Solex Expert Level Question

[Rich Goold]

Hello all, I am getting into the real fine tuning here and have a problem with fuel injector nozzle quantities. Carbs are Solex 40P11 freshly rebuilt. New accelerator pump diaphragms, new injector nozzles #40, new pump jets #50. The accelerator pump rods are disconnected so this isn't just an adjustment issue. I am using the Porsche measuring vial and have measured many times. Three of the injectors measure .65 and one measures .75. (Porsche recommends .45 to .65). Do any of the experts have any idea what would cause this imbalance? Is there a solution to get them balanced? Maybe use different size pump jets and/or injector nozzles? Am I looking for too much precision here? Should I just ignore the variance between .65 and .75?

[Martin Benade]

How are you getting a repeatable volume? The length of the pump rod is the adjustment to set volume.

Have you tried swapping the jets to see if the different volumes move with them?

[Phil Planck]

Could be crud in nozzles. Take apart and clean. Dont lose check balls.
Split or solid shaft?

[Rich Goold]

These are solid shaft. The nozzles are all brand new so there is no crud in thetr

[John Brooks]

If you have a set of jet reamers, you can measure the hole in the end of the nozzle. I slide a reamer in the hole and slowly turn it counter clockwise until it’s seated. Then I put my thumb hail on the reamer to mark the nozzle face. Then I measure the spot with a micrometer or a dial thickness gauge. The higher flow nozzle must have a larger hole where it’s crimped on the end.
You can ream all the nozzles to the same size, then adjust the output with the linkage stroke.

Stahlwille 11085 Jet reamers, P/N. ST74310001

[Rich Goold]

Hello Martin, the pump rods are disconnected and I am manually moving the pump levers for 2 full strokes.

I have tried swapping the pump jets but the quantity doesn’t change. It is always too much for cylinder #4

[Rich Goold]

John,

All of the nozzles are brand new # 40. I have moved them around to different cylinders but I still get the same measured quantities. Cylinder # 4 is always too much.

[Mike Wilson]

New nozzles...I'd make sure they are the same size as John suggested.

Mike

[David Jones]

Below the accel pump jets mounts on split shaft Solex carbs there are brass cylinders that limit accel pump output. Are they present in all the circuits.

[Phil Planck]

Rich
Why not try adjusting output per the manual? Maybe when you get down to .35 cc per 2 strokes that difference will disappear.

[Olivier Auvray]

1) different pump jets (one by side).
2) different nozzle sizes (input and output holes)
3) different brass balls weight
4) as mentionned previously, dirt/dust somewhere.

But the difference is not huge.

[Dave Erickson]

Hello Martin, the pump rods are disconnected and I am manually moving the pump levers for 2 full strokes.

I have tried swapping the pump jets but the quantity doesn’t change. It is always too much for cylinder #4

Its more likely to be the nozzles. Try swapping the nozzles between carburetors, left to left (cyl 4 to cyl 2). Make sure you can hear the check valve ball bearing rattling in each nozzle, sometimes they get stuck in one place. Check the fiber gasket below each nozzle, maybe there is a piece of fiber blocking the passage. You will probably need a new pair of gaskets.

[Rich Goold]

The nozzles are all new but I rotated them anyway, no change. Cylinder #4 still getting too much fuel. Nozzle gaskets are new as well.

[Rich Goold]

David, the brass cylinders to limit output for each circuit might be my problem but I don’t recall seeing anything like that when I rebuilt the carbs. My carbs are solid shaft, should they have the brass cylinders as well?

[David Jones]

Not in solid shaft carbs.