RH4 to RH10 JS Intake Port Sleeves

Fast Eddie said:
I recall him saying the difference was much greater Glen. The velocity in the low and mid range was much higher with the RH10 but the increased flow of the RH4 was more than the engine needed, hence they performed (more or less) the same at the top end.

Different engine sizes, and tunes, will of course behave differently though.
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You are correct, I found the discussion.
He said that the stock RH10 made around 3 or 4 horsepower more than the RH4 at 4000 rpm and that the heads were about tied for peak hp.
That is roughly a 10 percent gain at 4000, so quite substantial.
There is very little information out there on tuning for more midrange. Almost everything I have found on tuning Commandos is all about the top end, often at the expense of the 4000 rpm stuff. Dunstall's book comes to mind. It makes sense, without extra top end you won't win. If the midrange suffers, just use the gearbox and keep the revs up.
That's fine for racing but not great on the road.

I have a spare RH10 head here. I was going to have it ported for the 920 but might just try it in stock form on the 850 on dyno hill. The head needs rebuilding first.

Glen
 
Comnoz became very skilled in tuning for the street IMO.

His work on RH10s is fantastic. The results on mine were basically staggering !

Didn’t stop me putting a Maney Stage 3 on the track toys though !
 
Yes, I find that Jim's info is very useful for my goals. I follow it closely. Also LCR Ken has a lot of knowhow with Nortons, particularly the 920 size. He helped me out quite a bit with the 920.

I recently contacted Herb Becker about porting a head for the 920 like he did for my 650ss, as it has a really nice midrange pull.
He isn't taking on any work now, but in any case we were on totally different wave lengths. He is definitely a top end guy!
One of his recent projects was a 7.5 hp J.A.P side valve rototiller engine. He modded it to 20 + hp:)
 
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I trust both the Jims on the smaller ports being best on the street. I actually think my little P11 Norton motor was friendlier on the street with Amal 930's, the small stock ports, and the stock gearing. Unfortunately, clearly remembering the 1970's is difficult for me. Random flashes of doing really dumb stuff is about all I get.

Good point about tuning for midrange being ignored for the most part. Best I shoot for in the midrange is nice linear smooth running. Very hard to have it all especially with too much carburetion like I have. I think midrange is really short on my motor. Midrange might be when I'm off the throttle. Kidding. I need a tach. Mostly guessing what the RPMs are.

I have a basically new spare head on the bench that has 30mm intake ports. Unfortunately, I think the intake floor is too low to be good at high RPM and needs to be raised a little. I have no clue what RH number is it. All I know is it is a Commando 750 head I got off the shelf at Raber's shop. I'm heading off topic again. Stopping

Thanks to maaseyracer for starting this thread. I did wonder about the sleeves.
 
seattle##gs said:
Please explain the process of installing these sleeves. I haven't heard of these before.
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1. Remove carburetors and intake manifolds.
2. Clean intake ports with Acetone, carb cleaner, or your chemical of choice.
3. Mark the short end center with a sharpie so you can line up the tube with the valve guide.
4. Cover exterior of tube in a thin film of sealant (i used loctite 510).
5. Slide into the intake tubes.
6. Wipe off excess.
7. Rotate to align the valve guide with your sharpie mark
8. Reinstall intake manifolds and carbs.
9. Allow time to dry, Loctite 510 takes a minimum of 30 mins. I gave it that before riding, it did not move after 30 mins.

A note that should be made, is that there may be a better sealant than loctite 510, a buddy of mine who is an ex indy car mechanic and now builds custom race cars suggested it so I went with it. If you know of something better I would suggest using it.
 
Midrange can also be improved by advancing the camshaft 5 - 8 deg.


