It's a long way to 920 type(rary)

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Hi there, from Yves on another thread yesterday, this looks *much* better:

Great day to day: I put the 920 big valves Seeley Codo on a dyno again, first time after the tuning from the inlets, you remember how disapointed I was after the first dyno run before the tuning of the head 62 HP and no torque...
But to day: 69.17 HP on the back weel and a max torque 71.6
The temperature was 30 degrees celsius and you can see on the curve from the analyzer that the mixture was way to rich.



It's a long way to 920 type(rary)


It's a long way to 920 type(rary)


Yves
 
As you can see on the A/F ratio the mixture is way to ritch, for sure around 4.500 RPM, so I will go down with the needle to have it leaner, as you can see on the graphs also the torque and HP go's down at 4.500 also, so let's try
Yves
 
As you can see on the A/F ratio the mixture is way to ritch, for sure around 4.500 RPM, so I will go down with the needle to have it leaner, as you can see on the graphs also the torque and HP go's down at 4.500 also, so let's try
Yves
Nice to see the great power numbers and I’m sure you’re breathing easier now. Perhaps a night out with your favorite girl, Stella Artois, to celebrate?

Regarding the A/F ratio, assuming the dyno pass is conducted at full throttle, the needle should be fully withdrawn from the needle jet and should have no influence on the fuel mixture. Perhaps you meant "go down with the main jet to have it leaner"?

At full throttle the fuel mixture should be solely controlled by the main jet and air correction jet. I could see that if a mismatch of needle and needle jet were employed, where a long, large dia needle was not fully withdrawn from the needle jet at WOT, the needle circuit could then control the fuel mixture, but with normal selection of needle components this should not be the case. If this were the case (needle and needle jet controlling fuel mixture at WOT), you should be able to remove the main jet from the carb and observe no effect on mixture strength, since it would then be solely metered by the needle circuit.

The fuel curve looks like it might benefit from a larger air correction jet, to both delay recruitment of the main circuit and lean it slightly, and a smaller main jet to get up to the correct A/F ratio. Eager to hear how things work out as you keep dialing it in.
 
Nice to see the great power numbers and I’m sure you’re breathing easier now. Perhaps a night out with your favorite girl, Stella Artois, to celebrate?

Regarding the A/F ratio, assuming the dyno pass is conducted at full throttle, the needle should be fully withdrawn from the needle jet and should have no influence on the fuel mixture. Perhaps you meant "go down with the main jet to have it leaner"?

At full throttle the fuel mixture should be solely controlled by the main jet and air correction jet. I could see that if a mismatch of needle and needle jet were employed, where a long, large dia needle was not fully withdrawn from the needle jet at WOT, the needle circuit could then control the fuel mixture, but with normal selection of needle components this should not be the case. If this were the case (needle and needle jet controlling fuel mixture at WOT), you should be able to remove the main jet from the carb and observe no effect on mixture strength, since it would then be solely metered by the needle circuit.

The fuel curve looks like it might benefit from a larger air correction jet, to both delay recruitment of the main circuit and lean it slightly, and a smaller main jet to get up to the correct A/F ratio. Eager to hear how things work out as you keep dialing it in.
Hi WZ 507,
First of all, I never drink a drop of alcool
The thing I try to do first is make it leaner at 4500 RPM, later I will work on the air jet and main jet, at the moment the main jet is 8 points larger as before the changes on the engine and I keep the air jet like it was before
The other thing is that the FCR have a aceleration pump, so on the dyno you must keep the throttle open at low RPM to avoid a fals reading becouse of the injection of extra fuel.
 
Hello Yves, didn't you say earlier in the thread that the bike felt great when you were riding it. Much better than before etc... Well I was wondering if it being a little rich might not be such a bad thing out on the road. It is still a new motor and needs to be run a bunch to get everything seating and bedded in and so forth. I will add that I don't have anywhere near as much experience with engines as you or jagabruno or ludwig or nigel or most of the other guys here, but lean is bad right and too lean is dangerous. Just thinking outloud...Cj
 
A 70 HP commando engine for the street is impressive Yves, once you get the fuel mixture adjusted, I bet you get a few more HP's from that adjustment too... How do you measure fuel/air mixture??? an O2 sensor in the exhaust pipe???
 
