Lotus Elan and Lotus Elan Plus 2 Forums

Can anyone give me a dimension from the rim of the jet cover to the correct fuel level on the above carbs?

I tried Webcons Technical Dept, but the only figure they gave was 12mm cover to float.

I think I can set the fuel level more accurately by direct measurement using Vernier Calipers, and a torch.

Thanks in anticipation

Dave

25mm is mentioned in this thread:
elan-mods-f31/hypojets-and-tubes-the-way-t25922-15.html

Brian,
thank you for your prompt response!

Dave

Dave,
I set the fuel level from above as recommended by Keith Franck of `side draft central` who knows a lot about Weber carburettors. he recommends 25mm below the top of the float chamber.

On my 151s the rim of the jet cover is 16mm above the float chamber top so I measure 41mm down from there.
I remove one of the main jets and use an ordinary vernier depth gauge and a small torch. When the tip touches the fuel the surface `shivers`. A cocktail stick or similar with a mark on it would work just as well.
The tolerance according to Keith is plus or minus 1mm.
This is critical because there is an orifice in the side of the chamber 2mm above the surface of the fuel, so you can see that an error of more than 1mm is significant.
Hope this helps
Eric in Burnley
1967 S3SE DHC

Thanks Eric,
Just got the covers off, and measured from centre of float to covers at 13mm on both.

But I can clearly see the fuel level in the front carb is higher than the rear.....by 3mm.

No 1 and 2 plugs are sooting up which is why the query originated.

John Clegg told me several times to check the fuel levels, before it sank in!

Going to fit new needle valves before I finish as slight ridging on them.

Dave

I made myself a little tool to help with checking/setting. It's a simple bit of metal coat hanger with two 90 bends to make a kind of flat Z shape. This has one prong that is 25mm and one that is 26mm (I formed the shape then cut/filed to length) with a little ledge that can be sat on the edge of the jet holder.

The main advantage of this is that it is very compact so relatively easy to see down the jet holder with it inserted. You can also angle it slightly to make it shorter/long than the desired level to see if your just over/under the desired level.

Thanks for your replies Gents
I'm quite happy that the depth gauge on my Vernier calipers is easy to use, and gives accurate readings.

I'm waiting for the new needle valves before I put the covers back on and set the levels.

But it does seem to me, that if I set the fuel level to 41mm as Eric says, the float to cover gap will be significantly more than the 12mm as given by Webcon?

Also, Webcon didn't give me a dim for the fully open position of the floats, but I suppose that isn't as critical.

Dave

General guidance from Weber Tuning manual.
Check the float maximum lowering position; the needle must travel a distance equivalent to slightly more than the diameter value ( in mm ) stamped on its seat.
The fuel height in the bowl must be kept at a lower level with respect to the spray nozzle bore. Level may be set at a height of less than 5 ? 6mm below the bottom edge.
Data sheet for 151 12mm + - 0.25. with gasket.

I found that the acrylic rod method described by Keith Frank was easier than the vernier gauge as it?s very easy to see when the rod touches the fuel once you have had a bit of practice. The level should only be checked within a few minutes of the engine running to ensure you get the genuine level.
Ed

Hi All

This may be of interest.






It can be measured with jets out engine running

Thanks for the most recent posts. Got the new needle valves yesterday.
Floats gapped at 12mm with the gaskets in place.

I ran the engine for a few minutes, then immediately checked the fuel levels.

I found, that with both main emulsion tubes removed, I could check the fuel level from the top of the carb body, using my verniers quite readily.

Should be 25mm.
Reading 30 mm on all 4 chambers.

Any thoughts before I start adjusting the floats?

Thanks
Dave

Hi Dave,
My only thoughts are that it does need to be 25mm, and that as each carburettor has only one float chamber, then only one measurement is needed.
Each miilimetre of adjustment on the float gives 1mm adjustment on the fuel level, but maybe that is too obvious.
It does seem a big difference. Try my 41m measurement from the jet cover rim to see if we are measuring from the same place.
Keep going.
Eric in Burnley

Eric,
with my best reading glasses on:-

Fuel levels are

31mm from top of carb body
47mm from rim of jet cover.

Will fiddle with the floats tomorrow.

Dave

Be sure to adjust the pivot of the float side to side. Takes a bit of time, but must be done before you set the fuel levels.

I tried bending the tabs to raise the fuel level, but it only seems to slightly alter the level.

Bending the actual float arms might do it?

Or using a thinner washer under the needle valve......I've got a thick steel washer, which does seem the right one ,looking at Eurocarbs exploded drawing (1.2mm thick)

Sorry, but I don't understand how I can adjust the pivot of the float side to side?
Its just a simple pin which locates in the 2 shoulders under the cover.