I am setting the float height on my webbers and i can follow the book fine and that gives me all the values i need but it does not seem to expain why they have to be so accurately set. I know it is something to do with the level the fuel comes to on the emulsion tube but can someone explain this for me?

I'm sure there are many people out there who know

Thanks . I hate doing things and no knowing how it works or why i am doing it - it's the scientist in me

Sounds like you answered your own question

The height of the fuel in the fuel bowl determines how high the fuel comes up the emulsion tubes, therefore determining how many holes on the emulsion tubes are covered and how many are not. Different emulsion tubes (lean to rich) have the holes at different heights on the tube, and holes of different sizes. Now obviously the amount of holes submerged varies as the fuel height in the float bowl varies under power, hence why you have a min and max setting for the floats and why its important to have enough fuel volume to stop the fuel level dropping too much so you end up with a weak mixture through the mains.

Just dont ask me to remember what order (lean to rich) the emulsion tubes go in, its not as easy as number order!

Heres a pinched bit of info:

F7......... For mixture enrichment at low rpm or during slight accelerations ( no orifices at the top)

F2, F11, F15, F16............ For mixture weakening at low rpm or during slight accelerations (orifices at the top)

F11....... For high rpm mixture richness reduction when air jet is larger than 2.00mm (many orifices)

F2,F3,F4,F7...... For very large main fuel jets or alcohol based fuels.

Interestingly a 2l pinto will run equally as well on F16 as it will on F2 emulsion tubes.

David

[Edited on 14/5/07 by flak monkey]

my tubes only have a ring of holes at the top. does this mean that as long as the fuel is covering these holes i am ok?

Also - i am assuming then that the lower stop on the float is only there to stop the centre of the fuel inlet valve dropping out and would not have any effect on fueling (unless it were too high)

ah yes mine are F16s i think

Its not as simple as that.

The F16s have a row of holes around the top, which gives a slightly weaker mixture as they can suck air in through those holes as well as through the air correctors in the top.

I wouldnt worry too much about it. DCOEs are bloody complicated. You know the rough jist of it now

You wouldnt want to buy a new set anyway, they are the best part of £70 for a set of 4 emulsion tubes. F16's will be perfect.

David