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B+Bogus · Dec 16, 2021

acotrel said:
If you have access to a decent foundry, it might be worth moving on to producing stronger crank-cases. That would allow the old type commando engine to rev higher without doing damage to itself. These days we can buy billet cranks and long steel rods with light pistons. But building a top end motor using the old parts is pretty unrealistic. The Fullauto head is good but the bottom end of the motor sucks. The usual failure from over-revving is a split in the drive-side case - through the bearing housing. It dictates that the older Commando motor must be tuned to deliver more torque, rather than power higher up the rev range.
If you could safely rev a long-stroke Commando motor to 9000 RPM, it would really go.
Balance factor would be important. But if you rebalance a Commando crank to suit 9000 RPM, the standard cases would probably fail due to the imbalance at lower revs.

Steve Maney started out with a beefed up drive side case many years ago (over 20?) before he went on to manufacture complete crankcase sets.
One of the key reasons for him taking a back seat was the foundry he was using decided it no longer wanted the work.
Andy Molnar is now manufacturing stronger cases, so not sure there's a gap in that market right now.

Just great that cylinder heads are now on their way back on the market

Madnorton · Dec 16, 2021

All the split cases I have seen are flawed from the casting process, they were gassed. You can spot this if choosing case to race with.

acotrel · Dec 16, 2021

I have got a set of caes in my shed to which I have welded a plate surrounding the drive side bearing because they were split. I will have a look to see if I can detect gassing. When I repared them I was not looking for a defect in the casting. With Hot Triumph Motors, the Puma crankcases were the way to go. I have a friend whowns a bike we built in the '70s. It has a Nourish crank, Puma cases and Carillo rods. It runs in Period 4 historic as a 750. He was won several historic championships with it. He still said to me 'I cannot beat the Nortons'. The only Triumph part in his motor is probably the cylinder head and rocker box castings. A 650 or 750 Triumph can run at 8000 RPM all day, as long as the crankcases are strong enough. Over the years, most of our 650 Triumphs have blown up and disappeared from racing.
With a Commando which has the right balance factor, the crankcases would probably cop 8000 RPM. But it might be expensive finding out you were wrong. With my own bike, my reservations might all be in my head. But I have purposely worked towards improving torque rather then horsepower. Nothing beats a larger number of firings per minute.

acotrel · Dec 16, 2021

Probably the best Norton twin was the 650SS ( Manxman) because the piston weight was lower. I watched Jack Forrest race one at Bathurst in about 1963. He beat all the Manxes as well as the Henderson Matchless, which was four-valve. The race was the Unlimited A grade. Jack was an international rider, but the other guys were not slow. I think the major problem with the Commando is the weight which is being thrown around inside the motor. A smaller capacity motor can be faster than a big one.

SteveA · Dec 16, 2021

acotrel said:
If you have access to a decent foundry, it might be worth moving on to producing stronger crank-cases. That would allow the old type commando engine to rev higher without doing damage to itself. These days we can buy billet cranks and long steel rods with light pistons. But building a top end motor using the old parts is pretty unrealistic. The Fullauto head is good but the bottom end of the motor sucks. The usual failure from over-revving is a split in the drive-side case - through the bearing housing. It dictates that the older Commando motor must be tuned to deliver more torque, rather than power higher up the rev range.
If you could safely rev a long-stroke Commando motor to 9000 RPM, it would really go.
Balance factor would be important. But if you rebalance a Commando crank to suit 9000 RPM, the standard cases would probably fail due to the imbalance at lower revs.

Through John we have new heads coming, new barrels coming, alternative new barrels and new crank cases already available from Andy Molnar, what is missing at the moment is a regular supplier for 89 mm and other stroke crankshafts.

With that you will be able to build new engines to your heart's content, or as usual, to the limit of your funding!

lcrken · Dec 16, 2021

acotrel said:
If you could safely rev a long-stroke Commando motor to 9000 RPM, it would really go.

