Re: [AMC-List] backfire through carb

["Jim Blair" <carnuck@xxxxxxxxxxx>]

A: A Duraspark box on it's way out can cause backfiring as well. I kept a 
spare in mine (still have several around. Won't be needing them anymore as 
my J4000 is points and the others are all Renix or HO EFI)


From: Tom Jennings <tomj@xxxxxxx>
Subject: Re: [AMC-List] backfire through carb
To: amc-list@xxxxxxxxxxxx
Message-ID: <1150920558.6260.11.camel@xxxxxxxxxxxxx>
Content-Type: text/plain

On Wed, 2006-06-21 at 08:28 -0700, Jim Blair wrote:
>Too retarded is more likely to cause backfire under those
conditions. Also
>vacuum leak, weak spark, too lean, cam walk are also in the
running. Then
>there is sticking valves ( a bit of Marvel Mystery oil in the
tank helps
>that!) and vacuum advance with a hole in it. If you're running
points, the
>dist internal ground could be seperating, points getting too
much
>resistance, and a whole lot of other things. (I could tell
what it was if I
>could hear/see it in person)

Thanks for the tips. I'll start diagnosing this weekend (sigh, I
have
other things to do).

I've got a Duraspark II, I'll check distro and timing and
eliminate all
that. Engine should be like-new (20K mi), so sticky valves seems
unlikely, it's lived on synth oil changed religiously.

I have it pretty lean, so that's a candidate; I'll re-check the
squirter
for stroke and leaks (I had a bad squirt pump diaphragm last
year). It
does seem to happen only when the secondary is open, so I can
rich that
up a jet size or two or three (it never cruises with secondary
open;
it's really easy to feel in the pedal).

I hope it's ignition or sec main jet cuz it's easy to fix and
I'm lazy.

Thanks again!

tomj

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