Lotus Elan

Stuck Stromberg top

PostPost by: Pete M » Wed Jun 17, 2020 2:52 pm

I was hunting down the reason for the sudden development of a misfire at high speeds the other day and discovered that I could not remove the top on the front carb. I wanted to check the diaphragm. If I tap a corner, it will rotate slightly but I was reluctant to use any real force on it. Has anyone else encountered this? Solution?
By the way, after checking cap, rotor, plugs, wires and the diaphragm on the rear carb, I found loose nuts holding the front carb to the manifold. Hoping that solves the misfire. It's been rainy lately, haven't had a chance to test it.
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PostPost by: 69S4 » Wed Jun 17, 2020 3:11 pm

Not catching on the clip for the choke cable is it?
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PostPost by: RogerFrench » Wed Jun 17, 2020 3:25 pm

You do know that the nuts should not be tight? The carbs are flexibly mounted.

Occasionally the tops do stick, but if you can rotate it slightly, then persevere without using brute force.
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PostPost by: Pete M » Wed Jun 17, 2020 3:43 pm

I assume there should be no air gap between the carb mounting surface and the manifold, I watched it close as I tightened the nut.
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PostPost by: Pete M » Wed Jun 17, 2020 3:53 pm

No catch on the choke cable or bracket.
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PostPost by: SENC » Wed Jun 17, 2020 4:50 pm

Pete M wrote:I assume there should be no air gap between the carb mounting surface and the manifold, I watched it close as I tightened the nut.


Should be carb to adaptor plate with a gasket in between, then an o-ring between the adaptor plate and the manifold. The carb to adaptor plate is a tight/hard fit - adaptor plate to manifold a soft fit, with thackery washers (or the rubber compression variety) on the bolts. There should be a visible gap between the adaptor plate and manifold, but I don't remember the size. If using thackery washers, I think a 5 thou gap between "coils" is the right setting. The intent is to make the connection airtight, consistent all around, and flexible (to prevent fuel frothing from vibration).

Found the following thread with some comments and pictures that may be helpful...
viewtopic.php?f=15&t=19540&start=
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PostPost by: Pete M » Thu Jun 18, 2020 9:16 pm

A little more research into this has resulted in ordering new o*rings, thackery washers and nylock nuts. The gap
is supposed to be .070". Since the gap closed upon tightening, I have to assume the old o-rings are toast.
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