I'm pretty sure that if you managed to rev an 89 mm stroke Commando twin to 9,000 rpm safely, you would have so much friction from the piston rings that you would have a serious horsepower loss. Might be handy in terms of saving a shift on the race track now and then, but using that as a regular shift point down the straights would be slower than using something closer to the horsepower peak. Using that high an rpm regularly would also probably accelerate cylinder bore wear. It would be nice to have an engine sturdy enough to live through 9,000 rpm use, but only from an overall reliability standpoint. I don't see any performance gain from it except with the shorter strokes that some Commando racers are now using.

Ken

G81 Can Cycle · Dec 16, 2021

ozcruiser said:
Very nice will they come with 30mm or 32mm inlet ports or both.

32mm inlet ports on both 850 and 750 The stock OEM ports on 750 are 30mm. So, this head will flow much better on the 750's. We are installing one now on a bike and looking to change the intake manifolds to 32mm to take advantage of these bigger ports (not sure if the stock 750 intake manifolds are 30mm or not). So, there is a good possibility that a 750 performance will be greatly improved with this head, 32mm manifolds, and 932 Amals.

G81 Can Cycle · Dec 16, 2021

Time Warp said:
It is good to see something was done with the 3/8" stud pitch . (The looks to be deformed insert and tail not so much if it is not a trick of the camera)
People will see what they want to see, perhaps something shiny for many, others will be looking closely at the engineering detail.
Let's

hope the as delivered exhaust guide to valve stem clearance is to spec especially if using Kibblewhite valves with uniform stem diameters (unless they will come with instructions to check that)

I truly hope this works out to be viable and that is, be profitable to be self driven, being a AU$1000 cheaper than the original heads supporters payed will help in that endeavour.
I will hope you have a crew who are not only passionate about this project but have the gumption and ability to dispatch a worthy product detail and pride wise.

A pity this thread has been derailed and hope it is not off putting to the the original poster.

I looked at the pictures of the thread insert. They look fine to me. These are Keenserts, which we believe are better than Heli-Coils or other inserts. They lock into the thread a little different than Heli-Coils, so that may be what you are seeing

G81 Can Cycle · Dec 16, 2021

worntorn said:
I didn't say it was easy, just that it might be easier for them than your average machine shop. The machine shops I've visited around our area have mostly old equipment, less capable stuff than I'm using for hobby work.

According to this, STS has 50+- CNC machines.

Plus a lot of other very expensive high tech equipment that one could not afford to own just to make Norton parts. I'll bet it comes in handy!

Yes, it is a good size shop. I sold it 2 years ago, but still manage the place. Right now, we are trying to get all the Norton stuff in our catalogue. That way it will continue to be made after I retire. Additionally, only about 60% of the work here is firearms, we are also a good size gear shop (we make gears). We make planetary gear reductions boxes for torque multiplication (we also make full gear sets, main and lay shafts, for the AMC box. These will be added to the catalogue soon). If you have seen our CNW Estart you will notice the drive train is gears instead of a chain like on the Alton. We did this because we make gears, and as a nod to the original Mark 3 drive system which is a gear train

acotrel · Dec 16, 2021

Most 650 and 750 cc Triumph twins use 82mm stroke. At 7000 RPM the 89mm stroke Commando motor is probably at the limit for piston speed. But a billet crank is not difficult to manufacture. With Jim Schmidts longer rods and light pistons, the motor would rev much higher. Triumph valve gear is not much different to Commando. With a slower lift rate cam, it can be run to 10,000 RPM. With the 82mm stroke, the Triumph motor still has plenty of torque. But it does not have the good cylinder head. I had hotted Triumphs for years, my Norton motor is much better. And it can only be the cylinder head which makes it so.
The new Fullauto head with the 32mm ports interests me. My 850 has 34mm carbs but 30mm ports. The first inch of the ports are tapered 2mm per side back to 30mm. The smaller ports are better if you are not revving the motor higher than 7000 RPM. Often the first thing we think of when hotting a motor is bigger ports. But once you have removed the metal, it is difficult to put it back on. - 'Been there done that'.

Madnorton · Dec 16, 2021

Yes, a billet crank is easy to make, but a bit more tricky to make it right.
Watch this space, hopefully the modelling and CAD data will be completed soon.

jseng1 · Dec 17, 2021

I would really like to see 3/8" x 16 TPI for the three head studs. Its a stronger thread than the finer British threads. It would be disappointing to see a compromise to a weaker thread pitch.

