Narley ports for High HP Nort roadracer.

Here's some photos of the Narley ports (HD XR750) being roughed into a welded up Norton head. The work was performed by a machinist in Australia. Ports measure up to 44mm wide to get around the guide and about 28mm tall at one point. D shaped ports for the exhaust. This is for an all out screaming race motor on alcohol. He says that it revvs to 8500 RPM and that it feels like it wants to rev to 9000 but that will have to wait because its TEMPORARILY using a stock crank and cases - they are surviving (for now) only because of the lightweight pistons. Torque starts in above 4000RPM and keeps increasing as the RPMS climb. You won’t see this bike in the US – its down under. They just can’t seem to get enough down there. The owner/racer is very happy with it so far and is presently making a one piece crank for it. JSM parts include custom 14.5 to 1 CR lightweight domed Alky pistons, longer rods, 5mm oversize intake valves and 3mm oversize exhaust valves, Stage 3 cam with BSA lifters, Beehive springs. So far there is no hint of valve float but I would like to cut him a special cam before he goes for 9000RPM (if he really wants to rev it that high). Presently he is having a problem getting enough fuel into the mix. The Mikuni carbs aren’t flowing enough through the bowl and the plugs are white. Removing the main jets entirely wouldn’t even do it. He has drilled the float jet but he will also have to drill the fuel passages. This is the first "Narley port" type head in a Norton race bike bike that I know of so far. Hopefully there will be more to come.







Roughed out stage before finishing. The photos that were sent to me show the initial machining and do not represent the final dimensions of the "Narley ports". Many hours of hand porting were invested as well. The finished result may not exactly match the specs on the "Narley ports CD" but no one is complaining.

very impressive Jim. 9000rpm geez!!

Awesome Jim !! I love seeing this stuff, thx for posting it :mrgreen:

Is it possible that Fullauto could supply heads with enough extra material to machine these Harley XR ports without resorting to welding?

Of course. How many would you like to order?

Show me the dyno figures and how it will benefit road riders and I'll price it up.

If it would give me another 15 or 20 rear wheel horse power & even more low down grunt I'll order one now!

Fullauto said:

Show me the dyno figures and how it will benefit road riders and I'll price it up.

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Gives new meaning to the term Hogged Out.
With those extended intakes I would think a considerable amount of cutting/grinding/welding/fiddling with the stock Command frame will be required to get carbs to fit.
No?

BritTwit said:

Fullauto said:

Show me the dyno figures and how it will benefit road riders and I'll price it up.

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Gives new meaning to the term Hogged Out.
With those extended intakes I would think a considerable amount of cutting/grinding/welding/fiddling with the stock Command frame will be required to get carbs to fit.
No?

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Yes...but would probably be easy to fit on my Slimline/850mkII racer...dreaming now!!! 8)

Would you ride a commando engined bike on Daytona, if it was pulling 9000 RPM with standard crank, cases, rods and pistons ?

most any one that has much knowledge of nortons knows you would NEVER turn a stock crank, rods, pistons or cases anywhere near that RPM.

acotrel said:

Would you ride a commando engined bike on Daytona, if it was pulling 9000 RPM with standard crank, cases, rods and pistons ?

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Jim’s post indicates that the motor currently uses his lightweight pistons and rods. Perhaps the reduced mass of these components reduces the pounding of the crank and cases enough to account for the amazing reliability at 8500 RPM. Not sure I would have the courage to rev one of these motors that high, much less to 9000.

I can’t wait to hear how all this engine tech turns out on the track. I think if the port design works out to better power, and better power spread, it would be a desirable update for a new Fullauto head.

bill said:

most any one that has much knowledge of nortons knows you would NEVER turn a stock crank, rods, pistons or cases anywhere near that RPM.

acotrel said:

Would you ride a commando engined bike on Daytona, if it was pulling 9000 RPM with standard crank, cases, rods and pistons ?

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I certainly don't have much knowledge of Nortons, and when I fitted a Norton crank and rods into a Triumph racer a few years ago I had even less!

That bike ran strengthened unit T120 case and a stock Norton crank and rods (750 cdo I think). It gave good power as a result of a heavily re-worked head running a good squish band. I regularly revved it to 8500rpm!

The crank was fine, although I had to run the squish clearances bigger than I'd like to handle the flex.

But a rod broke, and increased my collection of interesting and expensive 'shrapnel art' ...!

I am sure no one knows this yet, but what sort of an exhaust is going to compliment such an intake?
What goes in must come out in a complimentary fashion, if you will.

The machine work shown above is only the start. A lot of hours were put into shaping and finishing these ports. Some compromises were made as usually happens as everyone has their own way of doing things.

