RH4 to RH10 JS Intake Port Sleeves

If you enjoy old motorcycles, never make a career out of fixing then for orther people. Money-motivation can kill enthusiasm.
One thing I have never done and would never do, is accept money for working on a motorcycle
 
In a previous post, I said 'do not speed on public roads'. I am a hypocrtie. That is the reason I do not ride a motorcycle on public roads. Where I live, if you lose one licence, you lose them all. It is 40 kilometres to the next town, and a mile to the supermarket.
I would love to own an original Commando, but all I could do with it, is keep it shiny.
There is something about them which is excellent. I would like to get one and change the gearbox. I think it would be a real buzz. Japanese bikes do not have 6 speeds for nothing. It would really get a Commando going.
A lot of things about Japanese motorcycles is propaganda. You do not need 4 valves per cylinder.
 
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acotrel said:
If you enjoy old motorcycles, never make a career out of fixing then for orther people. Money-motivation can kill enthusiasm.
One thing I have never done and would never do, is accept money for working on a motorcycle
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Alan, theres a lot of truth in all that and your welcome in my shop or load your bike in the van to the track anytime.
However I can tell you after a several year stint of mini mx with the grandson where I quickly became a go to guy to get a kid on the starting line that some will take advantage of you. When I'm not around the same folks will pay hundreds to get the same work done.

Back to the intake sleeves I have been doing similar work but not done yet. I'm not some kind of pro tuner but i've run a machining center for 40 years so I've seen some highly developed blown up car motors up to indy cars and while they ask why do you think it broke, can it be fixed, how do we stop from happening again I'm looking at port runners and valve pockets trying to figure out how they get so much power. A lot of them get twice the power from same size holes as a norton just shaped better. Its hard to describe how it all works so i'm putting some links to good reading on the subject. Kevin Cameron's book tells it best how to get a ratcheting effect from pressure change going from tapering runner to valve pocket to combustion chamber and how the same damps reversion.

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I bought a pair of these because the science of flow dynamics for a 32mm carb into a 30mm intake port has been proven for a Commando head. Norton did it in 1974 with the RH10 head with 32 to 30mm intake manifolds. These sleeves will do the same a little further downstream for Combats and RH4 850's. Only a dyno would tell you if the reduction in the manifolds or inside the intake port makes any difference. Then there's choice of carburetors, which I believe any 32mm carb would benefit with this change.
At $20, a bargain to improve midrange where we all live on the street.

Dubious it will make a big difference with single carb engines, but that's not something I'll ever bother with.
That's already a compromise in performance.
 
Deckard said:
I bought a pair of these because the science of flow dynamics for a 32mm carb into a 30mm intake port has been proven for a Commando head. Norton did it in 1974 with the RH10 head with 32 to 30mm intake manifolds. These sleeves will do the same a little further downstream for Combats and RH4 850's. Only a dyno would tell you if the reduction in the manifolds or inside the intake port makes any difference. Then there's choice of carburetors, which I believe any 32mm carb would benefit with this change.
At $20, a bargain to improve midrange where we all live on the street.

Dubious it will make a big difference with single carb engines, but that's not something I'll ever bother with.
That's already a compromise in performance.
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I've not noticed a compromise in performance with my single carb TM 40 flat slide pumper as yet
 
baz said:
I've not noticed a compromise in performance with my single carb TM 40 flat slide pumper as yet
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Good to hear. The majority of those who did the Mikuni conversion said they were smooth, but lost some top end.
 
Jim Comstock found that the flow restriction with the single carb conversion was in the manifold design.

"Yes, the short MAP and similar manifolds flow very poorly. That is what causes the loss of power with a single carb -it's not a restriction from having only one carb."

Glen
 
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A quick update, just pulled the carbs to play with some jetting and I figured I would check to see if the conversion tubes are still in place. Everything is exactly where it should be and they are still very much well sealed in place.

I am curious if anyone else is running these conversion tubes, and if they have tried running them with fuel that contains ethanol. If so what sealant are you using and have you had issues? I have not tired pump gas 91 octane yet with this setup, I plan on doing that soon.
 
I was planning to use the high heat silicone as suggested . That way if there isn't a power increase I could take them out again, albeit with some cleanup work needed to remove the silicone.

Glen
 
maaseyracer said:
A quick update, just pulled the carbs to play with some jetting and I figured I would check to see if the conversion tubes are still in place. Everything is exactly where it should be and they are still very much well sealed in place.

