RH4 To Narley Port Conversion Tubes

After a ton of research, trial, error, failure, frustration, and figuring it out I have finally got to the functional prototyping stage of a conversion tube that helps an RH4 head get close to the Narley Ports documented by Jim Schmidt.

I have spent a good amount of time reading and modeling Jim's XR750 to Norton port documentation and communicating with Jim to get this to where it is. The idea is continuation on the idea from Jim Schmidts work on the RH10 Conversion tubes. I elected to get first round of prototypes 3D printed in aluminum and these are now in their second revision and are being run presently in my MK3 Norton. The goal is to increase the velocity into the port, develop a bit more torque down low and carry on up high as well.

With a third revision underway, I am feeling much better about sharing what I have been up to.






Sending files out via email then receiving these in the mail a week later was a trip:






Removal of the old RH10 conversion tubes was simple. A bit of heat from a torch and a tig welding glove had them out in no time. I cleaned the port with acetone, let it dry used Loctite 510 on the new sleeve and installed.



This is all new territory for me and I am still shocked that this actually fit let alone worked as well as it does. Crazy to think how much time and thought goes into something like this. There is a lot to unpack about how it runs after install, idle is quieter and I was able to reduce my idle running a JS2 cam (which like a high idle) down to around 1100 to 1200 rpm from 1400-ish. Starting is easier and time to settle into a running idle is faster. However, when you get on the throttle is when you start to notice things. I immediately noticed a good chunk of low end and midrange and when the cam comes on it is properly fast, it pulls beautifully to 7500 rpm (probably beyond as well). Tons of torque, tons of pull, finding

I am still refining these and plan another revision to get these things to be a closer fit there is still some playing I am doing. A lot of attention has been paid to the cross sectional area and I am working on a slightly more refined fit and dealing with 3D printing specific issues in the next round of prototyping. Curious to hear feedback, this has been a ton of fun to work on and I have already started a couple more Norton projects as well.

Very nice. There is a lot of work that goes into things like this. I marvel at what can be done with 3D printing. I've used 3D printing for magneto parts that can't be found anymore. I'd like to be added to the list when they become available.

I'm also very interested in them if they become available

Here is a JS port template lined up in the port. Fit is exact.

Nice work there sir !

Are you doing anything with the intake manifolds or leaving them alone?

Most of the intake tract squeezing I'm doing is in the intake manifolds going from 35mm FCR to 31.5mm intake ports. The work is for a not leaned forward engine solution, so mostly not relevant for Commando guys. I'm not seeing much change at low RPM. I am seeing a little more hit earlier from the JS2 cam.

Are you having to make any small tuning changes to your carburetion after installing the RH4 port reducers?

Is that a “guide” dog?

But seriously, nice work!!

The talent on this web site continues to impress.
Nice Work Sir...

Schwany said:

Are you doing anything with the intake manifolds or leaving them alone?

Most of the intake tract squeezing I'm doing is in the intake manifolds going from 35mm FCR to 31.5mm intake ports. The work is for a not leaned forward engine solution, so mostly not relevant for Commando guys. I'm not seeing much change at low RPM. I am seeing a little more hit earlier from the JS2 cam.

Are you having to make any small tuning changes to your carburetion after installing the RH4 port reducers?

Click to expand...

There are a couple challenges with integrating into the intake manifold not all intake manifolds are the same, and not all intake manifolds are cast well enough to fit right each time. The fit also has to be fairly tight, and the real issue is 3D printing is more like casting than CNC, so those factors are hard to control for two bodies. The shape is not easy to extend because the complexities of the curves and the cross sectional changes to get the shape. The advantage is I can really control the cross sectional area within the confines of the port. I do have a mock up version that extends into a manifold being printed for a BSA gold star that extends about an inch or two outside of the intake port for a webco style 3in extension, curve and shape is very different on that one. However, I am machining the manifold, so I can control the issues on that end. I take it your intake manifolds are straight and not curved?

I just ordered a "richer" cutaway slide on the Keihin CR carbs, which most likely means a leaner idle jet and different needles and positions. I have already switched to the richest needle you can get and i am slightly lean off idle and good from 1/4 throttle on. Obvious statement, the needle change helped the power come on. I was surprised that I needed to jet, but I guess that is what happens with increased air speed.

maaseyracer said:

There are a couple challenges with integrating into the intake manifold not all intake manifolds are the same, and not all intake manifolds are cast well enough to fit right each time. The fit also has to be fairly tight, and the real issue is 3D printing is more like casting than CNC, so those factors are hard to control for two bodies. The shape is not easy to extend because the complexities of the curves and the cross sectional changes to get the shape. The advantage is I can really control the cross sectional area within the confines of the port. I do have a mock up version that extends into a manifold being printed for a BSA gold star that extends about an inch or two outside of the intake port for a webco style 3in extension, curve and shape is very different on that one. However, I am machining the manifold, so I can control the issues on that end. I take it your intake manifolds are straight and not curved?

I just ordered a "richer" cutaway slide on the Keihin CR carbs, which most likely means a leaner idle jet and different needles and positions. I have already switched to the richest needle you can get and i am slightly lean off idle and good from 1/4 throttle on. Obvious statement, the needle change helped the power come on. I was surprised that I needed to jet, but I guess that is what happens with increased air speed.

Click to expand...

The intake manifolds I'm using are modified Commando intake manifolds. They are curved, cut, and then reshaped inside. I'm doing all the work by hand and only for use on my P11.

