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Re: [Healeys] advice needed -- BT7 electric choke problem

To: britfan1@epix.net
Subject: Re: [Healeys] advice needed -- BT7 electric choke problem
From: Michael Salter <michaelsalter@gmail.com>
Date: Thu, 18 Dec 2014 16:51:24 -0500
Cc: Healey list <healeys@autox.team.net>
Delivered-to: mharc@autox.team.net
Delivered-to: healeys@autox.team.net
References: <AA2AE9DB18DF40078CAECD149C6E9982@HomePC>
Hi Sarah,
With the auxiliary carburetor (electric choke) right out of the equation
(turned off) the carburetors are the same as any other HD type. I presume
that he has confirmed that there is no air flow through the auxiliary
carburetor when it is not activated and that there is no other source of
air leakage into the inlet manifold such as the fuel drain tubes on the
underside of the manifold being missing or a leaking inlet gasket.
Most important is to ensure that the butterflys are fully closed. To check
this properly the link joining the throttle shafts between the carburetors
must be disconnected.
If the butterfly plates themselves are not accurately centered and secured
to the throttle shaft they will always leak air and it will be impossible
to to get the air flow past it/them small enough for the idle bypass screws
to be effective.
With the shafts disconnected an air flow meter can be used to determine if
one carburetor is flowing more than the other.
If the butterflys are closing correctly and there are no other air leaks
into the inlet ports the engine will stop if the idle bypass screws are
turned right down (closed).
Once that problem is it should idle with those bypass screws turned out
about 2 1/4 turns.
Michael S
BN1 #174



On Thu, Dec 18, 2014 at 4:21 PM, <britfan1@epix.net> wrote:
>
> A mechanic friend is trying to get the electric choke on a customerb s BT7
> (not a tricarb) to work satisfactorily.  He did have to install a dash
> switch
> wired to it in order to get it to turn on/off properly.  (Heb s familiar
> with
> this choke from previous experience with Jaguar engines, and he does have a
> copy of the 100/6b 3000 factory service manual.)  As I understand his
> description of the problem, heb s been able to get both carbs synchronized
> properly, and the car starts and idles well when warm.  However, turning
> the
> screw that regulates the amount of air that bypasses the throttle plates
> has
> no effect whatever on engine speed or exhaust appearance (richer/leaner
> mixture).  Suggestions, anybody?  [Apologies if this might not be perfectly
> clearb  I havenb t been to his shop to observe, only working from phone
> description and the photo in the 3000 ownerb s handbook.]
>
> Thanks in advance,
> Sarah Carr
> BN1 in PA
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-- 
*If you can't fix it with a hammer, you've got an electrical problem.*
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