I am curious if anyone else is running these conversion tubes, and if they have tried running them with fuel that contains ethanol. If so what sealant are you using and have you had issues? I have not tired pump gas 91 octane yet with this setup, I plan on doing that syon.
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I just got two sets in the mail on Friday. Still need to get some Loctite 510 to hold them. I've got a trip in three/four days up to Muskoka so I'm going to hold off till I get back.
 
I installed a set of intake port sleeves on my mk3 yesterday, after giving the Loctite 510 24hrs to cure I have just been for a short ride to try them out.
My mk3 always felt a little lardy on the throttle response and I can say after fitting the sleeves the throttle response is way better in the midrange and it just builds revs a lot easier than previously. As to more power I cannot really say as my butt dyno is not that sensitive, but my initial feeling is that installing the sleeves on an Rh4 head is a no brainer due to the cheap cost and easy install.
So, I say 2 thumbs up to JS motorsport intake sleeves. 👍👍
 
Desmopower said:
I installed a set of intake port sleeves on my mk3 yesterday, after giving the Loctite 510 24hrs to cure I have just been for a short ride to try them out.
My mk3 always felt a little lardy on the throttle response and I can say after fitting the sleeves the throttle response is way better in the midrange and it just builds revs a lot easier than previously. As to more power I cannot really say as my butt dyno is not that sensitive, but my initial feeling is that installing the sleeves on an Rh4 head is a no brainer due to the cheap cost and easy install.
So, I say 2 thumbs up to JS motorsport intake sleeves. 👍👍
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I am impressed with your patience. I waited 30 mins tops for the loctite to cure. Glad to hear you had success with them.
 
A friend and I have ordered 2 sets of sleeves but are yet to install, with std 32mm concentrics did anybody need to change needle or jet settings?
 
possm said:
A friend and I have ordered 2 sets of sleeves but are yet to install, with std 32mm concentrics did anybody need to change needle or jet settings?
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I left my jetting as it was previously before the sleeves (Amal premiers) No issues at all with jetting.
 
BrianK said:
About to do this job. Just noticed the advice to remove the intake manifolds. Not hard to do, but why? Seems this could as easily be done with the manifolds in situ - with less potential damage to/need to replace manifold gaskets. Tx - B
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The manifolds are curved
The sleeves are shaped to the inlet ports I'd assume?
How would you get them in ?
 
baz said:
The manifolds are curved
The sleeves are shaped to the inlet ports I'd assume?
How would you get them in ?
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I know. Total early morning brain fart - I ran back to the keyboard to spare myself the embarassment but you were too quick for me!

(Even if it were otherwise possible, I realized during the job (now done, loctite curing) that the only way I was able to get the FCRs on way back when was to pre-assemble to the manifolds and then bolt the assembly to the heads. If they hadn't come from CNW, i.e., Norton experts, I'd've sworn they WOULD NOT FIT. But they do. Not a fun job but it's doable.)

Thanks - B
 
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I will mention this again for you Mikuni people...there is a company called Thunder Products which has done a lot of work on the simple round slide VM carbs and his inventions really works. The best item is very simple to install and requires NO fiddling around with jets. The main improvement is in low speed to mid range. It is called The Torque Wing (this NOT the swarup and is NOT a gimmick). It really works, I've used it for several years. Look it up on their website for more info.
 
BrianK said:
I know. Total early morning brain fart - I ran back to the keyboard to spare myself the embarassment but you were too quick for me!

(Even if it were otherwise possible, I realized during the job (now done, loctite curing) that the only way I was able to get the FCRs on way back when was to pre-assemble to the manifolds and then bolt the assembly to the heads. If they hadn't come from CNW, i.e., Norton experts, I'd've sworn they WOULD NOT FIT. But they do. Not a fun job but it's doable.)

Thanks - B
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We've all had moments like these 👍👍👍👍👍
 
seattle##gs said:
I will mention this again for you Mikuni people...there is a company called Thunder Products which has done a lot of work on the simple round slide VM carbs and his inventions really works. The best item is very simple to install and requires NO fiddling around with jets. The main improvement is in low speed to mid range. It is called The Torque Wing (this NOT the swarup and is NOT a gimmick). It really works, I've used it for several years. Look it up on their website for more info.
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this seems aimed at two strokes. How is it on Commandos?
 
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