had bought one.
regards
alan
The motorcycling press around that time gave the impression that the holy grail was a BMW and anything else was less than. Nortons and Triumphs were rubbish.
Until I took a ride on one. It vibrated in a different manner and was just as quirky in its own way as my Commando and not as fast!
 
I have an 850 with a standard engine, but with a single 38mm carb. 22 tooth sprocket. I do have 1 1/2" exhausts with straight through pea shooters. Not really the set up to go fast. My friend has a 750 with the original dual carbs, a PW3 cam and also Dunstall 2:1:2 exhaust (good for 15 HP apparently) I am pretty sure my bike is faster than his. I notice it on big long hills. I have always suspected that his cam timing is not right. I have told him a way we can check it just by looking in the exhaust ports, but he says taking the exhaust off is to much work.
 
I tried the Dunstall 2-1-2 on Dyno Hill. The original ad claimed the exhaust alone would knock 1.15 seconds off 1/4 mile time, get it down to mid 11 second range normally inhabited by 100 + HP bikes.
Instead the bike went slower than stock, even after multiple jetting changes.

I also tried 1 1/2" exhausts on open Pea shooters. They slowed the bike a bit as well. Balanced stock 1 3/8" also not great.

The very best result was with separate 1 3/8" on open Pea shooters, just as an early 850 or most 750s would have had as original equipment.
I forgot to plug the balance pipes for the runs above. I might do that if we do another run at some point. It makes a small difference in the right direction.

Glen
 
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I tried the Dunstall 2-1-2 on Dyno Hill. The original ad claimed the exhaust alone would knock 1.15 seconds off 1/4 mile time, get it down to mid 11 second range normally inhabited by 100 + HP bikes.
Instead the bike went slower than stock, even after multiple jetting changes.

I also tried 1 1/2" exhausts on open Pea shooters. They slowed the bike a bit as well. Balanced stock 1 3/8" also not great.

The very best result was with separate 1 3/8" on open Pea shooters, just as an early 850 or most 750s would have had as original equipment.
I forgot to plug the balance pipes for the runs above. I might do that if we do another run at some point. It makes a small difference in the right direction.

Glen
Hi Glen,
Very interesting!
It certainly would seem to be false advertising to suggest a set of pipes could knock 1.5 seconds of the quarter mile time. A mid eleven second time from an otherwise stock bike would have been the stuff of legends. Smarter readers than me could calculate the required horsepower increase to achieve this but I suspect nothing short of a supercharger, as an individual item, could provide that sort of power increase.
I don’t know how many commandos ever achieved 11.5 seconds under verifiable conditions but I’d bet they’d had a fortune spent on them and a rather limited life.
But I was most interested in the fact you mentioned blocking off the balance pipe. How did you do this? Do you have any photos? Some years ago I replaced my original Triumph T140V pipes with non balanced ones. I am absolutely sure it substantially sharpened up the bikes performance as well as giving it a much crisper (and louder) exhaust note. I haven’t noticed any loss of power in the lower rev range that is often attributed to not having a balance pipe.
I would be keen to try the same with my very stock MkII but don’t really want to replace an otherwise perfect set of header pipes.
Alan
 
I made up some temporary plugs in aluminium. These were tapped in after the cross- pipe was removed.
This gave a measureable increase in speed at top, 113 kmh instead of 110kmh.
There would still be turbulence at the cross pipe exit locations. A proper set of separate pipes should be even better, but you never know, it might not.
I have thought of welding the pipes up permanently with stainless to replicate regular separate pipes.
A normal person would just purchase new separate headers.

Glen
 
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