Manx Norton’s have more in common with Moto GP bikes than we might think…

It is difficult to improve on perfection. I have often wondered how they got them to steer. It could not have been by chance.

I do not believe it is possible to improve on Commando ports. There are always trade offs.

acotrel said:

It is difficult to improve on perfection. I have often wondered how they got them to steer. It could not have been by chance.

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I wouldn’t quite call them perfect, but not to worry, I’m glad that we’re finally agreeing !

acotrel said:

It is difficult to improve on perfection. I have often wondered how they got them to steer. It could not have been by chance.

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Commando heads were mass produced, to a budget, by a company already on its knees. To state they can’t be improved for performance gain is obviously just click bait !

What you pick up on the merry go round you lose on the hurdy gurdy.

The biggest mistake is enlarging the ports

Burgs said:

Good question Fast Eddie, it would be interesting to know what they are getting out of the new shorter stroke engines, Norton tried a few different bore and stroke combinations but stuck with the basically square design at the end, although no money to play with.

My thoughts are the newer aftermarket engines have gained a bit from the extra revs they can safely rev to, that gives you a bit more to play with, extra gears help a lot, when they brought in the clutch starts I was still slipping the clutch when the front runners, using 5 speed boxes were nearly out of sight at the starts.

Spent a day with with Jack Carruthers (Kels Dad) checking over my Manx engine, and he said that if Kel was going for the money he used to over rev the Norton, but they would have to check and replace the valve springs after the meet, in a normal GP meeting he would hold the revs to 7250.

I don't think there would be a great HP gain but maybe more flexibility due to wider torque range which results in an easier ride but quicker.

I would like to know what torque they are getting out of the latest speedway 500cc engines as they certainly hoot along.

Burgs

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Comparing the latest 500 speedway is like chalk and cheese they don't run on pump fuel, have total oil loss system, and don't have 4/5/6 speed boxes. Otherwise a speedway engine would, in thir present state of tune, leave a Manx behind . ........

Mike40M said:

You still have the modern noise limitations, silencers steals horsepower.
Mine has 11:1 CR at .030" squish, needs double spark plug gaskets to keep plug gap.
Intend to run a dyno test this winter if time allows.

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That is the opposite of what happened when the ACU imposed those noise reduction cans for classic 500s!

Fast Eddie said:

I’m not entirely sure what you’re getting at? Of course, if you reduce the weight and increase the power (of anything) you’ll increase the power to weight ratio!

Although I didn’t call it out specifically, I was referring to a standard weight, standard power mk111.

But even with your figures, you’d still need 73 REAR WHEEL hp to keep up with the Manx…

And I think we both know that although that’s possible, there ain’t many of them in real life !

My point was simply by way of comparison, for anyone who enjoys their stock MK111… imagine what it would accelerate like with a little over double the horse power. Cos that’s what a modern Manx must be like!

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Didn't someone called Paul Dunstall with his rider Ray Pickrell on the "Drainpipe" 750cc win considerably against the Manxs and other 500 singles in the 1960s?

acotrel said:

The biggest mistake is enlarging the ports

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A LOT of improvements can be made to ports without enlarging them.

Read Comnoz‘ head flow testing thread.

Mike40M said:

You still have the modern noise limitations, silencers steals horsepower.
Mine has 11:1 CR at .030" squish, needs double spark plug gaskets to keep plug gap.
Intend to run a dyno test this winter if time allows.

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From conversations I’ve had, the 4 valver is a big improvement even though it’s relatively un-developed. Actually, the biggest gain is reliability (not what I’d have thought) due to the lighter valves and springs, greater valve to valve and valve to piston clearances, etc. And, as a side note, they are almost impossible to tell apart from a 2 valver.

As most of us know, a 4 valve head allows both greater flow and velocity, which should therefore allow for both greater power and torque. But the main advantage of the 4 valve Manx head does appear to be higher (and safer) revs. Higher revs with the same BMEP = more power.

But as a race bike with a well spaced 6 speed box, a lot of torque and a super wide power band really just isn’t necessary. The 4 valver I rode was amazingly enjoyable and engaging to ride, with ample power spread to easily keep it in the right gear (6 to choose from). However, get it in the wrong gear and you know about it !

An interesting side effect of the noise regs is they’ve led to the development of pipes which give much smoother power delivery without any megaphone-itis etc.

We have one very knowledgable forum member (who prefers to avoid too much forum argy-bargy) who has had extremely good results, going in a different way to most, with even longer exhaust pipes. So I’d say there’s more development potential there too.

A 2 into 1 exhaust system is better for cornering. Faster into the straights.

acotrel said:

A 2 into 1 exhaust system is better for cornering. Faster into the straights.

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On a Manx

storm42 said:

At the last Cadwell meet, Andy Molnar's Manx best lap was 1:48.53. Tim Horton on his ex Gary Thwaites 1007cc Seeley Commando best lap was 1:51.26. Tim and Andy can both ride fast, but the Manx won.

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Really enjoyed my first season riding British bikes.
Started to gel with my Commando at back end of season, my benchmark was Andy Molnar. I managed a 1.49.9 at best that weekend.
Getting closer to the front now. Andy’s a really good and fair rider, Jason Markham too on that BSA twin cam.
Roll on next season

Barkersegg said:

Really enjoyed my first season riding British bikes.
Started to gel with my Commando at back end of season, my benchmark was Andy Molnar. I managed a 1.49.9 at best that weekend.
Getting closer to the front now. Andy’s a really good and fair rider, Jason Markham too on that BSA twin cam.
Roll on next season

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Sent you a PM mate…

Fast Eddie said:

On a Manx

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Twin port exhausts on a single went out with button-up boots. They never made any sense. But seriously, a two into one exhaust on a Commando is much better in corners. That smooth power delivery is essential for faster cornering. Even with a lumpy race cam a two into one exhaust is better, as long as there is no restriction at the collector or beyond.