Standing quarter times.

Dyno figures for old Brit bikes are pretty meaningless unless the bike is being used for competition, as is talk of standing 1/4 mile times. High performance is not something anyone owning a bike fitted with a motor based on a 1947 design is likely to be looking for in any case, and if it is then maybe a more modern machine would be better suited?

[quote as is talk of standing 1/4 mile times. High performance is not something anyone owning a bike fitted with a motor based on a 1947 design is likely to be looking for in any case, and if it is then maybe a more modern machine would be better suited?][/quote]

Just curious to know what others have done.

Sure, if I wanted to do an 8.5 I'd get a hayabusa.

Regardless of the age or origin of our bikes, it's nice to get the best from them.

Commandos are not some old geriatric priceless museum pieces, they are a still reasonably capable road bike, with sports performance if given the berries. And we are discussing what they were capable of in their day - which should still be repeatable today. Although obviously thrashing them mercilessly, they are not going to last like modern machinery.

Can't readily find them, but a few dyno tests back in their day had the road 850's producing ~42-45 rear wheel horsepower, the Combat 750 had a few hp more, at ~1000 rpm more. And the Norton Villiers JPN Race bikes were quoted as ~74 bhp on the dyno (thats engine hp, not rear wheel).

Be interesting to hear what these 920cc or bigger engines are outputting. ?

Combat Col said:

[quote as is talk of standing 1/4 mile times. High performance is not something anyone owning a bike fitted with a motor based on a 1947 design is likely to be looking for in any case, and if it is then maybe a more modern machine would be better suited?]

Click to expand...

Just curious to know what others have done.

Sure, if I wanted to do an 8.5 I'd get a hayabusa.

Regardless of the age or origin of our bikes, it's nice to get the best from them.[/quote]

I would think "the best" is relablity and nice quite running,risking a blown engine at worst,or valve bounce and a bent valve is the last thing busy guys need these days :!:
Sorry but been there, blow up my suzui 350 street jousting. crank then in 72 was a whooping £60..three weeks pay :!: i think i missed a mortgage payment that month. she was treated it like a baby after that!
Expensive lessons teach us the right way to look after things...anyway i really liked that bike. and the wife missed our fish and chip friday treat!

Carbonfibre wrote that. I think I missed the quote marks.
They are awesome machines and don't need to be nursed. If we didn't like working on them we wouldn't own them.
Maybe some people are more suited to maintenance free Jappers. And that's fine too !

At the 92 INOA rally the dyno we had all commers run their commando's. 38-43 rear wheel HP was the trend. My combat made 47 RWHP , and was remarkedby Leo Geoff as the highest HP non profesionally tune combathe had seen....49 being the best ever for a stock commando( albeit a combat). A few "race"/hot rod commandos yeilded almost 60 RWHP.
same dyno same weekend, so the relationship seemed valid for me.....but I was actually more interested in the torque curves.
I saw one torque curve of a hotrod and noted that his torque was so much lower at low RPM's that in real world he would need the extra high end power to play catch-up... :mrgreen:

I've kept mental track of various dyno reports since '99, with enough of them both crank and rwph to tell ya that Commando's lose about 9% in drivetrain. Steve Maney wrote me 5 year ago his 920's crank hp @ 7200 = 100.4 hp. Nitro fueled Dragonslayer made 150 each its claimed.

If DynoDave gets caught up to post on his site I sent him some interesting period articles/tests on Drouin 750's.
I've played with various engine calculators for Ms Peel down to valve ports and mach numbers with cam lifts and boost on top and ignition curve per octane ratting. Could get over 120 rwhp and over 100 lb ft at crank - by mid range rpm. With Hole Shot device and ass suck down Ms Peel may break 10 sec 1/4's. As powerful as that sounds its just thin icing on cake of rear rump rod + helpers in road work so only hope the straights can provide similar G's I get when leaned on mere Combat power against elite sports bikes - the dangerous corner cripples. She has 130 tire fitted now to test its bite upright or leaned

Like it or not a hod rod Brit twin producing anywhere near the same power as a Jap 600 four, isnt likely to be producing that amount of power for very long. Why not just enjoy the bikes as they are and carry out alterations to increase reliability, and improve running by replacing very poor OE ignition and carburetion?

Why and Why not...when I was young, I had a BTB (built to blow) Triumph with about 15:1 compression or so. One day on Alkeehawl and about 10% nitro I dumped the clutch and KA-BOOM! Fortunately the pegs were on the rear axle because when I looked down the head was dangling from the torque stay and there was this big space between the head and these two little stubs on the crankshaft that use to be connecting rods. Then, I wanted to know why that happen. Now, I wanna know why I spent all that money!

I was talking with a friend about eating a cow's tongue sandwich and he said "Yuck, I'm not eating anything that came out of an animals mouth!" So, I ask him, "What's your favorite sandwich?" He replied "Egg salad".

