---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Sat 01/28/12: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 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) ________________________________ Message 1 _____________________________________ Time: 03:01:09 PM PST US Subject: RotaxEngines-List: 912 80 hp back-fire on shutdown From: "ejessee" 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 _____________________________________ Time: 09:37:11 PM PST US Subject: Re: RotaxEngines-List: 912 80 hp back-fire on shutdown From: Richard Girard 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 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 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rotaxengines-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RotaxEngines-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/rotaxengines-list Browse Digests http://www.matronics.com/digest/rotaxengines-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.