H.P mods ?

Status
Not open for further replies.
The best thing you can do to a 47 RWHP bike for power is to tune it well through it's mid range so you get out of it, all the HP it's got. If your speed modifications get you another 3-5 hp, that's great, but you're still on a ~50-ish HP parallel twin. At best, you are faster on your norton than your buddy is on his. Everyone with a 80+ HP bike blows your doors off in straight line acceleration.

with a commando, I'd work on handling, suspension, and brakes improvements, then make sure the ignition timing and carburation are perfect. Get good tires and you'll do surprisingly well in the twisties...

If you want power for speed runs on the salt at Bonnieville that sort of power modification is a whole 'nother animal....
 
@o0norton0o has it right, tires are important too!

@Knucles, when the time comes that you decide you are ready to START spending money on performance modifications, you need to consider your REGULAR riding style, and WHICH mods would best compliment THAT type of riding.

What I've done with all my bikes, going back to at least the last 100 of 170+ bikes I've owned, is to have a 3-column tab in each bike's spreadsheet. Those three sections are

"Priority" - WHAT THE BIKE NEEDS TO RUN RIGHT (and/or be street-legal);

"Non-Priority" - "Upgrade" stuff I'd like to do to the bike in the near future, typically involving parts I've got on the shelf that have been sitting a while;

"Future" - Major, expensive, and/or custom items, or simply one line saying "refurbish" or "total restoration". The "Future" column is always dependent on major cash outlay, so rarely ever happens.

So, maybe lay out all the suggestions you get, and drop them into those 3 columns. Then, "follow the money", do what your budget allows.
 
Knucles said:
what can be done to increase h.p. In the 750 cc engines ?
what is the most h.p. You can get to with street fuel ?
i just have an interest in what can be done .
not that I want to do it on mine . I want to stay with reliability .
I can remember about 40 years ago a friend had a bunch of work done on his . He seemed to have a lot of problems and the bike was being fixed very often .
I don’t remember what he had done .
what mods can be done on a street bike and what hp increases do they give ?
Click to expand...
 
Thanks grandpaul . I will follow through what you posted .
my idea was not to add engine hop up items .
I feel with these bikes that proper set up and tune are all I was planning on . .
 
As pointed out, mods must be sorted to work together with the stock parts or other mods. Just changing to a "high performance" item and expecting it to increase power is expecting too much. I have seen "high performance" camshafts, exhausts and an almost endless number of "bigger carburetors" reduce performance over stock.

Ironically, in almost every case, the owner (who was often the installer) "could feel the added power." But 1/4 mile and/or dyno tests proved the opposite. ;)
 
grandpaul said:
@o0norton0o has it right, tires are important too!

@Knucles, when the time comes that you decide you are ready to START spending money on performance modifications, you need to consider your REGULAR riding style, and WHICH mods would best compliment THAT type of riding.

What I've done with all my bikes, going back to at least the last 100 of 170+ bikes I've owned, is to have a 3-column tab in each bike's spreadsheet. Those three sections are

"Priority" - WHAT THE BIKE NEEDS TO RUN RIGHT (and/or be street-legal);

"Non-Priority" - "Upgrade" stuff I'd like to do to the bike in the near future, typically involving parts I've got on the shelf that have been sitting a while;

"Future" - Major, expensive, and/or custom items, or simply one line saying "refurbish" or "total restoration". The "Future" column is always dependent on major cash outlay, so rarely ever happens.

So, maybe lay out all the suggestions you get, and drop them into those 3 columns. Then, "follow the money", do what your budget allows.
Click to expand...
With some training we may have made a systems engineer out of you! ;)
 
Well over 40 years ago a Mr John Hudson wrote a series of tuning notes.

Doing what he recommended will go a long way to building a reliable motor able to deliver the performance available from the basic configuration.

Somewhere, possibly Dyno Dave had them, there is a copy of these notes online.

That will go some way to answering your questions, but....you would still be best placed to commit something to a list of requirements....what you want to achieve....targeted at the riding experience, not the build or bragging experience.
 
SteveA said:
Well over 40 years ago a Mr John Hudson wrote a series of tuning notes.

Doing what he recommended will go a long way to building a reliable motor able to deliver the performance available from the basic configuration.

Somewhere, possibly Dyno Dave had them, there is a copy of these notes online.

That will go some way to answering your questions, but....you would still be best placed to commit something to a list of requirements....what you want to achieve....targeted at the riding experience, not the build or bragging experience.
Click to expand...
tuning notes?
I have only a paper copy of NOC Commando service notes-1979 John Hudson being co author. It has been reedited and added to a few times.
I also have the paper Dunstall booklet.
Jim Schmidt's tips
I also have the INOA tech digest ver1, ver2 and ver3-1999, which I was contributing editor but has some sections now a bit outdated.
My filing cabinet is overflowing with my 30 years of NHT research, a small amount went in the INOA TD ver3 , most did not. A very small amount is on my website.
The residue is in my brain and fading fast.

dynodave
 
dynodave said:
tuning notes?
I have only a paper copy of NOC Commando service notes-1979 John Hudson being co author. It has been reedited and added to a few times.
I also have the paper Dunstall booklet.
Jim Schmidt's tips
I also have the INOA tech digest ver1, ver2 and ver3-1999, which I was contributing editor but has some sections now a bit outdated.
My filing cabinet is overflowing with my 30 years of NHT research, a small amount went in the INOA TD ver3 , most did not. A very small amount is on my website.
The residue is in my brain and fading fast.

dynodave
Click to expand...
I have seen them somewhere. Your collection came to mind. My copy was typed out by my wife from a copy loaned to me and returned to our local Norton dealer in 1975!

