Available engine performance

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  1. As @SteveA says, timing and carbs. Did I say CARBS? New Premiers were great for me, and much easier to keep a tune than my old ones.
  2. Suspension. A Commando is a handling machine.
    1. Good tires
    2. good shocks for the rear. IKON are good mid range shocks that are an upgrade
    3. Lansdowne dampers for the front with new bushings and seals
    4. New vernier isolasitcs
  3. Sounds like you should keep the stock cam. But, you should look at it to inspect the lobes and the corresponding lifters for wear. It is amazing how well a shagged out cam on a commando can still work. And how much better it does with a good cam.
  4. If you do pull apart the motor, get the crank dynamically balanced. You will never regret it.
  5. If you do pull apart the motor, do a stage 1 build. I dont regret my 1+ build. So much fun and the motor spins up so fast it is scary even at stock displacement. But at -this point you are probably past bang-for-the-buck costs and into banged-for-the-bucks costs. But, you will have a smile.
 
gortnipper said:
  1. If you do pull apart the motor, get the crank dynamically balanced. You will never regret it.
  2. ....It is amazing how well a shagged out cam on a commando can still work......
Click to expand...
Dynamic balancing has a good rep, with a four cylinder crank I would want to do that, but don't knock static balancing as performed by the majority of twin cylinder tuners since Owen Greenwood started doing it in the '60s, right through to Steve Maney and many others. Owen did one in late '75 for me and Steve in about 2013, both excellent.

Yes, it is definitely possible to drag a cam out of a Norton and wonder why it was running at all!
 
+1 Steve.

I had my 850 crank dynamically balanced, unfortunately I did other things at the same time so it’s impossible to pin point what did what, but the end result was a transformation in smoothness.

However, when I built the 920 I discussed options with Steve Maney, I took his advice and he balanced it statically. And from my perspective it is every bit as good as the dynamic balancing.

So my conclusion is that good quality balancing by a knowledgeable person and correctly chosen balance factor are key, NOT dynamic vs static balancing.
 
The dynamic balance job locates and removes the rocking couple, if there is any. If there is no rocking couple or only a very tiny amount of it, then the static balance will be just as good as the dynamic.
The problem is, you don't know whether there is a rocking couple to eliminate without doing the dynamic balance.
So you need to get lucky with a static balance.
With the dynamic balance, luck is not required, its just Science.

Glen
 
Since the standard Commando crank balance factor statistics are known, and since many have undertaken similar refinements to very good effect, I don't think there's any need to wander too far afield for what the OP is looking for.
 
Airflow makes a vast difference, and there are people on here that achieve that with Norton heads. Does anyone have dyno comparisons for bikes modified this way? This is an old graph from 69 or 70 with rwhp of the superbikes of the day.

Available engine performance


The Triumph is the exact same spec as the Rocket 3 but obviously working well. It's interesting as these are stock bikes and Honda were claiming the highest by around 7hp and both the R3 and Trident are above what their makers claimed if you convert rear wheel to engine hp. Which is no way to sell motorbikes. Generally they claimed the best they got from an engine. This shows how test bikes compared.
 
Now that is an interesting graph. And a few surprises!
I expected a bit more from the Norton.
The Trident is impressive and demonstrates that beautiful spread of power they were known for
It certainly throws into question Honda’s figures.
The poor old Sportster is a tired old puffer.
I thought the Mach III might have peaked with a bit more power. From memory it certainly seemed that way when they were ‘on the pipe’
I can’t comment on the Royal Enfield or the American Eagle as they were never on my horizon.
thanks Al
 
That's pretty much the bunch that the Norton Commando cleaned up on in 1970, with a couple of non threatening low performers added. The original Superbike shootout.

Glen
 
Alan L said:
I expected a bit more from the Norton.
The Trident is impressive and demonstrates that beautiful spread of power they were known for
thanks Al
Click to expand...
The Norton is about 5hp ahead of the Triumph up to 5500rpm - which means more grunt for street useability
Actually 8hp at 3000rpm - 50% more than the Trident.
I wouldn't change from a Commando based on those figures!
 
Alan L said:
Now that is an interesting graph. And a few surprises!
I expected a bit more from the Norton.
The Trident is impressive and demonstrates that beautiful spread of power they were known for
It certainly throws into question Honda’s figures.
The poor old Sportster is a tired old puffer.
I thought the Mach III might have peaked with a bit more power. From memory it certainly seemed that way when they were ‘on the pipe’
I can’t comment on the Royal Enfield or the American Eagle as they were never on my horizon.
thanks Al
Click to expand...
The Norton makes about 1/3 more power than the Trident at 4000 rpm. It continues to make more power all the way to 6000 rpm. All that space between the lines is fun space, if you like torque ( who doesn't?)
For a roadbike, the Norton graph is head and shoulders above the Trident, no need to get in the power band, it's always in it.
The Trident has to be taken to the very top end to do well. But even then it couldn't quite keep up on the dragstrip on test. This was due to the extra weight of the Trident, about sixty pounds iirc.

