Norton intake ports compared to Harley XR 750 (2013)

FWIW, the ignition on the ex-Hately bike was points and coil, with a custom points plate with the points cam running in its own ball bearing, and with Bendix points. That's what's under the red cover in the picture.

Ken

Thanks Ken.

Short Stroke.

That explains a lot regarding the 77 RWHP numbers cited earlier. The shorter stroke allows for a larger intake valve as well as greater mass flow before the practical limit for mean piston speed is reached.

I am running a modified Moldex crank in my ultra short stroke and as far as I am concerned, it is bullet proof.

I've got a couple of questions:
1. What do the figures obtained on a flow bench really mean when you are dealing with standing waves, harmonics between exhaust and inlet ports, and sonic speeds in ports ?
2. If you achieve a higher BHP on a dyno at high revs, does that mean the motor still pulls hard at all other parts of the rev range ?

When I ported my 850 motor, I did it with the Aermacchi Ala D'Oro 350 in mind and tapered the inlet ports from 34mm back to standard over the first 25mm from the manifolds. That Aermacchi was the best ever 350 single cylinder four stroke, and the inlet port was tapered to manage the dynamics. I suggest that if you increase top end power, and lose midrange (torque), you are quickly moving towards a mechanical failure with a commando engine. If you want short stroke, a Triumph 750 engine might be a better starting point? There is an old saying 'torque wins races'. I'm amazed at what my Seeley is like to ride , after years of riding short stroke 500cc Triumph, and conventional 650cc Triumph racers. It is bloody good stuff, and I'm just sorry that I didn't race it as soon as I had built it in 1978.

Note that Kenny's bike stays together with the help of lightweight pistons - Norton's never had it so smooth - more reliability is available now ever before.

Go back to my 1st post for a photo of the head (intake side).

Here's the exhaust D port info & molds.

Not the widening of both intake and ex port shape for getting the air around the sides of the guide & stem.

EX PORT
D shape flat on bottom with mild ridge leading to guide, roof is D shape with more ridge near guide tapering to nothing at pipe.
Oval shape when viewed from head side, D shape viewed from pipe side

33 ID near seat
maxes 42mm side to side at guide

24.5 minimum venturi top to bottom 1/2” from guide
flairs to 30 top to bottom at pipe 2-1/2” from valve
26mm top to bottom measured at guide
38mm side to side at pipe & ½” from pipe

harley ex port on left



harley port on top



photo ex side

No doubt the JS light weight pistons and rods contribute to Kenny's and others reliability.

Thanks again Jim for sharing the XR 750 stuff as we gain perspective here. I can see where the XR port would blow down better than the Norton and pumping losses are likely reduce when compared to the Norton EX port.

Really good stuff there.??

Thanks Jim, great thread.

I think Jim Comstock deserves credit for what he has done with his raised port floor and bringing a more ideal port shape to the Norton head. He started by attaching aluminum castings to the bottom of the stock Norton ports and then reporting from there - a lot of work. Too bad I don't have molds of his ports to show & compare. They are primarily designed for the street but there is plenty of metal there to reshape.

With the lightweight pistons and the heavy duty bottom ends now available - someone should try to emulate the all the specs of the Harley XR and see what happens (overheating may be too much). Last year a Norton 1000 (Gary Thwaites on Dave Watson's bike) not only finished all its races in England - it also won them all and with multicylinder bikes in the mix. See below.

That bike has had plenty of mentions here, already.

Unfortunately, no real detail of whats under that fairing.
Apart from a few stray component shots...

Is there detailed views anywhere of whats in it or under that fairing ?

A lot could depend on the circuit and the rider rather than outright top end horsepower. If it is 1000cc doesn't that mean the stroke is even longer than standard ? I thought the material between the bores of a commando engine limited it to 920cc with the standard stroke crank ?

The 1007 ( One - 007 Gedit ) uses the Royal Oilfiel STROKE 89 m.m. unless ive got it wrong . a few more revs than a R.E. though . :wink:

The norton head was quoted as being the most ' deep breathing ' in its era . in the efficency stakes .

Obviously a bit of developments going on here . after all the 60s were a time off now . More Power to you .

The mention of BENDIX C.B. points , I almost posted pics of a array of C.B. thingos on the setting them post .
Alledgedly the Works F-750 Triumph Triples suffered ailments with the nylon ones , heel wear and points bounce .
on the new fangeled el cheapo nylon suckers , and also had to use purloined American Tufnol based ones .