RH4 to RH10 JS Intake Port Sleeves

Inlet valve will close sooner, and the exhaust valve will open sooner, which may make more noise.
 
maaseyracer said:
1. Remove carburetors and intake manifolds.
2. Clean intake ports with Acetone, carb cleaner, or your chemical of choice.
3. Mark the short end center with a sharpie so you can line up the tube with the valve guide.
4. Cover exterior of tube in a thin film of sealant (i used loctite 510).
5. Slide into the intake tubes.
6. Wipe off excess.
7. Rotate to align the valve guide with your sharpie mark
8. Reinstall intake manifolds and carbs.
9. Allow time to dry, Loctite 510 takes a minimum of 30 mins. I gave it that before riding, it did not move after 30 mins.

A note that should be made, is that there may be a better sealant than loctite 510, a buddy of mine who is an ex indy car mechanic and now builds custom race cars suggested it so I went with it. If you know of something better I would suggest using it.
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Are the sleeves commercially available, or are they homemade?
 
I am surprised that Norton produced a Commando cylinderr head in which the inlet ports were too big. I would have thought they would be a long way ahead of the game with their level of experience. Perhaps they believed the Commando would have a power band which was higher up in the rev range ? Were Atlas ports that big ?
I think that when designing the Command, Norton were probably working backwards. What they were designing was intended to become a commuter, not a sports bike.
An Atlas is a different concept to a Commando. My mate has an Atlas with which he has won Allpowers A grade road races against 1970s Kawasakis.
 
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Before trying the rh10 it would be interesting to try a pair of these on Dyno hill.
I suspect that for maximum effect the tapered 32mm to 30mm inlet stubs should be used, but that could be another experiment. Maybe the straight 32 hitting 30 might work, as with Roland Pike and the Goldstar.
 
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worntorn said:
Before trying the rh10 it would be interesting to try a pair of these on Dyno hill.
I suspect that for maximum effect the tapered 32mm to 30mm inlet stubs should be used, but that could be another experiment. Maybe the straight 32 hitting 30 might work, as with Roland Pike and the Goldstar.
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Glen, see pic in post 1 of this thread, they come with a taper, so you’d use your stock 32mm manifolds.
 
So they are somewhat different than what happens with the rh 10.
That could be better, worse, or the same!
Will have to give it a try.

Glen
 
acotrel said:
I am surprised that Norton produced a Commando cylinderr head in which the inlet ports were too big. I would have thought they would be a long way ahead of the game with their level of experience. Perhaps they believed the Commando would have a power band which was higher up in the rev range ? Were Atlas ports that big ?
I think that when designing the Command, Norton were probably working backwards. What they were designing was intended to become a commuter, not a sports bike.
An Atlas is a different concept to a Commando. My mate has an Atlas with which he has won Allpowers A grade road races against 1970s Kawasakis.
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How many more times Al
The commando is tuned version of an atlas engine
Hence the flat top high compression pistons in a commando
 
worntorn said:
So they are somewhat different than what happens with the rh 10.
That could be better, worse, or the same!
Will have to give it a try.

Glen
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Yes, I don’t think these can fully claim to replicate a RH10 in all regards. Nevertheless it should be enough to tell you whether or not it’s a step forwards or not.

Actually, I’d be thinking your RH4 would be better suited to the 920 (perhaps with bigger inlet valves), and the RH10 to your 850… easy for me to say though… I’m not doing the work !!
 
I was thinking the stock rh 10 on the 920 is working really well giving that 100 to 135 kmh accel on the hill. Of course a lot of that is the reduced weight.
The 850 with rh4 does 100 to 113kmh now , which isn't bad at all, but when you are passing and there is a semi coming at you, more is better!
Mostly it is just fun farting about with this stuff to see the results.

Glen
 
cliffa said:
Yep, https://jsmotorsport.com/product/in...erting-32mm-850-rh4-heads-to-30mm-rh10-ports/

I wonder how much shipping is these days though.
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Probably more than the cost of the parts I suspect.

Had a look though and as my head was ORIGINALLY an RH10, but has a 33mm Hemmings gas flow/big valve conversion, I think I'll see how things work out.
Already got Jims 33mm carbs/manifolds/JS2 cam kit etc anyway so..............
There is a mismatch between head and manifolds and I haven't decided yet how I will address that.
 
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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