Running too rich

[Wangler]

Please pardon my ignorance over what is I'm sure a basic question. I'm used to SU and Stromberg carburettors and never had to play with Solex or Weber.

Went out for a drive this morning in my S3 and where I could gave it quite a bit of wellie. The car ran very well but it seemed to use quite a lot of fuel (Esso Synergy Supreme+99 Unleaded), although I don't know what consumption I should expect.

Looked at the plugs (Champion N9YK) and they're all a bit black. Is there an easy way of making the mixture more lean, or is it a case of changing jets?

If it's the latter, what is the recommendation? Is it a simple swap?

[Jaydub]

make sure the choke is fully off against the stops, that will make it use more fuel. Did you check the plugs after driving slowly back to your house through traffic etc because that is not the way to check plug colour.
Find a straight stretch of road a few miles long and a layby you can pull into safely. Do a full throttle run, switch off the engine and pull into the layby and then check the plugs. MAKE SURE YOU DON`T LOCK THE STEERING WHEN YOU TURN OFF THE ENGINE!!

[Wangler]

Thank you. Choke fully home.  I haven’t gone so far as to stop the car immediately after a full throttle blast as you described, but TBH I’ve seen enough plugs to know if an engine is running rich. There was no idling in traffic just before the engine was stopped.

[lancialulu]

Fulvia set up is generally on the richer side. As John says a best check is a plug chop from full throttle run. Sooty plugs at tickover could just be fuel level in float chamber (s). Should be 19mm from top of emulsion tube when removed without taking the top cover off and after the engine has idled for a bit. A suitably size and marked cable tie is a cheap and quick way to check down the emulsion tube. Only jetting changes on Fulvia is upping the idle jet (to get better transition from idle to main carb circuits with modern lower s.g. fuels, and or upping the main jet is the engine has been tuned and is running the engine flat out (racing etc). In both these cases it is not going to be your situation. A sooty plug could be just burning oil too (valve guides main culprit).

[Richard Fridd]

Looking forward to the solution. Regarding fuel level, I like the suggested method of using an improvised  and calibrated dipstick, then  observing the point at which a surface tension 'wink' occurs. (from the other float level thread)


  Richard

[Spider2]

Webers and Solex's may appear complicated but they are basically very simple pieces of kit. The idle mixtures screws just do that, adjust idle mixture. Rest is set by the main jets/air correction/ and to a certain extent the emulsion tube. Start by checking idle mixture screws, they can be damaged if tightened down to much. Then check you have factory setting jets fitted (or close). Learn about these carbs and you will save yourself a fortune because getting bad carbs correct can take hours and hours of fiddling and adjusting. Omicron do a small booklet on the Solex carbs and reading it you will find out how little can actually be done. I prefer the Webers over Solex, mainly because the main jets on the Solex cannot be changed with the carb bolted to the car. (they are underneath)
Happy fiddling