Glen
 
Alan L said:
I thought the Mach III might have peaked with a bit more power. From memory it certainly seemed that way when they were ‘on the pipe’
Click to expand...

The legend Tony Nicosia in 1969. (Only 500cc)

"The H1 model run lasted eight years, from the first drum-brake 1969–71 H1 and H1A versions through the disc-brake KH500 swan song in 1976. Finally, the triple became a casualty of emissions laws and was replaced by the four-stroke KZ650 model. But what a run it was. Among its high points were those blistering early runs that Nicosia made at a special press demonstration at Lions Drag Strip in Southern California. Here personnel uncrated a brand-new H1 and put Nicosia aboard, where he soon scorched to the world’s first sub 13-second 1/4-mile run on a production bike. Although brand-new, the H1’s legend was already secure. "

The 1972 750 H2 was little different.

"As the first factory point man, Tony Nicosia was probably used in more Kawasaki ads than Terry Vance was used in Suzuki ads in later years. Tony’s claim to fame was undoubtedly the H1 500cc Mach III. The first round of ads taunted Tony’s accomplishments of setting drag racing records from California to Maine, and records at Bonneville. But they didn’t stop there. In 1972 when the 750cc Mach IV was introduced it was another Kawasaki ad that announced Tony’s breaking into the 11-second zone by setting a new AHRA record of 11.95 seconds at Fremont."

Of course there is more to it than getting to the next set of stop lights first in the real world but the 1970's was the beginning of a new era for big bore motorcycles.
I see little point in trying to make a Commando what it is not or change it so much it is no longer what it was.
Its a free world of course.
 
The Commando worked really well for getting to the next set of lights first in 1970.
Tony Nicosia prepared, Cook Neilsen aboard-
Kawasaki Mach 111 - 12.81 1/4 mile best run.
Norton Commando 750- 12.69 best run.

Glen
 
mark parker said:
Airflow makes a vast difference, and there are people on here that achieve that with Norton heads. Does anyone have dyno comparisons for bikes modified this way? This is an old graph from 69 or 70 with rwhp of the superbikes of the day.

Available engine performance


The Triumph is the exact same spec as the Rocket 3 but obviously working well. It's interesting as these are stock bikes and Honda were claiming the highest by around 7hp and both the R3 and Trident are above what their makers claimed if you convert rear wheel to engine hp. Which is no way to sell motorbikes. Generally they claimed the best they got from an engine. This shows how test bikes compared.
Click to expand...
There is a lot of A-B flow testing of various heads here, including mine. I think there is even some dyno info buried I here too.

Settle in with a cuppa/pint/high ball...

Edit: forgot the link. I guess that's what happens whwn you mix Cabernet+Codeine.

www.accessnorton.com

Head flow testing.

I would like to build up a database of flowtests on modified Norton heads. The tests would be done on one intake port and be from 0 to .450 lift and would include a single velocity measurement measured central in the port 3/4 inch in front of the guide. If anyone has a modified head setting...
www.accessnorton.com www.accessnorton.com
 
Last edited:
The Kawasaki was light, as was the Commando.

In 1970 BSA were testing what would be the works 750 3 I expect against the power graph of an A65 twin with A10 crank and almost matching it. The twin had 78hp @ 7,000 at the crank. They were revving the 3 to 9,500 and still shy. And even a hot 650 A65 was beating it to 5,500rpm. The biking world would have been different if only the 3 cylinders were based on the A65. Thunderbolts have 27mm ports like the triple except they flow 108cfm each. If they used the Spitfire cam, same bore, short stroke for a 750cc, pushrods inside, with the oil, the motorcycling world would have been a different place. On the mildest hp calculator that flow would enable 77hp.

With A65 stroke and '71 porting for a 981 triple 87hp and massive torque would have decimated the Z1 with technology they had, and those heads can be made to flow enough for that to be around 120hp in a race motor with fierce mid range. Yet they chose a 500 Triumph base with ports crowded with head studs, as if BSAs development didn't exist. And no less than 4 external pushrod tubes and separate rocker boxes to leak oil which were so unnecessary, as was all the complex crank cases with the expense and time intensive assembly.

And the head of the BSA/Triumph company was thinking they needed OHC motors to catch the modern Japanese advances.
 