Same with the cylinders. The 3/8" 16 TPI ARP-613-2750 3/8-16 2.750 bolts from Summit racing would fit right in.

3/8 x16 is the thread pitch Maney used for the head to the cylinders and also the Factory for the cases at the cylinder base - and for good reason.

I would also love to see the intake valves reangled to 26 deg - even if using stock size valves. The valves are too close to each other in a Norton and valve clash is always a problem with performance cams. Spreading the valves would allow performance cams to have tighter lobe centers and result in increased performance. Then you could install bigger valves if you wanted by just opening the ports and seats (also provide intake seats with a larger OD to accommodate this). None of this would add to the expense of the head and it would make things better for everyone. Its what the factory should have done when they went from 650cc to 750.

acotrel · Dec 17, 2021

Once upon a time, we used to be able to make things in Australia. America is superior. Our engineers can fix farm machinery but not much else. Be careful with what capabilkity you have , because you can lose it easily due to neoliberalism and globalisation.
I feel excited by the posts on this subject, they give me hope that there will be a return to better things. It is really good that somebody has picked up the ball with the Fullauto head. Money is the root of all evil, but some things are worth doing, simply because they are good things to do.
'Quality does not cost - it pays' ?

seattle##gs · Dec 17, 2021

cliffa said:
John, thank you, that looks terrific !!

A question - would it be possible to supply them (maybe on special order) tapped for more modern 10mm plugs? I there are quite a few benefits but I cannot think of any downside.

What are the advantages of a 10mm spark plug over a 14 mm?

Schwany · Dec 17, 2021

The only place I can see smaller 30mm intake ports being a "performance advantage" on a Norton head is in town in a shopping mall parking lot. Same goes for smaller carburetion. Can't see it being a performance advantage. I can see it being good for mature riders that like to run smaller Amal carburetors, short shift, and not run their motors hard ever. I think the decision to use 32mm intake ports on the rebirth of the Full Auto 750 and 850 heads is perfect and the right thing to do. It's a very small increase in size and in my experience works better than a stock head with 30mm intake ports on a 750, but I'm nobody, so there is that to consider.

cliffa · Dec 17, 2021

seattle##gs said:
What are the advantages of a 10mm spark plug over a 14 mm?

I'm glad you asked.

Well, primarily, why not? as far as I know 10mm plugs weren't available back in 1967 & times have moved on.
You will have more metal around the valve seats, so there are benefits for tuning etc.
My gut feeling is that you are less likely to strip the thread (although I can't really offer any scientific evidence for that)
If you do strip one, you can go up to 12 or 14mm without inserts, but if you choose an insert you have more material to play with.

acotrel · Dec 17, 2021

What is needed is a bigger market to ameliorise the set-up costs for good parts. In my opinion the Commando engine is a very good race motor, But it has to be used in a certain way. It's advantages are it's massive torque and it's gentle power delivery. So it needs to go better in bends and corners. The faster you come out of a corner, the more horsepower the other guy must have to pass you before the end of the next straight. Even on big circuits, it is a matter of scale and gearing. Most guys do not take the low line into corners, braking as they go in until they reach about one third of the wat in - then grab the biggest hand-ful of throttle possible. You cannot do that with a bike which has peaky power delivery and understeers when you accelerate.

Eldert · Dec 18, 2021

seattle##gs said:
What are the advantages of a 10mm spark plug over a 14 mm?

you can move the 10 mm spark plug a little higher up in the combustion chamber .
and run a little less advance due to the better flame propagation . use a plug that protrudes a little like a CR9E .

Eldert

worntorn · Dec 18, 2021

You can carry more of the 10mm in your pocket.

Glen

Madnorton · Dec 18, 2021

Some of the above seem ideal mods for the road, but what ones will pass scritineering for racing.
I'm sure John will retail heads for the modders, but I suspect it would need some notice so machine steps could be left out so the head could be finished to each owners idea by the owner.

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