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1. 03:01 PM - 912 80 hp back-fire on shutdown (ejessee)
2. 09:37 PM - Re: 912 80 hp back-fire on shutdown (Richard Girard)
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| Subject: | 912 80 hp back-fire on shutdown |
Hello all,
I did a search in the forum with "backfire", "back-fire", and "back fire" with
no results, So here goes....
I have an 80 hp 912 UL on a Zenith 701. When I return to my hangar after flight,
unless I do a 2 -3 minute stabilization run at 2100 RPM, my 912 backfires like
a shotgun when I turn it off. I have newly rebuilt carbs, perfectly balanced
carbs, plugs at .024. The engine runs perfect, uses no oil. My exhaust stacks
are heat-wrapped. As severely as it backfires, I am afraid I am going to
damage my exhaust system.
Anyone else ever experience this? Anybody know what is causing it. Is something
wrong or is this just the nature of the engine.
AS always, thanks for your help. This forum is a fantastic resource.
--------
Ernest Jessee
N4931M
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=365064#365064
Message 2
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| Subject: | Re: 912 80 hp back-fire on shutdown |
There are two distinct and opposing conditions that could cause your engine
to backfire. Too rich an idle mixture letting unburned fuel slip by the
valves into an exhaust system already heated by high EGT's when the power
is pulled back on approach. Or the mixture is too lean and it's on the
verge of running on after the ignition is shut off.(my Harley used to do
this on warm up when I pulled the choke off too early).
What is your idle RPM before the stabilization run? Is it different after
the stabilization run?
If your heart can stand the strain, let it backfire one last time and
immediately look at the plugs. Do the same after a stabilization run and
note if there's any difference.
Rick Girard
On Sat, Jan 28, 2012 at 4:58 PM, ejessee <eejessee@us.ibm.com> wrote:
>
> Hello all,
> I did a search in the forum with "backfire", "back-fire", and "back fire"
> with no results, So here goes....
>
> I have an 80 hp 912 UL on a Zenith 701. When I return to my hangar after
> flight, unless I do a 2 -3 minute stabilization run at 2100 RPM, my 912
> backfires like a shotgun when I turn it off. I have newly rebuilt carbs,
> perfectly balanced carbs, plugs at .024. The engine runs perfect, uses no
> oil. My exhaust stacks are heat-wrapped. As severely as it backfires, I
> am afraid I am going to damage my exhaust system.
>
> Anyone else ever experience this? Anybody know what is causing it. Is
> something wrong or is this just the nature of the engine.
>
> AS always, thanks for your help. This forum is a fantastic resource.
>
> --------
> Ernest Jessee
> N4931M
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=365064#365064
>
>
--
Zulu Delta
Mk IIIC
Thanks, Homer GBYM
It isn't necessary to have relatives in Kansas City in order to be unhappy.
- Groucho Marx
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