It's really a matter of perspective isn't it? :lol:

Just my penny's worth.

Mike

Combat Col said:

Went to test and tune night at the local strip (Willowbank) for a bit of fun on Sat night.
Managed a best run of 14.28 @ 90.53 mph. I'm no professional drag racer, have a non functioning revometer and am about 93 kilos.
Pretty pleased with the result, all things considered.
I heard somewhere that a stock Combat ran 12.4 many years ago, no doubt with a 60kg pro piloting. The question is, "Who's done what ?"
Curious to know any real figures, and what is a realistic expectation.
I'd like to think that if I lost 10 kgs and had a bit more practice, we could be in for mid 13's ?? Any thoughts ??

Click to expand...

Best not to make any claims on this forum without a certified strip ticket, but your time and speed sound low for a 750 combat. Do you have 21T or 19T gearbox sprocket? My '73 strip run at Ontario, Ca was low 12s over 100mph on a very low mileage combat, freshly tuned and running period +100 octane leaded gas. Bike was as shipped from new...exept for '73 auto advance unit for the points. I weighted about 160lbs then.

So what is it you like to remember most in your short lives, how careful tame you were w/o much to stand out or. ....

Its so silly to me to hear all the caution notes on how hard it is on our jump rope push rod air cooled elastic engines, when the facts of the matter is any cycle over 250 is pure luxury item for its consumables, so if you got one bigger than that you are self contradicting any logic offered to economy or rational reasons not to press it till something blows up or just short of it, till renewed to do it some more. I love the pull of my factory Combat but accept it for what it is a 40 yr old clunker sabotaged by design over sights, bean counters and feed up factory workers, no need to alter for safe thrills but not a record breaker any more. Wonder what went through TC's head putting all that expense out then dumping it hard as he could... tell him how immature and on his permanent record it will stain : )

Two more things of note, one the Combat and Cdo's in general have the guts below the ton to take on about anything in real world public riding thrills, extra hp only come into play over torque as the air drag builds after 120 mph - so most road work Cdo can pull as hard as a modern entering of leaving turns, up to hp hard pull limit.

Other thing is you well tuned and geared Combat riders ain't fibbing to tell strangers its an under 13 sec 1/4 bike right out the Norton box.

I ran my '71 at a strip a bunch of years ago. I had one good run out of three. I think I managed low 14s. My other two runs, I'd rather not talk about!

A buddy of mine used to be a pretty serious hobby drag racer. There is definately some skill involved...

Bob

Its very scary to me to do standing start launches but most of a second is gotten doing that under full thrust. My factory Combat per-Peel got mid 11 sec and 87 mph
in 1/8 mile of avatar day tire fold crash. It takes hardened heart to your machine to max it out for what its worth. Then get more lesions in fine control with adrenaline spikes. No plans to wheelie a factory Cdo any more thankyou. Next hot rod will be wheelie proof unless intended. Wheelies above floating level are wasting energy forwards.

When ya get to some level of power to weight that throttle can set tire spin speed one to one with throttle action, it transforms the ride and the pilot antics.

Thank you all, I wasn't implying that we all should go out and Dyno our bikes. I was just wondering if anyone had, and
did the figures stack up. I don't care how many H.P. my bike has, but I would have thought back in the day when people
wrote things like.." Fastest production bike in the world " etc. That many in this Forum would have done just that.
Any way, calm down it doesn't matter. Just asking. That's all.
I have to say that a friend of mine in the seventies ran a Dyno Tune center here in Adelaide, for cars, and it is an easy way
to tune an engine. A few seconds at full throttle in top gear with a load on at 60, 80 and 100 mph ( if possible ).
No worse than passing a Bonneville with the wife on the back.
Well it sounds good anyway.
AC.

hobot said:

So what is it you like to remember most in your short lives, how careful tame you were w/o much to stand out or. ....

Its so silly to me to hear all the caution notes on how hard it is on our jump rope push rod air cooled elastic engines, when the facts of the matter is any cycle over 250 is pure luxury item for its consumables, so if you got one bigger than that you are self contradicting any logic offered to economy or rational reasons not to press it till something blows up or just short of it, till renewed to do it some more. I love the pull of my factory Combat but accept it for what it is a 40 yr old clunker sabotaged by design over sights, bean counters and feed up factory workers, no need to alter for safe thrills but not a record breaker any more. Wonder what went through TC's head putting all that expense out then dumping it hard as he could... tell him how immature and on his permanent record it will stain : )

Two more things of note, one the Combat and Cdo's in general have the guts below the ton to take on about anything in real world public riding thrills, extra hp only come into play over torque as the air drag builds after 120 mph - so most road work Cdo can pull as hard as a modern entering of leaving turns, up to hp hard pull limit.

Other thing is you well tuned and geared Combat riders ain't fibbing to tell strangers its an under 13 sec 1/4 bike right out the Norton box.

