Lotus Elan

My (new to me) car is a bust. Nothing works.

PostPost by: miked » Tue Feb 02, 2021 6:14 pm

I have run Zenith Strombergs with fixed needles and adjustable ones. The top ajustable ones only do 3 turns anyway. Set in the middle they do 1.5 turns up and 1.5 down and actually unscrew if you go beyond the 3 turns. As i recall the fixed ones were marginally adjustable on how they sit in the slide. I remember the manual showing a ruler put across the bottom onto the edge on the spring biased needle.
All this of course is irrelevant if the brass jet that the needle moves within is set wrong.
I recall 96 thou being the start point. Also these jets are an interference fit and require a flat punch to move them within the body. Carb guys have a tool that srews in the bottom that pushes the jet in via turning a tommy bar.
I would look at setting them there and then colour tune check the combustion flame to see how near you are.
I have an old thread on here about "dirty bottom" as my white rear end got mucky with rich mixture. Brass jets were too low set by a so called carb guy that did not know.
Mike

Elan S4 Zetec
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BMW rninet scrambler
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PostPost by: andyelan » Tue Feb 02, 2021 6:54 pm

Hi there

Just an obvious one re the electrics but presumably you've checked the fuses are ok

Andy
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PostPost by: nwbaxter66 » Tue Feb 02, 2021 6:58 pm

Mike
I am also in Nebraska with a plus 2.
I am not going to curse myself by commenting on my electrical system, but have a relatively competent set of hands to offer assistance.
I have webers so not much help on the carb front, but I have lots of books, diagrams and parts (:
N
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1969 Plus 2 (UK) - sold
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PostPost by: SENC » Wed Feb 03, 2021 12:24 am

Mike - I'm attaching a Lotus Service Bulletin on the topic of jet height. Yours appears to be too shallow by .42mm. I'm not saying that is your problem, but as you may have ascertained from miked's post about adjustable needles, the adjustment window is pretty narrow. So, it is possible you're in a range that will run at idle but not as the pistons open. In theory, assuming no real needle or jet wear, at that depth you should be lean. A possible quick test would be to open the choke very slightly to see if that richens things enough that you can use the throttle at all.

Re the temperature compensator and bypass, many recommend just shutting them. I rehabbed my temp compensator, but blanked off the bypass valve altogether. I'd make sure both are in the shut position for now just to take them out of the equation while you're hunting for problems.

As someone else alluded to, vacuum is critical. Assuming the carbs are mounted properly and no air leaks around them, I'd definitely double check the vacuum take-off to the lights and dizzy vacuum advance if your car has one. I'd think this would be a notable issue at idle, too, but worth checking anyway.

As you replace the fuel filter, I'd pull the fuel line off the carbs and run it into a jar and just see how the flow is. Won't tell you pressure, but will at least make sure fuel is getting that far with enough flow to keep up.

I wouldn't worry with adjustable needles right now, get things working first, but if you decide to go that route later you can find the pistons for them. I'll search my notes if you look for them and cannot find them.

Last, take some pictures of things and post. There are so many knowledgeable people here, someone will pick up on something that will help, I can assure you. Pull the pistons and take a picture of the needle as it sits in the piston from a few angles, take some pictures of the needle in the jet from the throat, etc., etc.

Henry
LSB-StrombergJetHeight1.jpg and

LSB-StrombergJetHeight2.jpg and

LSB-StrombergJetHeight3.jpg and
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