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I dunno if it can cause high RPM backfiring (I think it could), but
the airflow on all (2-3) carbs has to be the same--or, at least,
very close--at all throttle positions. This has to be checked
off-idle, obviously, but if it's good at, say, 2,500RPM it should be
good at all speeds; if not, you have to disconnect the throttle
connect shaft to set them. I suppose a crack Brit-car mechanic can
test with the recommended 'hose-in-the-ear' technique--my ear hose
is collecting dust somewhere--but I use a Uni-Syn.<br>
<br>
To paraphrase the TV commercial we've all (probably) seen a thousand
times: "If you don't have a carburettor synchronizer, get one."<br>
<br>
Bob<br>
<br>
<div class="moz-cite-prefix">On 1/29/2021 6:13 AM, healeyguy--- via
Healeys wrote:<br>
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cite="mid:1753560953.193599.1611929637112@mail.yahoo.com">
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<div style="color:black;font:10pt Arial, Helvetica,
sans-serif;">Len and Listers</div>
<div style="color:black;font:10pt Arial, Helvetica,
sans-serif;">Pushing the pin up to lift the piston is the
start of the "test the mixture setting" exercise. You
begin the push, ever so slightly, and listen to the
idling engine. The idle goes up. What do you do next? You
continue to raise the pin to see what happens. If the
idle continues to rise you know you are in a rich
condition. If the idle stops going up and starts to drop
off the mixture is pretty close. If the idle does not
increase from the start you usually assume you are in a
lean condition. This gets the carb mixture close at idle
which in theory means the carb is going to operate
throughout the RPM range. </div>
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<div style="color:black;font:10pt Arial, Helvetica,
sans-serif;">There is one other assumption here, that
being that the carbs is in the same condition as new
mounted on an engine operating as new. That is when allot
of other stuff comes into play. The carb float bowl
items, needle/seat and float level must be set correctly.
Float must not be leaking thus making it sink. Carb must
have the correct main needle and jet and they have to be
installed and adjusted correctly. <span style="font-size:
10pt; background-color: transparent;">Flutter at high
RPM may indicate that the piston spring in the suction
chamber is weak or the incorrect spring installed.
Ignition timing and condition and setting of ignition
points.</span></div>
<div style="color:black;font:10pt Arial, Helvetica,
sans-serif;">The list goes on and on......</div>
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<div style="font-family:arial,
helvetica;font-size:10pt;color:black;">-----Original
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From: Leonard Berkowitz <a class="moz-txt-link-rfc2396E" href="mailto:DrBerkowitz@hotmail.com"><DrBerkowitz@hotmail.com></a><br
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Subject: [Healeys] Another backfiring question<br
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Hi all</div>
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Just finished repairing and reinstalling the
carburetors on my BJ7. I thought I had
everything adjusted properly. According to my
Haynes Manuel the engine speed should increase
slightly when you lift the piston a very small
amount. Mine does that. My dwell angle is where
it needs to be and the car starts and idles
nicely. Also sounds beautiful when I punch the
accelerator linkages. The problem is that when I
get it up to 60-70 mph I get what sounds like
backfiring into my carburetors. Also sounds like
it doesn’t have a whole lot left in the tank, so
to speak. Does that sound like I am running too
rich or too lean? </div>
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Len Berkowitz </div>
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