RH4 to RH10 JS Intake Port Sleeves

colin davie said:

The previous owner of my mk2a bored out the rh10 inlet ports to 32mm which he said was a standard modification, When i took the bike to Norman White to have a PW3 cam fitted he said no no no, it needs that smaller bore for improved intake velocity,
who would you put your money on ?
Colin

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Agreed Colin, in fact having said he would do some work, when Norman realised it had Hemmings mod's he refused to touch it.

Which is fine TBH, but I am where I am and from that point of view, I'll carry on down the road I'm on and see what happens.

I haven't had a Commando since the early 80s, been playing with Triumphs and NRE/Weslakes really and lots of different opinions out there it seems!

Oh yes, and I have found that most of that rock solid handed down thru the ages opinion is based on zero fact when put to any kind of actual test.

Glen

I wiould like to congratulate whoever mafe the skleeves for the ports. It had crossed my mind that it could be done, however I dismissed it.
I have always had the opinion thet once the head was over-ported, it is stuffed.
Many years ago, in the 1950s in Melbourne, the Bray brothers had a Manx fitted with a pushrod Matchless motor in place of the Manx motor. It was not ported big, but was much higher geaared than the Manxes. It was competitive.
Keith Compbell was an Australian rider who was killed while racing in Europe, when he was married to Geoff Duke's sister. I never saw him or his brother George race. However Geasrge has a son named Keith who is Geoff Dukes nephew. Betwen them they race a featherbed with a pushrod Matchless motior. One day I happened to see the motor with the carburetor off. The inlet port was huge. I simply said to them, If you play with a two valve JAWA engine, you will probably start where you have finidhed with the Matchless motor.
Neil Street used to spend his British summers with the Australian riders at Poole Speedway. He built motors. When he was back in Melbourne for our summer, the Compbells bought two Jawa motors from him.
First time Keith raced with the Jawa motor, it was unmodified, he beat Bob Jolly for a win, who was riding one of Ken Mcintosh's Molnar engined Manx Nortons.
With the Jawa engines - on British speway a rule was introduced which reduced the opermitted inlet port size by one millimetre. I do not know the reason that rule was introduced. However the port size changes the motor's power delivery characteristic.
When that happens with a road race bike, the gearbox requirement is different.

When I was a kid, we always ported the cylinderr head to get more power, and we also raised the rear suspension to get better cornering. - How wrong can you be ?

Schwany said:

In my experience (always subject to extreme criticism) midrange moves up a few RPM with slightly larger intake ports and higher lift and longer duration cam profiles. Sensible short shifting street riders relying on torque and trying to make their motors lope along and last forever would probably get the most out of this sleeve modification. I doubt many road racers would see any huge benefit unless they only raced on racetracks with Winton turn 2's in them. Or only raced in a field filled with overweight out of shape retirees going a lot slower.

You can also get slightly better midrange spending countless hours tuning carburetion, exhaust, and making intake track modifications, as well as using smaller diameter carburetors at the cost of top end. A lot of parts can be touched up to improve flow. The sleeve is certainly cheaper than buying new carburetors and taking all that time to tune though.

Comnoz is a sharp tuner, but I seriously doubt his racebike had 30mm intake ports.

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This wouldn't be so much for loping along as for ripping up those long steep mountain grades in BC, Washington, Montana and Wyoming. Mechanical sympathy just won't allow 3 rd gear screaming for miles and miles . Top gear and 4500- 5000 revs can get you past a long line of holiday traffic in a hurry.
It takes a lot of power though, especially if you are loaded two up + luggage. These inserts could help a bit with that.

Glen

worntorn said:

This wouldn't be so much for loping along as for ripping up those long steep mountain grades in BC, Washington, Montana and Wyoming. Mechanical sympathy just won't allow 3 rd gear screaming for miles and miles . Top gear and 4500- 5000 revs can get you past a long line of holiday traffic in a hurry.
It takes a lot of power though, especially if you are loaded two up + luggage. These inserts could help a bit with that.

Glen

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Good example.

You must be in fantastic shape as well as quick if you can go over tight mountain passes in 4th and stay in a useful pulling powerband. Given my BS modifications I think I would be over geared now. 30mm sleeves wouldn't help. A stock cam and smaller carburetors might though.

If I were in 4th gear at 4500-5000 RPM I'd be in deep doo doo flying around on tight mountain passes. The long sweepers would be OK. However, I would be in 3rd gear a lot if the curves tightened up even though my intake ports are only .5mm larger in radius than a 30mm hole would be. 3rd gear in that RPM range is not excessive screaming with my gearing and around 60-65mph I think. I have not tried going over the Cascades with the taller gearing and all my latest changes. It may end up being an eye opener.