Just like the good old days . . .



these are probably horrible old 4CA ones , they bring out the 6CA & change the Tufnol to NYLON . fudge . progress indeed .

A machines never going to run right , if the ignition timings not spot on . I wonder why they go to electronic ignition .
:wink: :lol: :lol: :lol: I suppose the Magnetos olbsolete ( Lucas K2F anyway ) wondering what the part No/ application
is for the ' Bendix ' contact breakers to fit the 6CA , after modifications . Just for curiosities sake . though thered ba a
ready market for some decent points to replace the std. nylon excuse . Though it is possable to get them satisfactory ,
theres easier ways out . wouldnt recomend standard ign. except to a perfectionest or infinate patiance . 45 minutes to
set spot on. unless somethings not right . In which case it takes as long as it takes .There all in a rush ,
these days :lol: :lol:

SO , one of these heads , on a 80 m.m. stroke , will be fine at 8.000 rpm's , ? Designed to B R E A T H .

Rohan said:

That bike has had plenty of mentions here, already.

Unfortunately, no real detail of whats under that fairing.
Apart from a few stray component shots...

Is there detailed views anywhere of whats in it or under that fairing ?

Click to expand...

What I know is that its a Maney 1000 motor kit with the addition of 83mm JS lightweight pistons (240 grams) and JS stage 3 cam with lightweight lifters. These lighter components gave it an additional 1000 usable RPM. Also Seeley type Mk 2 chassis.

Maney Kit comprises of:

1. Crankcases
2. Crankshaft with 93mm stroke
3. Cylinder barrel
4. Pistons
5. Head gasket (thinner JS gasket)
6. Intermediate timing gear

I'm pretty sure it runs a TT gearbox.

Maney head Stage 3 with 5mm oversize inlet valves & 3mm oversize exhaust valves. Maney 2 to 1 exhaust.

After a year of racing it was torn down and found to have little or no noticeable wear on the engine components. I'm not even sure if they replaced the rings. It did melt a rear tire in one race.

Gordon Humphreys is the tuner/mechanic and he must be very good/meticulous.

The point I'm trying to make is that if the 1000 motor can stay together - then there should be a reliability increase nowdays with a fully pumped up 750 using current lightweight improved components (provided it doesn't overheat). Using the XR 750 port specs, intake & exhaust lengths etc on a de stroked Nort could bring new HP levels - possibly enough to blow off the 8 valve weslakes. Centered cam bearing has been engineered to eliminate flex and I think someone has even worked up roller lifters. Maybe use a 270 deg crank. It would take someone with deep pockets and a lot of ambition.

If I find out more I'll post it.

' It would take someone with deep pockets and a lot of ambition.''

'Making a silk purse out of a sow's ear' ? - Depends on the available race classes, however why would you go there - would it prove something ?
If you can get the bike really light, nimble handling with a strong flexible motor, and you gear it to suit the circuit - wouldn't that be better than fighting blow-ups ? I've found the most success when I am extremely well practiced and have got my head straight. Then you can ride around corners like there is no tomorrow, and get the available power on really early as you come out, without having the rear end step out. Nice to have 4 extra BHP at the top end, but do you really need it if the bike becomes stiff to ride ?
I really like Jim's long rods and short pistons, that is a really good way to go, however I am very careful not to over-port the head and destroy the midrange . That is the strength of the commando engine design.
I raced against a friend for 12 years with my short stroke 500cc Triumph. He had a 650 Triumph engined bike which I could never convincingly beat. It was never revved over 6,300 RPM, and it accelerated like lightning while pulling a very high overall gearing. Against any other similar capacity bike of the sixties, it is pretty much unbeatable, and it has never blown up. On a good day my own bike has lead a field containing H2 and Z900 Kawasakis. When it comes to ports, big is not necessarily better and it is difficult to make them smaller once they are big.

Alan getting on the power earlier after an apex pales to the thrills when a cycle allows you to leave darkies before you even begin to lean or turn forks, no skips or instants of acceleration hesitation, just dragster like hook up on 10-ish% best grip slippage. I am looking forward to seeing what that's like when power to spare so almost never able to go WOT or just spin out uselessly in a set up that can hook up more power on tire edges than them new age balloon things. Recent article commented on racer hanging Way Off to side in order to not lean so much he could put more power down on area of tire that could take it. That is approaching the entering into phase 5 power steering turning level. When ya got what it takes to handle this ya find out ya don't have to lean off center but got to be hooked accelerating over 1 G to out race the hi side crashing of course.

jseng1 said:

Rohan said:

That bike has had plenty of mentions here, already.