I just spoke with Yves...he has tweaked his FCR 35's a tad leaner and he reports Warp 8 -grade acceleration. Watch this space for his colourful comments.

(He has very kindly offered me to try out his spaceship, which I'll do next week...hehehe).
 
Yves,
Based on my own playing around on the dyno, that richness could easily be costing you 3-4 bhp I think...
 
A 70 HP commando engine for the street is impressive Yves, once you get the fuel mixture adjusted, I bet you get a few more HP's from that adjustment too... How do you measure fuel/air mixture??? an O2 sensor in the exhaust pipe???
Hi There, The mixture is analized on the dyno with a Lambda sensor in the exhaust. To day I was working on the FCR: I lower the main jet with 8 points, put the needle clips one notch higher, and go down on the pilot jet with a few points, probably to match becouse after adjustement of the idle speed when you rev the bike in neutral and release the throttle the revs hang up a few hunderd RPM above idle speed, then drop to idle, this is a sign that the idle mixture is to lean with the smaller pilot jets, I try to compensate with turning out two turns on the fuel screw, it was better but not perfect, I have to order new pilots jets, a size between the old one and the new one.
I did a road test ride with the Seeley and I gat the feeling that the torque was better from 3K on, difficult to say becouse we speak about 2 or 3HP, we will see on the dyno
soon...
Anyway, when you take a turn in thirt of even in fourth or fifth gear and you open to WOT, you feel the Seeley living, is like sitting on a wild horse, but so far I keep it under control.
At the moment I have a question, some persons claim to find 100HP on a Codo engine without turbo or blower, if I see what you need to do to find 70HP, I am asking my self
what to do to find the 30 Hp left ???
Yves
 
See the 84ok links in the above post and note what's already been achieved by Herb Becker. Beyond that - To get another 30 HP you might have to copy the characteristics of the Harley XR 750 because that's the most powerful pushrod twin valve. They get 90 to 100 hp out of a 750cc. For starters you have to move the valves so they are further apart (not just re-angle). You need .250" between the valves when they are on their seats and that means welding up the port bowls and re-shaping everything. When you get .250" between the valves then you can use wild cams with 100 deg lobe centers (the only way to realize a Nortons full potential). Then you need longer rocker arms to fit the new valve locations and to give you more lift (increased rocker arm ratio) with the available Norton cams. The longer rocker arm is available but that's another story.

You'll have to go to a JS3 or Sifton 480 cam and twin free breathing exhaust pipes. You'll need 10-1/2" length from the end of the velocity stack to the head.

It won't be cheap and it will take lots of time and development - but the technology exists - it just needs to be applied. Most of it is already laid out with the "Narley ports". This would be breaking new ground as no one has taken a Norton this far. The head would be very expensive with many hours of "Cobrahead" port shaping and the installation of huge valves. There would be so much modification that you may as well start with a stock 750 head.
 
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I think that achieving another 30bhp would require work that made the bike unsuitable, or at least unenjoyable, on the road.

Huge cams, huge ports, even huger carbs, huge CR, and huge revs!
 
I think that achieving another 30bhp would require work that made the bike unsuitable, or at least unenjoyable, on the road.

Huge cams, huge ports, even huger carbs, huge CR, and huge revs!
You dam right Nigel, I will keep it like this
To day I discover that the Alton alternator was not working anymore, no charge! I give Paul from Alton a call and he will send me a new stator and rotor, I hope for free...
I will receive it at friday, the bike will be ready for the WE
Yves
 
Yes it would be a bit wild for the street. The other option is Nitrous. See 920 land speed racer on Nitrous below. Not for city cruising.

It's a long way to 920 type(rary)
 
I seem to remember reading somewhere that Steve Maney was getting 100hp out his race bikes (and that's a race bike not a street going beauty that you want to spend time on)
 
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