I don't have passenger pegs on my Norton, and an old Norton twin is in all truth the last bike on the planet I would tour on even one up. If I were going to tour on a motorcycle again, I'd get another new BMW, and I'd probably need a new wife to go with it. A BMW is something I consider adequate handling, comfortable, and reliable. 300 mile out and back one up days I do on the Norton, because I know I'm coming home to my garage full of tools at the end of the day. Going across the country, not a chance. Spoiled by riding much better hardware in the past. Maybe I'm just too negative.

worntorn said:

Oh yes, and I have found that most of that rock solid handed down thru the ages opinion is based on zero fact when put to any kind of actual test.

Glen

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For sure Glen, but in this case it doesn't appear to be "Folklore" but some form of disagreement about the way of doing things, between Mick Hemmings and Norman White.

Paul (850 Commando.) said:

For sure Glen, but in this case it doesn't appear to be "Folklore" but some form of disagreement about the way of doing things, between Mick Hemmings and Norman White.

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But did Mick Hemmings do his own porting ?
I only ask because when I bought a ported big valve head from George Mezilini of Mez porting
He told me that he'd done the big valve conversions for Mick
And George was a big fan of big ports and bathtub heads
So I wonder if George also did the porting ?
Sadly neither of them are with us anymore to ask

Paul (850 Commando.) said:

For sure Glen, but in this case it doesn't appear to be "Folklore" but some form of disagreement about the way of doing things, between Mick Hemmings and Norman White.

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I think both of those fellows gave great advice on repairing Commandos. Strange that they would have such a disagreement!
I've got Norman's book and have used Mick's videos. I didn't notice any glaring differences in the instructions , but there must be at least one point of contention.


Glen

Schwany said:

Good example.

You must be in fantastic shape as well as quick if you can go over tight mountain passes in 4th and stay in a useful pulling powerband. Given my BS modifications I think I would be over geared now. 30mm sleeves wouldn't help. A stock cam and smaller carburetors might though.

If I were in 4th gear at 4500-5000 RPM I'd be in deep doo doo flying around on tight mountain passes. The long sweepers would be OK. However, I would be in 3rd gear a lot if the curves tightened up even though my intake ports are only .5mm larger in radius than a 30mm hole would be. 3rd gear in that RPM range is not excessive screaming with my gearing and around 60-65mph I think. I have not tried going over the Cascades with the taller gearing and all my latest changes. It may end up being an eye opener.

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We have 4 big fairly fast mountain highways in BC. They have a few twisty sections but most of the big long hauls are just easy sweepers. A fat man on a Goldwing could ride them quickly. I think one of those units passed me on the last outing.

There are some big hills in Washington and Idaho that fit that billing as well. White Bird Pass in Idaho comes to mind.
Definitely a mid to upper midrange hill.
We also have a number of really twisty secondary mountain highways. One really can't use the full power of a standard 850 on those. Well, maybe a GP rider could.

Glen

worntorn said:

I think both of those fellows gave great advice on repairing Commandos. Strange that they would have such a disagreement!
I've got Norman's book and have used Mick's videos. I didn't notice any glaring differences in the instructions , but there must be at least one point of contention.


Glen

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I've got the greatest respect for both of them Glen and met them both while racing, hence I bought the head when I saw it advertised, as I'd already spoken with Mick and he wasn't doing them anymore, so I was a little surprised TBH.

However I've already got the 33mm carbs as well, so (To a point.) my path is now dictated.

LOL doesn't mean I won't change my mind later of course!!!

Three things work together - engine torque, overall gearing and the internal gearbox ratios.
If you are usung a normal Commando gearbox, the rarios are not set up to give you maximum acceleration. THey are set up four touring. NIgel's five speed gearbox would probably allowe a quick downshift for passing traffic. So torque is not sucha big issue, even if the bike is high geared. With wider ratios, the downshift is usually too large. When you start comparing the effects of larger and smaller ports, you probably do not allow for the fact that one change iin set-up creates the need for another.
I tried racing with the standard Norton box - the bike waa too slow, On every gearchange I lost too many revs. Once you lose revs you have to waith for them to return, and that is where port size is important. Smaller ports give you more torque, so your engine revives better.
However on a big circuit where you use more top end power, bigger ports can be better, because you usually run higher in the rev range towards the ends of thwe strasights.. With a Commando, engine if you set the overall gearing lower, ithe bike does not usually accelerate faster, especially when you use the normal box. High overall gearing and closer internal ratios is usually better than lower gearing and wider internal ratios.. However some people do not seem to like changing gear.

