Soled carbs

[Spider2]

I am sure this subject has been discussed many times but I cannot find the answer to my specific (possible) problem.
My series 1 1.3s has always lacked power above 5,000 rpm unless the ignition is advanced so much it pinks. I assumed it was a timing problem but now I think it is carburation.
I can get the car to idle beautifully by adjusting the idle mixture screws (and all 4 perform correctly). The carbs are well balanced but when I take it for a spirited test drive and examine the spark plugs the front 2 are very sooty whilst the rear 2 a perfect colour. Weakening the front carbs makes it run rough so it is only running rich at higher throttle/rpm.
I am guessing this could be float level too high or maybe blocked air jet on the main jets or even the idle jets?
Am I correct in thinking the two upper jets are the idle and accelerator jets and the main jet is underneath?
Anyone had a similar problem?
Thanks
Simon

[dhla40]

If you take off the small cover on the top the two large jets are the air correctors, remove these and make sure the emulsion tube is attached to them on the early carbs the tube has a small brass plug in the bottom on the later ones the tube is open, make sure yours are all the same. On the top of the jet it should be marked 180 but the hole size will be 1.65mm, check this with a drill bit to make sure they are not blocked. Finally get a small torch and look down the tube wells to compare the fuel levels, check this with a bit of wire bent at right angle to rest on the edge of the well and cut to 19mm for early carb or  22mm for later carb with brass insert at top of well. Main jets are not accessible from top of carb.

Sean

[lancialulu]

The other jet to the side of the large one is the idle jet with its own mini emulsion tube which controls the progression on to main jet operation. Power flattening off above 5000 could be also due to incorrect valve timing/cam wear and or tappet setting or inefficient exhaust system... Sooty plugs indicates rich mixture. Could be a problem on the main jet circuit of the front carb. Easiest way to check float chamber level is to withdraw an emulsion tube and use a small black cable tie as the fuel will fill the grooves up to  the level. Mark a datum with white or something which is were you place the tie at the top of the casting the emulsion tube sits in. Should be 19mm. Adjust by carefully bending the fuel float chamber floats. You will need to take the top off.

[Spider2]

Thanks, will do some investigation and report back.