Hard to tell they are curved looking at this pic, but that's the only one I have that has them bolted to my head.



I've had to do some tuning just extending the manifolds 1/4". That and the fact that people might be under the impression that this stuff just gets bolted on and they are done is why I asked.

Nice work by the way.

maaseyracer said:

Here is a JS port template lined up in the port. Fit is exact.

Click to expand...

That's some really nice work there!

Two quick questions, how did your modified port compare to the JS sleeve that you removed. Also, how did the JS sleeve compare to the stock RH4 port.

Thanks,
Pete

Deets55 said:

That's some really nice work there!

Two quick questions, how did your modified port compare to the JS sleeve that you removed. Also, how did the JS sleeve compare to the stock RH4 port.

Thanks,
Pete

Click to expand...

First the JS Sleeve is brilliant. The JS sleeve is great improvement in torque and power delivery and does not require a rejet. My comments on the JS sleeve was that it was subtle at first, and when I removed the JS sleeve it and went back was not so subtle and I could not wait to get it back in there. The JS RH10 sleeve refines the RH4 port, improves driveability, and highlights the RH4 ports low velocity.

This 3D printed attempt at dropping a Narley port into a Norton is like doing the JS sleeve twice before rejetting, it has a lot more impact after my rejet and I am still working on refining the jetting which may change things more.

The beauty of this is that the RH4 has a reputation of being the worst of the Norton Heads, and these two sleeves really give it a shot of being something good.

maaseyracer said:

First the JS Sleeve is brilliant. The JS sleeve is great improvement in torque and power delivery and does not require a rejet. My comments on the JS sleeve was that it was subtle at first, and when I removed the JS sleeve it and went back was not so subtle and I could not wait to get it back in there. The JS RH10 sleeve refines the RH4 port, improves driveability, and highlights the RH4 ports low velocity.

This 3D printed attempt at dropping a Narley port into a Norton is like doing the JS sleeve twice before rejetting, it has a lot more impact after my rejet and I am still working on refining the jetting which may change things more.

The beauty of this is that the RH4 has a reputation of being the worst of the Norton Heads, and these two sleeves really give it a shot of being something good.

Click to expand...

Thank you, I have a set of JS sleeves I intend to install as soon as I get back from the INOA Rally, not messing with anything right now. Looking forward to seeing how you make out with you future experiments. Was hoping Glen would test the JS sleeves but I think he is still feeling the effects of the mad cow (sorry Glen couldn’t resist).
Good luck, I think you’re on to something really good there.
Pete

Pete, I am thinking of fitting and testing the sleeves soon, if I get some time.
Unfortunately my wife has been going thru Chemo ( didnt work) and is going for CAR T treatment next. I've been looking after her, not much time for motorcycles this year.

Glen

worntorn said:

Pete, I am thinking of fitting and testing the sleeves soon, if I get some time.
Unfortunately my wife has been going thru Chemo ( didnt work) and is going for CAR T treatment next. I've been looking after her, not much time for motorcycles this year.

Glen

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Good luck, best wishes.

worntorn said:

Pete, I am thinking of fitting and testing the sleeves soon, if I get some time.
Unfortunately my wife has been going thru Chemo ( didnt work) and is going for CAR T treatment next. I've been looking after her, not much time for motorcycles this year.

Glen

Click to expand...

Sorry to hear that Glen.

Let the bikes wait.

Best wishes to Mrs Glen.

Schwany said:

Are you doing anything with the intake manifolds or leaving them alone?

Most of the intake tract squeezing I'm doing is in the intake manifolds going from 35mm FCR to 31.5mm intake ports. The work is for a not leaned forward engine solution, so mostly not relevant for Commando guys. I'm not seeing much change at low RPM. I am seeing a little more hit earlier from the JS2 cam.

Are you having to make any small tuning changes to your carburetion after installing the RH4 port reducers?

Click to expand...

The taper on the needles compensates for loss of vacuum by providing more fuel. With a smaller port a slower taper needle should be needed to keep the mixture lean enough to get best power. The motor sucks harder on the jets. The slightest bit too rich on the needle jet is too much. A gearing change might also be needed, if the torque peak moves.

worntorn said:

Pete, I am thinking of fitting and testing the sleeves soon, if I get some time.
Unfortunately my wife has been going thru Chemo ( didnt work) and is going for CAR T treatment next. I've been looking after her, not much time for motorcycles this year.

Glen

Click to expand...

You have my sympathy, caring for our ladies always takes precedence. My wife recently had an injury which put her in a wheel chair. Most of us probably go along blissfully unaware of what other people experience. I hope your wife has value in her life, while she is with us. Make every day a winner.

worntorn said:

Pete, I am thinking of fitting and testing the sleeves soon, if I get some time.
Unfortunately my wife has been going thru Chemo ( didnt work) and is going for CAR T treatment next. I've been looking after her, not much time for motorcycles this year.

Glen

Click to expand...

Very sorry to read this
Best wishes with her treatment

Over-porting cylinder heads is probably a common mistake. I did it to my 500cc short stroke Triumph, when I was seeking more torque. I think it was because I had seen the inlet port of a Manx. - Stupid ? It did not really matter so much because the power band was always very high in the rev range. A 2 into 1 exhaust fixed the torque problem and made the bike ridable.
I was watching a video yesterday about the 500cc Aprilia Moto GP bike, in which the engine was made from F1 car parts. It was extremely fast but totally impractical. It could not be ridden, because it tried to kill the rider.