Lotus Elan

Looking at my Dellorto's............

PostPost by: mark030358 » Tue Jul 19, 2005 7:53 am

Hi there,
Still trying to find my problem with regards to poor drivability at low rpms in top. Anyway, No4 mixture screw is only3/4 turn open while all the others are more. Plug is black and sooty after a run while the others are (sorry Keith, but a nice brown colour).

Had the carbs off and checked the butterflies for mal adjustment but the measurements I took showed no significant difference ie a 2 thou feeler gauge just passed each butterfly in the closed position.

So, looking at the carb the only place fuel could come from is the choke or starter valve to be more precise. When I completley rebuilt the carbs the rubber seal for the started valve was not included so the 32+ year old one is still in there. Anybody have problems with these and is it possible that I could bleed fuel into one barrel, bearing in mind the choke circuits are segregated at the valve by a mtal strip across the top of the chamber.

any help appreciated
Cheers Mark
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PostPost by: bill308 » Thu Jul 21, 2005 12:59 am


It's possible you are too lean on #4 and are getting a misfire/incomplete combustion under idle/near idle conditions. This could cause the plug to show soot rather than the expected whitish deposite. Also, if you don't have enough air flow to this cylinder (at idle), you will not be able to set a good mixture.

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