Lotus Elan

Rear cylinders not firing/misfiring

PostPost by: twincamman » Mon Oct 14, 2013 11:21 pm

Now. Ease off on turning the. Balance. Screws you may want the screw just to be free of touching the front carb tang the rear carb needs actuate a shade before the front ....try that ....sounds like you are screwing it in too far oiiii....that should get me banned again
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PostPost by: billwill » Wed Oct 16, 2013 1:48 am

I use a Colortune transparent spark plug to set the idle mixture. You can't beat being actually able to SEE the colour of the flame.

And you can be absolutely sure that it is firing.

Defininitely worth the money and lasts for ever.
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PostPost by: Fuzzy748 » Wed Feb 26, 2020 5:56 pm

Hi Timok, did you resolve the issue with the two rear cylinders (3&4) as I have the identical problem, equal good compression on all cylinders, good spark on all plugs, electronic ignition just installed, both floats set the same height, fuel present at same level in both carbs when floats removed, carbs just serviced, correct firing order, etc
I can take both rear plug leads off and it makes no difference, the engine starts and runs lumpy obviously as on two front cylinders but run it does !, I’ve tried easy start on both rear chokes but no difference, the only thing I haven’t done is swop the carbs front to back which’s my next step, any suggestions most welcome
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PostPost by: mbell » Thu Feb 27, 2020 7:32 am

Have you checked the firing order on 3 & 4?

Has the engine ever run on all four? If so what have you done since then?
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PostPost by: Fuzzy748 » Thu Feb 27, 2020 3:46 pm

Hi, yes firing order/plug caps correct, I haven’t had it running previously as I bought it as a complete car that had been stored for some time, what I don’t understand is just how well it runs without 3&4 plug caps connected, I thought it wouldn’t run at all,
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PostPost by: Craven » Thu Feb 27, 2020 4:08 pm

Check out carb synchronization, if you don’t have any equipment for this, with air box removed a suitable length of hose pipe the larger dia the better and listen for equal hiss at each trumpet.
Balance between carbs is adjusted by spring loaded screw between carb on spindle. On pic above throttle cable.
[attachment=0]SPRING ON CABLE.JPG
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PostPost by: alan.barker » Thu Feb 27, 2020 4:40 pm

I'm no mechanic, and I have little to no experience with carburetted engines. Any help is greatly appreciated!

-Timo
Imho Timo you would be better to contact a classic car garage and get them to set it up :wink: :wink:
Quicker and easier as you said you're no mechanic.
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PostPost by: promotor » Thu Feb 27, 2020 4:59 pm

Have you tried spark plugs 3 & 4 in cylinders 1 & 2 and vice versa? Compression can do funny things to plugs that may seem ok in free air.

Are the venturis in the carbs fitted the correct way?
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PostPost by: Concrete-crusher » Thu Feb 27, 2020 7:11 pm

If you got hold of a gunsons color tune you could see the 2 cylinders firing, and set the idle mixture.

Just a suggestion
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