Full Auto – to use such wide ports a blank head would need material filled in all the way to the head bolts that are nearest to the outside of the intake ports. The area in the middle between the in ports may as well be filled in solid for the necessary width and a central oil return drain will have to be installed with a hose leading to the timing cover. The entire FA in port would have to be raised. The higher floor is achieved by re-angling the intake manifolds so the port can arc upward to the sides of the guides in a broad smooth curve leading into the bowl. Its counter intuitive because the intake manifold must actually be more level and less down draft so the curve is longer, otherwise you end up with a bad tight curve just before the bowl. The sides are raised significantly around the guides to raise the port and bring the charge straight down onto the valve. An extreme example of this is shown below.



The above photo shows how material is left in front of the guide to prevent cracking. So going full auto would be expensive because it means buying an expensive head and then investing a lot more porting expense as well. The FA head would need an even higher port floor than it already has and about .1” less depth in the valve spring pocket cut as well as a smaller 1.1” diameter for the lightweight Beehive springs - all to give more material near the guide. Perhaps Ken could provide a FA head with more material where needed by removing sand from the casting etc. Until that happens, I and others will be starting with cheaper used heads. These stage 3 ports have no business on the street and its not going to have anywhere near the low end of a small port head. Its all about top end pass em on the straights and leave em behind power. The “Narley ports CD” has 3 different stages of porting and the milder, narrower stage one ports would work well in a hot street bike. But the milder ports are still raised and require welding. Welding up the port floor is the most difficult task. I’ve been working with a couple welders who can perform this operation it the tight spaces allowed.

The head being machined above is a Commando head and no it would not fit in an unmodified Commando frame. Note that I have fitted long manifolds and velocity stacks into a Commando frame by removing the frame gusset near the carbs. Narrow carbs help (CRS, PWK, MK2s). I would have bolted on the manifolds but each to his own. Note that he started with a 750 head, welded up the outside bolt holds and relocated them to fit 850 cylinders. Such a motor definitely needs a heavy duty lower end and I hope he gets that taken care of before it blows and ruins all his hard won head work. Way back when, I was able to use a stock crank with the flywheel diameter reduced to help keep it from exploding and the PTO shaft radiused to keep it from cracking but I was using shorter lightweight pistons and that makes all the difference in the world. I did reinforce the cases (this was before Maney cases were available). I revved that motor as high as it would go until I could hear the valves float (using shimmed to the max RD springs back then). It never blew but came very close. Now with the longer, lightweight bushless Carrillo rods the jerk stress is even more reduced and such a high revving motor is possible. To get XR750 type power its wise to look at everything from the HD point of view including the dual exhaust (more top end than a 2 to 1 ex). the intake length (10” total from head), the cam profile and lobe center timing. etc. If you miss any of these ingredients then you are defeating your own purpose. My objective is to put it all together and make it available for those who are bold enough to go where no one has gone before (or maybe someone has already).

Do we have any dyno results yet to show what sort of numbers these mods can produce in a Commando ?

Rohan said:

Do we have any dyno results yet to show what sort of numbers these mods can produce in a Commando ?

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No numbers yet, but the racer with the Narley head reports that the bike is significantly quicker than the previous version (full race Norton with roundish ports).

If you want dyno numbers then the thing to do is look at what the XR750 puts out. But to match XR750 dyno numbers you would have to match all the HD specs. No one has matched all the specs yet and the cam has yet to be copied (the cam is only mapped out so far). This is a work in progress. When some one gets everything right (more displacement is an option), and puts it on the dyno - then we will see some interesting numbers. If its a compromised motor for the street or because the builder made some short cuts, then the HP figures are going to be compromised as well.

jseng1 said:

If you want dyno numbers then the thing to do is look at what the XR750 puts out.

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So if we port our Commandos like a desmosedici, they will go like a desmosedici. ?
Wow !!
But we get your drift....

Be nice to see some numbers before we all start with the new casting, or welding and opening out ports though,
make sure its not just the beer talking. ?

The 4 valve per cylinder Rickman heads did not make Triumph 650s go much faster.

The 1930 Rudge with a 4 valve head was near unbeatable at the time, inc wins in the TT,
so maybe the (much later obviously) Rickman didn't so something right ?

A lot of folks have suggested if Rudge etc had had the $$$ to continue developing that path,
then manx nortons etc would have been obsolete even before they began.
Torque is where 4 valves really showed up back then, outright speed may not gain (much).
Be interesting to see the torque curve of the Rudge, wouldn'tit....

P.S. Triumphs claimed (CLAIMED) 58 bhp and 125 mph out of the TSS.
http://www.motorcycleclassics.com/class ... jzbea.aspx
That would appear to be quite a zip in performance over its 2 valve version ?

But we diverge, as usual.