Rough running and back firing problems. Help needed

[juicerider]

Well I just got my S2 on the road after very little use by the last owner.
I've done about 300 miles n it and its been running very rich. The plugs are covered in soot after just a quick trip round the bloc. It has Weber carbs and occasionally used to spit back through the carbs.
I checked the jets in the webers and they are as the Haynes manual recomend, the only thing that I changed was the float level which was set too high. I adjusted the idle mixture and balanced the carbs.
Next time I ran it the car has a huge flat spot just above idle and backfires like crazy into the carbs.
After much tinkering the car now backfires into the exhaust as well. I can set the idle up and it will be backfiring out of both ends at once now, and from all 3 carbs
Today I took the distributor apart as I found the fly weights were not working correctly and reset the ignition timing to 10deg BTDC at 1000rpm.
Again to my disappointment this also made no difference.
Is there anything else I could try before I rip the head off to check for damage or stuck valves?
Thanks
Steve

[christopher storey]

I'm afraid that Weber settings are far more complicated than can be dealt with by the haynes manual. In the first place, many sets of DCOE have main venturi which are far too big e,g, 40 rather than say 38, 36 or even 34, and if this is the case you will never get a proper setup because whatever you do, the engine will be overchoked . The next most crucial component is the emulsion tubes which govern progression from idle to main jets . Get the wrong ones and the car will be an absolute dog except on full throttle . Generally speaking , the bigger the main venturi, the more sensitive to emulsion tube the engine will be . From memory most standard E types will run well with F9 or F16 but don't take this as gospel ( and I think one or two people on this board have had success with F2 . The other thing that happens is a functional one in that either people do up the spring washers hard and tight, and the carbs then froth and misbehave in all sorts of ways, or else they are not tight enough, leading to air leaks and then ( as may have happened in your case ) the rubber O rings get blown out by backfires and the mixture goes away to blazes ( no pun intended but I have had a fire this way!)

The best thing I can advise is to buy the John Passini booklets which are in my view far and away the best guides to Webers which there are. I feel certain that S/H copies will still be available even if they are out of print

[Heuer]

We have these guides in the Forum Knowledge Base:
Weber Set up Guide 1: http://dl.dropbox.com/u/8496016/Weber%2045DCOE.pdf
Weber Set up Guide 2: http://dl.dropbox.com/u/8496016/Weber%20Wisdom.pdf
Tuning DCOE Carburettors by Kimble & Trindal: http://dl.dropbox.com/u/8496016/Tuning% ... uretor.pdf

Time consuming and expensive to get them right. I think the biggest problem is that in period 40mm DCOE were used but now only 45mm DCOE seem to be available.

[juicerider]

Thanks for the advice
Christopher the emulsifier jets are F2 on the mains and F8 on the idle.
The coke is 38mm
I removed the carbs today to check the o ring you mentioned and mine has not got one, it has a fiber spacer. I could not see any evidence of a leak here either, which is a shame as I'm running out of options.
Do you think re seating the valves would help?

[abowie]

To be honest, the only way to tune Webers properly for any aftermarket indication is to find an expert tuner with a dyno and get them to set the carbs up properly for you. The o rings act to stop vibration messing with the fuel in the float chamber, but that isn't going to be your main problem.

[christopher storey]

It is the emulsion tubes themselves that are important . These are the tubes about 40mm long with holes in the circumference , and which carry the jets "plugged in" at the top and bottom ends. It sounds as though yours may be F2 because main jets and/or the air correctors usually do not have such a description , being sized only eg 150 or 175. The idle jets do have an alphanumeric designator but it is usually something like 60 F8, so maybe that is what you have . Those fibre spacers do not look suitable for Webers to me - the flexible mounting is essential , and your carburetters should have an annular recess on the face which meets the manifold which is there to accommodate the O rings. Mind you, I agree with Andrew that there are more troubles than just fuel frothing at work here. Has it ever run properly ? If not, valve timing ? Or ignition timing - be warned that the pointer , particularly if it is on the side rather than the bottom of the front cover, can often be bent or moved so that it gives a false indication

It is best to check the true position of TDC with a dial gauge in front or rear cylinders - another warning - the pulley can partially delaminate so that the outer part which has the timing marks slides round on the inner and is another means of giving false timing marks

[dal2.0litrefrogeye]

Hi . Between the face of the carb and the manifold should be 2 o ring that sits either side a nylon plastic holde,r or the bonded type which are called misab washers/ plates which are alot more reliable . And a good rolling road session is your friend . Do persavear with them because once set up right there is little to go wrong and the performance well and sound lovely