Bigger ports give you more top end, but Commando engines ahould not be revved high unless the crank has been revbalanced. What has really surprised me is how fast a Commando engined bike can really be. My Seeley 850 is much quicker in corners than most other bikes in its class, and it stays with the lead bunch to the ends of the straights. So when it oversteers when gassed hard in corners, it has a distinct advantage.
If you come onto the straights 10 MPH faster, that is less acceleration which is needed doen the straights, to keep up. However with larger ports, I would come out of the corners slower. When you race, there is a point in the corners where you stop braking and start accelerasting. With my bike that point is usually very early in the corners. So a big burst of torque at that point is very important. Due to the trail, my bike stays more upright in corners.
Wherever you are, different terrain suits different bikes differently. With a big race circuit, the other bikes would get a bit too far ahead of me towards the ends of the straights.
Do not speed on public roads.

acotrel said:

Do not speed on public roads.

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Speeding now days is definitely risky but there are or were places on public roads where it can be done. You should have been in California in the 1980's and 90's. Lot of countryside with well maintained roads to check the top speed of a new ride on, as well as enjoy very fast sweepers and some on and off camber tight corners. Nobody around to run into. It was fun for a lot of riders. Occasionally somebody would get in over their head trying to keep up, but you can kill yourself riding anywhere if you make a mistake.

My mate John Feakes was an ex-pat Pom. Before he died a while back, I told him ' I think we have lived in the best time ever'. When I was a kid, there was no speed limit on Australian country roads, and it was also more difficult to get booked in cities. In those days, we could register almost anything. When I went racing. many of us built our own race bikes. I don't think it will ever be so good again. Everybody's mindset has changed. Every day, I become more of an anachronism. I really notivce the difference in the way people think these days. Their mindsets seem to be more self-limiting.. I have been spoiled - I only ever did things in which I had a genuine interest, and I usually achieved.
It is really strange, I have no religion and I am not afraid of death, but I don't handle grief at all well. If you can believe they are all up there looking down, things are probably much better.
What is important when you die , is how you are remembered. So do not waste your time making money without leaving something substantial behind when you go.
I still have it in mind to make an on-board Youtube video. Just to leave a picture of what a Commando engine can do in the right frame.
I am not bragging, but you need to see it to believe it. - 'It is so bad that it is good'.

Schwany said:

Speeding now days is definitely risky but there are or were places on public roads where it can be done. You should have been in California in the 1980's and 90's. Lot of countryside with well maintained roads to check the top speed of a new ride on, as well as enjoy very fast sweepers and some on and off camber tight corners. Nobody around to run into. It was fun for a lot of riders. Occasionally somebody would get in over their head trying to keep up, but you can kill yourself riding anywhere if you make a mistake.

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It is much easier to make a mistake on public roads than on a race track. I never ride on my reflexes. For something to crash me, it has to happen extremely rapidly. Racing looks fast, but the relatuive speeds are usually very slow, It is very rare that you ever really blitz another rider. There are only about 6 ways you can crash a race bike, and I have done them all. Proactive is always better than reactive. During a race, you can usually see a crash coming miles ahead, on public roads they can happen anywhere. I did not race until I was 29. Then it was too late, but at least I was sane.

Intake port sleeves?

In this life, everything is relevant to everything else. Why wouls ypu make a road bike go faster, when you can more easoly buy one which is faster already ?
I could have bought a GSXR750 instead of building my Seelery 850. Sometoimes the journey might be more importasnt than the destination/

acotrel said:

In this life, everything is relevant to everything else. Why wouls ypu make a road bike go faster, when you can more easoly buy one which is faster already ?
I could have bought a GSXR750 instead of building my Seelery 850. Sometoimes the journey might be more importasnt than the destination/

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Because you want to ride an old Norton, hear the sound of it and get to look at it when you park it after riding. That doesn't mean that you cannot make it work a bit better and have a little more fun with it.

Glen

I am 81 and spend a lot of time remembering and thinking. I cannot thiink of many things I could have done better. I started with very little and ended-up with suffiecient to keep me happy. I think the key to my happiness is my approach to life. When I was young, I played with oild motorcycles in my father's shed. I had two jobs in the evening whichg paid for my hobby. Most of the kids in my year 12 at high school became meduicat dcctors - 90 out of 300. However I had a happy childhood - when I should haave been studyiing, I was building race motors with one of my friends. When I went to work, I only ever applied for jobs in which I had a genuine interest, and because I was studying part-tiime, I always got the best jobs.
When you play with old motorcycles they change your mindset in a way which gives great pleasure from woek. I have always had jobs which I loved. Genuine interest helps people live longer.
The only thing which really hurts me these days is grief. Never leave it too late to visit your friends.
I do not believe money-motivated people are ever happy.
Medicare, suprtannuarion, fair pay the pennxion AND education are important. However we need to recognise the patterns which represent cause and effect.-