Flavia Vignale Carb adjustment

[the.cern]

I need some help please.
I had a wonderful drive last Saturday from Essex to North Wales, calling in at Tyn Y Cornel to touch base with the Welsh Run and then on up to Llanrwst. The car ran beautifully, although it was a tad nippy at 6am with the hood down. A total of some 320 miles.
A quick look round the car this morning revealed a sooty exhaust and, on investigation, four rather black and  sooty spark plugs. My question is, how is the mixture adjusted on the Solex 32 PAIA 8 carburettor?
Please can anyone help me before I have to drive back to Essex at the weekend?

                                                         Andy

[simonandjuliet]

Is the choke closing properly ? I presume you start her with full choke and then close when warm ?

[Jaydub]

Hi Andy, the mixture is adjusted by the volume screw at the base of the carburettor. It is the one with a spring under the head of the slotted screw. Ideally, carburettor adjustment is carried out after checking and setting plug gaps, contact breaker gap, ignition timing and valve clearances. Assuming they are all correct and the choke lever is fully closed as Simon suggested, bring the engine up to normal temperature, adjust the idle speed to approx 750- 850 RPM and then screw the volume screw clockwise ( inwards) to weaken the mixture. If as you suggest, it is running too rich. the idle speed will increase. Continue turning the screw slowly in or out to obtain the fastest idle speed. Readjust the idle speed as necessary with the idle speed screw. If that doesn`t fix it you may have another fault with the carburettor such as an incorrect float level etc.
Good Luck.

[stanley sweet]

Could it be something as simple as a dirty air filter? I take it each bank of cylinders on the flat 4 has its own carb? Seems strange that both carbs would go out of adjustment at the same time if all 4 plugs are sooty.

[lancialulu]

Could it be something as simple as a dirty air filter? I take it each bank of cylinders on the flat 4 has its own carb? Seems strange that both carbs would go out of adjustment at the same time if all 4 plugs are sooty.

Stan, its a single carb car so air cleaner is a good call although I fitted a new one before selling the car to Andy and its not done many miles since. I suspect the float valve (new as well) or float may be to high.

The other symptom is that the car dies (or almost dies) at a junction .......

[Jaydub]

As you know Tim, it would stall and idle badly if too rich. The float level on that carburettor is determined by the aluminium washer under the needle valve, therefore if the correct washer for that car is fitted the level should be correct. Washers are available in varying thicknesses of 0.5 mm increments.
Another thing to check would be the fuel pressure, which needs to be less than 2.5 psi.

[peterbaker]

My 28/36 on the Flavia was suffering from a worn spindle, I changed the carb with an unworn unit and bingo, super tick-over and much easier to set mixture.

[lancialulu]

As you know Tim, it would stall and idle badly if too rich. The float level on that carburettor is determined by the aluminium washer under the needle valve, therefore if the correct washer for that car is fitted the level should be correct. Washers are available in varying thicknesses of 0.5 mm increments.
Another thing to check would be the fuel pressure, which needs to be less than 2.5 psi.

John any idea what the correct thickness washer is?

[Jaydub]

Hi Tim,
No I don`t know the washer thickness from memory, but if adjustment fails to fix the richness and flooding is suspected I would remove the needle valve, measure the washer thickness and obtain one 0.5mm thicker.
I believe there is a spring loaded ball type needle valve available to stop vibrational flooding, and this would, by design, lower the fuel level slightly.
Geoff at Gower & Lee is the man to speak to on service parts. Tel. 01923 247300.

[Angle Grinder]

Not helping the debate much, but when I told my Professional mechanic friend that my car was running too rich he asked if the car was starting, idling and driving OK. I said "Yeah, it runs perfect, better than my wife's Toyota". To which he replied "So don't change anything".

[the.cern]

My real concern here is that I am getting too much fuel into the cylinders and 'washing' the oil film from the cylinder bores!!!

                                      Andy

[Angle Grinder]

I've also got sooty plugs on my 1967 1.8 Flavia, running on a single Solex carb that was fitted new in 1999. The car drives great, starts on the button hot or cold and has no misfires or hesitation. A little bit of popping on the fast over-run, but that's all.

I was running the car for ~4K miles on the slightly hotter NGK BP6 spec plugs. All the plugs were sooty, but Cylinders 1 + 2 were noticeably sootier than 3 + 4.

2 weeks ago, I fitted new plugs of the correct lower temp NGK BP7 spec and did a run of ~30 miles with a mix of motorway 70 mph cruising and spirited back lane driving. When I removed the new plugs the front ones were already sooted on the insulator. The rear plugs were a bit sooty, but within tolerances.

I run the car with a Malpassi Super King fuel filter and pressure regulator. I checked the fuel pressure which was just a shade over 2 psi. I've now lowered this to ~1.75 psi.
WHAT IS THE CORRECT FUEL PRESSURE FOR A SOLEX CARB?

After a ~20 mile run, the front plugs have light grey electrodes, but the insulator is still all sooty. The rear plugs are clean with no soot on the insulator at all and light grey on the electrodes.

The curious thing with the No.1 cylinder plug is that it only has soot on one face of the insulator, i.e. it looks like it has been spray painted from one side only. Could this be a symptom of a sticky valve?

Is it common for the Flavia engine to have sootier front plugs due to the front cylinders running a bit colder in the slipstream of air entering the engine?  Maybe I just need to do a much longer run to get a more even temperature through the engine.

[lancialulu]

I think you may be be benefitting by lowering the fuel pressure although the Solex/dellorto/weber spec is c3psi.

To do a proper plug chop you need a hot fast run and stop immediately and whip the plugs out. If you can get the engine up to operating temp and find a road to run at 70mph for 10 plus miles then stop that will give a more accurate indication of general running.

For what it is worth my Flavia inezione has nice brown/tan plugs on such a test running the ngk bp7es.