WO 41/2 running rich

Douglas F Hutson · Joined: 08 Feb 2000 Posts: 2 Location: South Africa

I have a WO 41/2 fitted with Sloper carbs that runs very rich (black sooty exhaust) I've fitted the leaner needle/jets but they have not made much difference. Any ideas on how to fix the problem?

Robert Craven · Posted: Tue Jan 31, 2017 1:58 pm Post subject:

Do you really mean you've fitted leaner jets as well as needles? I don't think this is a normal change.
Assuming you have the normal 0.100" jets and haven't changed or renewed them, I wonder if the cork seals need renewing. (Or perhaps the jets have somehow got scored or worn and need replacement.)
In the past I've had problems with being unable to stop the carbs running too rich however far up I turned the adjusting nut, and found it was due to worn out sealing washers which seemed to be allowing too much fuel through at all times. Renewing them cured it.
Burlen sell special rubber seals which are said to be better than cork. I've bought some but haven't yet needed to install them.

John Murch · Posted: Tue Jan 31, 2017 2:34 pm Post subject:

Doug,
I totally agree with Robert's advice.
John

Paul Spencer · Posted: Tue Jan 31, 2017 5:51 pm Post subject:

I would look for the easy stuff first. When you set the mixture control to lean, are the jets moving up as far as they should?

Chris Card · Guest

Things to check:
Assuming that the jets and needles are not worn and that fuel pressure if using pumps is not overcoming the float chamber needle.
Remove the three screws holding the piston and carefully lift out the piston - with a straight edge check that the shoulders of the needles are level with the base of the piston.
With the piston out, turn on the pumps or open the autovac and see where the fuel level comes in relation to the top of the jet - it should be just below the top and not overflowing. If it is overflowing or is too low you need to adjust the collar on the float chamber needle.
Replace the pistons and when screwed down lift each piton and see that it falls smoothly an hits the bottom with a click. If it hangs up, you need to recentre the needle inthe jet by small movements of the large nut at the base of the jet.
If you are using pumps and you can't stop fuel overflowing the jet, you need an inline pressure regulator.
If you are on an autovac, make sure that it is working correctly and the internal valves are doing what they should. It may be that the autovac is flooding and fuel is being sucked back into the inlet manifold.
I assume that you have been sdjusting the mixture with the engine up to temp and that the jets are going fully home.
Most 4.5ls run well on a CV needle and I get about 19 mpg.

Chris Very Happy

Douglas F Hutson · Joined: 08 Feb 2000 Posts: 2 Location: South Africa

Paul Spencer · Posted: Tue Feb 07, 2017 11:38 am Post subject:

Hi Chris,

Your comment has finally prompted me to look at the adjustment of my own slopers. I had always adjusted them in the past by the "lift the piston and listen" method. But I recently had to reattach one float and the car is hard to start in cold weather. So I removed the pistons and looked at the jets, where I couldn't see any fuel. Even with the mixture set to rich, I couldn't see any fuel. Although the float chambers look full, I should probably run the engine (I am on autovac) to be certain, but I thought I would check something first. At a full rich setting (about 1/2mm of movement in my case), would you expect the fuel to be right at the top of the jet? Or even bulging out over it? I though this might help me get the "normal" running position right.

John Murch · Posted: Tue Feb 07, 2017 1:17 pm Post subject:

Paul,
did you mean 1/2 (0.5) mm? I'm sure mine move a lot more than that.
John.

Paul Spencer · Posted: Tue Feb 07, 2017 2:39 pm Post subject:

Yes - 0.5mm. Because of the free play in the system from having 90 year-old parts, I adjusted it until the jets moved fully home when set to fully lean. I then asked someone, and he thought this was the normal amount of movement. But I am sure mine used to be more too. So that could explain the difficulty with cold starting. But I would like to get the fully lean adjustment right first.

Chris Card · Guest

Hi Paul

Running the engine first, shouldn't help solve your problem as the autovac should be in it's normal cold starting state (unless you've drained it). With the autovac you have a constant fuel pressure, unlike a pump, which pulses.
I've just checked my jet movement between weak and rich and it is about 2mm.
What I suggest you do, is this:
Disconnect the mixture controlling linkage between the two carbs so that adjustment to one carb jet doesn't affect the other.
Screw both mixture adjustment nuts up to fully weak, counting the flats and then return them to the average position, so that both jets are set up the same.
Now look to see where the fuel level comes in the jets - they may be the same, or different, and the only adjustment is with the collars on the float chamber needles. If the fuel is too low in the jet, you need to move the collar up the needle so that the float chamber will fill more before the needle shuts off the flow; and vice versa. Only make small movements - if, with the needle pressed down on the jet, you make a small file mark on the exposed top of the needle against the lid of the float chamber to mark it's position, this will give you a guide.
Some collars are soldered to the needles, which makes life difficult - mine are a press fit and can be gently tapped up or down and I then "rivet" them tight, as you don't want them coming loose while on the road.
When you've got the float levels correct with fuel at the top of the jets you can then do your final mixture adjustment in the normal way by lifting the piston and listening to the change in engine speed.
Once both carbs are right, press the jets up to make sure and then reconnect the link adjusted in length to remove any slack. Then, hopefully all will be well. I've assumed that the needles and seats are not unduly worn and that they stop the fuel flow from the autovac when the needle is down, also that the carbs are balanced with the butterflies opening in parallel - I have a cheap vacuum gauge device that I got from Holdens, which measures the suck from the carbs at fast tickover and you adjust the throttle linkage between the two carbs to get the suck more or less equal.

Chris

Paul Spencer · Posted: Thu Feb 09, 2017 9:15 am Post subject:

Hi Chris,

That's what I was afraid you would say! The only reason I was thinking of running the engine is that, with the recent salting of roads and lack of rain to wash the salt away, I have not started the car for a couple of months and there is a slight danger the autovac has run low. It shouldn't as there is a fuel tap so any evaporation from the float chambers should not drain the autovac, but it was just in case ...

A little while back, one float chamber would occasionally flood. A well-known 4 cylinder WO expert reground the float needle, which made it worse. At that point we realised that the problem had been that the float was too low on the needle, so he moved it up. I don't think he went through the setting up you said. His argument is that it didn't matter as long as the fuel level was not too high as the venturi effect would always give the same amount of fuel in the mixture. This may well be correct (I had the lambda checked a while back, and it was correct although it looks as though the fuel level in the jets is too low), but this does not allow for setting a richer mixture for cold starting.

Anyway - the floats are silver soldered, so I am not sure I can do this myself. I can see a trip to an expert coming on. I think I should also get rid of the free play in the choke mechanism so I can get more movement - that should just be a case of drilling out and bigger pins.

Chris Card · Guest

Hi Paul,

QUOTE: "His argument is that it didn't matter as long as the fuel level was not too high as the venturi effect would always give the same amount of fuel in the mixture."

I think that may be true once the engine is running, but I suspect that at "cranking speed" there would not be enough suck for efficient cold starting.

Chris

Chris Card · Guest

I've just had to replace the jets, corks and needles (CV) in my Slopers. I found that the idle speed had become erratic and the engine was still running rich with the jet adjustment at fully weak.

Not a difficult job to do, and the difference in running is significant. The jets are now set at about 7 "flats" from fully weak and this gives a nice consistent 500rpm idle, with plenty of power on the road and good throttle response. Getting the needles centred in the jets took a bit of "fiddle" time.

Off to France on Monday!

Chris
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