Click to expand...

I wonder have you ever ridden a good modern machine such as the S1000RR for instance? Not completely sure that an old Brit twin with maybe 65bhp is going pull quite as hard out of turns as the RR with 193bhp?

Carbonfibre said:

hobot said:

So what is it you like to remember most in your short lives, how careful tame you were w/o much to stand out or. ....

Its so silly to me to hear all the caution notes on how hard it is on our jump rope push rod air cooled elastic engines, when the facts of the matter is any cycle over 250 is pure luxury item for its consumables, so if you got one bigger than that you are self contradicting any logic offered to economy or rational reasons not to press it till something blows up or just short of it, till renewed to do it some more. I love the pull of my factory Combat but accept it for what it is a 40 yr old clunker sabotaged by design over sights, bean counters and feed up factory workers, no need to alter for safe thrills but not a record breaker any more. Wonder what went through TC's head putting all that expense out then dumping it hard as he could... tell him how immature and on his permanent record it will stain : )

Two more things of note, one the Combat and Cdo's in general have the guts below the ton to take on about anything in real world public riding thrills, extra hp only come into play over torque as the air drag builds after 120 mph - so most road work Cdo can pull as hard as a modern entering of leaving turns, up to hp hard pull limit.

Other thing is you well tuned and geared Combat riders ain't fibbing to tell strangers its an under 13 sec 1/4 bike right out the Norton box.

Click to expand...

I wonder have you ever ridden a good modern machine such as the S1000RR for instance? Not completely sure that an old Brit twin with maybe 65bhp is going pull quite as hard out of turns as the RR with 193bhp?

Click to expand...

I have riden Both, Ok it was a only a honda black bird 163 bhp and a old 750 commando...corner exit speed was slower on the honda...back wheel spinning and the whole bike sliding side-ways did't help much :!:

Sheeshe , any ' like new ' Commando ( bar a Mk3 ) should cut 12.5 or better .
The dog , O'hauled @ 7104 miles , (main bearings , NOT a Combat ) running 8.7:1 C.R.
2S cam ( 5 deg. early) , 32 Mk II amals and a 23 tooth sprocket was a pig to get out of
the Toll Gates in winter rain . Stall or dribble the clutch for 50 yds , applying a bit of
throttle had it wheelspinning past 100 yds out. Cold , wet , smooth bitumen .

Only good drag I had on it was Vs XS 1100 with 4-1 Ex. Got half a length on one start ,
he on the other . No diff whatsoever till 80 mph & RED Lights ! :lol: . XS11 is rated @ 11.5 sec Quater stock .
Commando had a std. ' S ' cam back in then . Easier of line , but not as much snot over 4.000 rpm .

Also ran valves @ .016 & BSA 36 Deg. Adv. but this was 1980 or so , while pump gas was still 98 .

' Testers ' in the states generally lit the rear tyre of the line . I dindnt try any of that millarky . :roll: :mrgreen:

The Pre Unit Bonnie , tweaked , when it was clapped out pulled a timed 14.5 Quater . would be near 2 sec less easy
as one or two dudes would testify . Probably better .

Guess its the hair trigger reactions , and all the hours spent keeping all the adjustments spot on , lever free play ,

positions , lube etc etc . An average overhaul was all to specs , so called ' blue printing .

It had to be a pretty lemonie or neglected abused machine to not better this , with a ' keen pilot ' .

ANY Bonnie or Commando , right shift , should pull 115 mph , BEFORE you start setting it up with ' improvements ' .

I wonder have you ever ridden a good modern machine such as the S1000RR for instance? Not completely sure that an old Brit twin with maybe 65bhp is going pull quite as hard out of turns as the RR with 193bhp?[/quote]


I have riden Both, Ok it was a only a honda black bird 163 bhp and a old 750 commando...corner exit speed was slower on the honda...back wheel spinning and the whole bike sliding side-ways did't help much :!:[/quote]

Sounds like you needed a lot longer on the Honda to get used to having some serious power?

Are we aware that a bike pulling mid eleven second quarter mile times would HAVE to be hitting its terminal speed around 110mph, OR SO? and NOT 87mph?

Let's get real, any twenty year old Japanese four 600cc will eat a Commando alive, both in top end and also in quarter mile time.

1up3down said:

Are we aware that a bike pulling mid eleven second quarter mile times would HAVE to be hitting its terminal speed around 110mph, OR SO? and NOT 87mph?

Let's get real, any twenty year old Japanese four 600cc will eat a Commando alive, both in top end and also in quarter mile time.

Click to expand...

Come on this is the net...........where old 1947 designed Brit twins can top 160mph, and out handle and out brake modern sports bikes..............lol

Seriously though for any bike to run mid eleven 1/4s its going to need substantially more power at the rear wheel, than even the doctored up 1970s Norton test machines, which often ran on methanol to allow ultra high compression ratios.