John Hudson left them behind when touring dealerships through that period. They are based on a sensible approach to an engine rebuild, some would say blueprinting, with the intent of obtaining best performance and reliability from a broadly standard set up. It has some data on cam choice. Not much more. But oh so helpful to me, then a young aircraft technician with little engine build experience.
 
Last edited:
I am generally conservative with things mechanical. My general desired path is as you say to try and "blueprint" and fuss over the tolerances. When machinery seems stone age simple, the reliability is based on all the parts being better than just OK . Measuring and evaluating the actual build is alway the attempt I strive for. One unreliable part can bring down the whole machine. In my early college days a quality control class they discussed IIRC how Jap car tolerances were specified 10x more accurate than american car MFG. Two different concepts, design tolerance and manufacturing tolerance. NHT specified 50W oil and modern uses 5-30. Would you use 5-30 in your NHT? Especially with a worn out oil pump?:eek: So I designed and built an oil pump tester.....who else does that?
 
Last edited:
Loose motors are sometimes faster than tight ones, as long as the piston rings and valves seat properly. Fitting pistons at the correct tolerances is often not necessary, unless the piston slap is too great. Commando motors have very long stroke, so piston slap is not such a big problem.
 
Knucles said:
what can be done to increase h.p. In the 750 cc engines ?


... I want to stay with reliability .
.... seemed to have a lot of problems and the bike was being fixed very often ....
Click to expand...

If you want reliability along with performance then you have to reduce stresses on the motor by reducing the reciprocating weight (the shaking forces). The same forces cause wires to break and parts to fall off. They break cases, crankshafts and rods and are the reason Norton came up with the isolastic mounts.
 
acotrel said:
Loose motors are sometimes faster than tight ones, as long as the piston rings and valves seat properly. Fitting pistons at the correct tolerances is often not necessary, unless the piston slap is too great. Commando motors have very long stroke, so piston slap is not such a big problem.
Click to expand...
Good advice for a high performance bike?
Would you get on your bike in Brisbane, in it's current condition , and leave for Perth and expect to get there without break down?
If not, rethink the above advise.
A DNF is not fast...
dynodave
72 trophies on the shelf and 2 years club championship...... but what do I know?
 
Make a more efficient air pump, and as Jim says lighten up the rotating mass. Not cheap or particularly easy to do. A lot of the work is tedious, and details are where the power is made in my experience. I don't do it for a living though, so as Dave says, what the heck to I know.

Is it worth chasing more HP? If you like working with hand tools, and have some spare change, I think so. If turning wrenches is an annoying chore, and you have a very limited budget, leave the bike in stock trim and maintain it. A stock Norton 750 Commando makes enough power to kill ya any day of the week on the street.

I'll head back to the rubber room now. I see the attendant coming with the straight jacket.
 
jseng1 said:
If you want reliability along with performance then you have to reduce stresses on the motor by reducing the reciprocating weight (the shaking forces). The same forces cause wires to break and parts to fall off. They break cases, crankshafts and rods and are the reason Norton came up with the isolastic mounts.
Click to expand...
Not sure this is exactly 100% accurate.
Not many Atlas crankcases got broken that I'm aware of, con rods didn't break unless the oil to the crank was blocked, but I get your concept.
The orginal 750 engine did vibrate somewhat in the old f/bed frame, but they were sold with low 7.5: 1 dished pistons. The birth of the commando came about when Norton employed a new designer team who upped the compression raito to 9:1, to give it a power boost.
 
Bernhard said:
Not sure this is exactly 100% accurate.
Not many Atlas crankcases got broken that I'm aware of, con rods didn't break unless the oil to the crank was blocked, but I get your concept.
The orginal 750 engine did vibrate somewhat in the old f/bed frame, but they were sold with low 7.5: 1 dished pistons. The birth of the commando came about when Norton employed a new designer team who upped the compression raito to 9:1, to give it a power boost.
Click to expand...
"Not many atlas crankcases got broken" not sure about this statement
I've seen plenty of atlas crankcases broken
 
Bernhard said:
Not sure this is exactly 100% accurate.
Not many Atlas crankcases got broken that I'm aware of, con rods didn't break unless the oil to the crank was blocked, but I get your concept.
The orginal 750 engine did vibrate somewhat in the old f/bed frame, but they were sold with low 7.5: 1 dished pistons. The birth of the commando came about when Norton employed a new designer team who upped the compression raito to 9:1, to give it a power boost.
Click to expand...
I suspect the wide availability of improved petrol/gasoline influenced the decision as much as a new design team!
 
On the 750 engine it’s not the crankcase that Is the weak spot but the cylinder barrel base, especially on rebored engines. The 750 responds well to tuning until the base flange breaks. My advice is 9:1 compression, standard or 2s cam ( I love the combat cam in a 750) don’t worry too much about porting, the early heads flow just as well as the later 32mm ports. 32mm Amal’s on tapered manifolds. If all this is put together carefully will be fun on the road. Take care balancing the crank.
 
MYJOTA , what is the difference between the stock cam and the combat cam ?
what differences do they make ?
 
Status
Not open for further replies.

Similar threads

S
Modify Z Plates
Replies
17
Views
606
Onder
Onder
yooper trooper
CV Mods
Replies
5
Views
638
Deckard
Deckard
Tornado
MK3 Starter Mods Video
Replies
0
Views
433
Tornado
Tornado
S
Help Required-Rear Hub Rebuild!!
Replies
10
Views
595
Shelby-Right
Shelby-Right
Anvill
Seeking advice for misaligned head stud
2
Replies
21
Views
707
MichaelB
MichaelB
Back
Top