Alan L , if you are not to keen to pull the motor apart, invest in a good ignition system, check your mechanical and ignition timing and a new set of Amal Premiers ( colour or Dyno tuned) or flat slide after market carbs will work wonders initially, as the protractor in the primary case can be out a few degrees as found by most of us and old Amals are not the best .
Taking into account your motor is in very good condition and you want to keep the price down, and are ok to take the head off (please tell the forum what model it is ie RH10) get a good head and Vv job as all power and torque is in the head. Sure bigger cams, bigger CC's and bigger compression will help (see expensive) but a very good clean up in the head will work wonders, especially in the intake tract and even with the stock cam these motors pull very strong.
Regards Mike
 
The main thing to to is eradicate anything impedeing performance .Thus ensure all the chain wheel alignment is good .
Ensureing the gearbox is top line and secure . If you cant handle the basic gearbox , steer clear of interfearing with the engine etc .

I regard the intakes manifolds as the biggest ' baulk ' to free breathing / running .
You cant regard anything with that wall length differance , top to bottom , as other than ' kinked ' . ensureing a degree of tumbling / stalling , at times .
A free curve / radius , through from the head to near level - with the carbs up against the frame gusset , gets a far more uninterupted tract .

The 72 JPS F-750 ran semi downdraft GPs at times . good for 155 mph . There was a 5600 or 5800 ' continuous ' rateing , in the Poore Era .
Tecnically the oil capacity is sup par . 3/4 Imp. Gallon with 1/4 breather space . I.E. ONE GALLON TANK . but use say your Std. amount for short trips ,
Full for touring / Summer use . And Racing .

The Oil Tube post 70 Triumphs , were a bit the same . a oil cooler adds capacity . But theres a ' ratcheting ' heating / cooling oil - continuously , thats bad for it .
So a thermo thingo helps .

18 in rear wheel will get better rubber . T.C. was a 16 in fan , for 5.00 16 tyres . But some might say he was heavy on the throttle .

So its mainly fettling it to get it all functioning top line . Like a better maintained Top Line fighter aircraft . An hours polishing should be worth a few m.p.h. ;)
 
gortnipper said:
There is a lot of A-B flow testing of various heads here, including mine. I think there is even some dyno info buried I here too.

Settle in with a cuppa/pint/high ball...

Edit: forgot the link. I guess that's what happens whwn you mix Cabernet+Codeine.

www.accessnorton.com

Head flow testing.

I would like to build up a database of flowtests on modified Norton heads. The tests would be done on one intake port and be from 0 to .450 lift and would include a single velocity measurement measured central in the port 3/4 inch in front of the guide. If anyone has a modified head setting...
www.accessnorton.com www.accessnorton.com
Click to expand...
My heads in that thread too. Showing before and after flow and velocity numbers plus corresponding before and after Dyno numbers. Bottom line was a 9bhp increase.
 
mark parker said:
The Kawasaki was light, as was the Commando.

In 1970 BSA were testing what would be the works 750 3 I expect against the power graph of an A65 twin with A10 crank and almost matching it. The twin had 78hp @ 7,000 at the crank. They were revving the 3 to 9,500 and still shy. And even a hot 650 A65 was beating it to 5,500rpm. The biking world would have been different if only the 3 cylinders were based on the A65. Thunderbolts have 27mm ports like the triple except they flow 108cfm each. If they used the Spitfire cam, same bore, short stroke for a 750cc, pushrods inside, with the oil, the motorcycling world would have been a different place. On the mildest hp calculator that flow would enable 77hp.

With A65 stroke and '71 porting for a 981 triple 87hp and massive torque would have decimated the Z1 with technology they had, and those heads can be made to flow enough for that to be around 120hp in a race motor with fierce mid range. Yet they chose a 500 Triumph base with ports crowded with head studs, as if BSAs development didn't exist. And no less than 4 external pushrod tubes and separate rocker boxes to leak oil which were so unnecessary, as was all the complex crank cases with the expense and time intensive assembly.

And the head of the BSA/Triumph company was thinking they needed OHC motors to catch the modern Japanese advances.
Click to expand...
and they made a SOHC prototype and it didn’t do much different, apparently due to inherent inlet restrictions.
 
mark parker said:
Airflow makes a vast difference, and there are people on here that achieve that with Norton heads. Does anyone have dyno comparisons for bikes modified this way? This is an old graph from 69 or 70 with rwhp of the superbikes of the day.

The Triumph is the exact same spec as the Rocket 3 but obviously working well. It's interesting as these are stock bikes and Honda were claiming the highest by around 7hp and both the R3 and Trident are above what their makers claimed if you convert rear wheel to engine hp. Which is no way to sell motorbikes. Generally they claimed the best they got from an engine. This shows how test bikes compared.
Click to expand...
Which magazine did this come from Mark? The 1970 Cycle shootout test perhaps?
 
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