Unfortunately, no real detail of whats under that fairing.
Apart from a few stray component shots...

Is there detailed views anywhere of whats in it or under that fairing ?

Click to expand...

What I know is that its a Maney 1000 motor kit with the addition of 83mm JS lightweight pistons (240 grams) and JS stage 3 cam with lightweight lifters. These lighter components gave it an additional 1000 usable RPM. Also Seeley type Mk 2 chassis.

Maney Kit comprises of:

1. Crankcases
2. Crankshaft with 93mm stroke
3. Cylinder barrel
4. Pistons
5. Head gasket (thinner JS gasket)
6. Intermediate timing gear

I'm pretty sure it runs a TT gearbox.

Maney head Stage 3 with 5mm oversize inlet valves & 3mm oversize exhaust valves. Maney 2 to 1 exhaust.

After a year of racing it was torn down and found to have little or no noticeable wear on the engine components. I'm not even sure if they replaced the rings. It did melt a rear tire in one race.

Gordon Humphreys is the tuner/mechanic and he must be very good/meticulous.

The point I'm trying to make is that if the 1000 motor can stay together - then there should be a reliability increase nowdays with a fully pumped up 750 using current lightweight improved components (provided it doesn't overheat). Using the XR 750 port specs, intake & exhaust lengths etc on a de stroked Nort could bring new HP levels - possibly enough to blow off the 8 valve weslakes. Centered cam bearing has been engineered to eliminate flex and I think someone has even worked up roller lifters. Maybe use a 270 deg crank. It would take someone with deep pockets and a lot of ambition.

If I find out more I'll post it.

Click to expand...

Steve's 1007 cc kit also requires modifying the cylinder head to accommodate the wider bore spacing. To fit the larger 83 mm bore size, he moved the bore centers a couple of mm further apart, which also required moving the cylinder head bolt and cylinder through bolt locations. He modifies the Commando head to fit by relocating the head bolt holes and re-cutting the counterbores/squish areas to accommodate the larger bore diameter and wider bore spacing. The crankshaft has a wider flywheel to locate the rod journals properly. It's also possible to fit the 93 mm stroke crankshaft to a standard 850 engine by using a stock width flywheel. Using the 93 mm stroke with the 81 mm bore that is normally used for a 920 engine gives you 960 ccs. If you don't like the longer stroke, you can also build a 963 cc engine by fitting a standard 89 mm stroke crankshaft (using the wider flywheel) to the 1007 cc kit.

Ken

About 15 years ago I paid a visit to Greg Sanders, Long Beach, CA. Greg was the guy who built the one off V4 using two Commando Top Ends. He also was a former employee of Jerry Branch. He showed me a Commando head that had been transformed into a XR750 configuration on one side and still had the Norton geometry on the other. One of the benefits of working in a place like. I have not talked to him in some time. Anyone else been in touch with Greg or possibly seen the Franken Head?

Working on transition to retirement.
Rj Reynolds

How do you test a head like that - run it on one cylinder ??
Or was in the the works of being done both sides ?

Did you see what looked different ?

Thanks Jim and Ken for the details.
Its almost a new bike when all done, easy to see why its so strong.

Still be interesting to see under the fairing, if anyone has a naked shot.
(Is it legal to encourage that here these days ?!)

Rohan said:

How do you test a head like that - run it on one cylinder ??
Or was in the the works of being done both sides ?

Did you see what looked different ?

Click to expand...

Flow testing?

Interesting suggestion.

Anyone that has played with porting will know that what flows well on the bench and what works well on the track do not necessarily correlate. ?
As Aco mentioned earlier, pulse harmonics and bench flow testing do not necessarily produce the same results.

Manx Nortons etc and F1 race engines etc lifebloods come from harmonic tuning.
A number of race engines in recent times have those adjustable length inlet trumpets, low and high rev optimisation of inlet lengths.
Electronically computer controlled and driven, even...

Rohan said:

As Aco mentioned earlier, pulse harmonics and bench flow testing do not necessarily produce the same results.

Click to expand...

This is like saying you need to start the motor if you want to make real power.

Flow testing does not preclude tuning. In other words, no sh*t.