---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Tue 01/31/12: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:03 AM - Re: 912 80 hp back-fire on shutdown (Roger Lee) 2. 06:36 AM - Re: 912 80 hp back-fire on shutdown (ejessee) 3. 07:48 AM - Re: Re: 912 80 hp back-fire on shutdown (Lanny Fetterman) 4. 07:25 PM - Re: 912 80 hp back-fire on shutdown (dashwood) ________________________________ Message 1 _____________________________________ Time: 06:03:51 AM PST US Subject: RotaxEngines-List: Re: 912 80 hp back-fire on shutdown From: "Roger Lee" Here are a few things to check and try. First the header wrap isn't causing the problem. You are running a little rich and this could be caused by your shut down procedures. Is the air mixture screw on the bottom turned out only 1.5 turns? This needs to be double checked before the next test. Are you venting any fuel out the vent tubes? Slow the engine down to 1650-1750 before shutdown and turn one mag off for 2 seconds and then the last one. The 2100 rpm shut down may be part of the problem. Open the gap a little on the plugs to .025 -.026. (not my first consideration) .023 -.027 is the normal gap, but sometimes having a small gap gives an incomplete burn. You just may have more than one thing adding to your problem. If the above suggestions don't help then you may need to pull the carbs back off. This is what changed since the problem started and someone may have done something wrong on the carb rebuild. It could be something as simple as the float arm at the wrong height. My bet is it will end up being a carb issue. Have you done a compression leak down test? (This would be my last thing to do, but would remain in the back of my mind). -------- Roger Lee Tucson, Az. Light Sport Repairman - Maintenance Rated Rotax Repair Center - Heavy Maint. Rated Home 520-574-1080 TRY HOME FIRST Cell 520-349-7056 Read this topic online here: http://forums.matronics.com/viewtopic.php?p=365296#365296 ________________________________ Message 2 _____________________________________ Time: 06:36:32 AM PST US Subject: RotaxEngines-List: Re: 912 80 hp back-fire on shutdown From: "ejessee" Thanks to everyone for replies. As to the problem starting after the carb rebuild... it didn't start then. It has been happening for some time. I will check all the things suggested. I have been shutting down at about 2100. I will begin shutting down at 1700-1800 RPM. I already do the 2 second per mag thing at shutdown. I will be doing a compression check as my conditional is coming up. I just changed the plug gap about 2 months ago to ease in cold starting. the regap helped in cold start, but again... the backfire/after fire was happening before that change. I have checked the exhaust stacks... they are tight. There is no rust on the exhaust, so small leaks are unlikely... but possible. I'll check that as well. Thanks again to everyone. -------- Ernest Jessee N4931M Read this topic online here: http://forums.matronics.com/viewtopic.php?p=365298#365298 ________________________________ Message 3 _____________________________________ Time: 07:48:34 AM PST US From: Lanny Fetterman Subject: Re: RotaxEngines-List: Re: 912 80 hp back-fire on shutdown I joined this thread late, so maybe you already discussed this, also I have NO experience with the 912. However, aren`t backfires and ignition timing related? I fly a Kolb Firestar II Rotax 503. Lanny At 09:34 AM 1/31/2012, you wrote: > >Thanks to everyone for replies. > >As to the problem starting after the carb rebuild... it didn't start >then. It has been happening for some time. I will check all the >things suggested. I have been shutting down at about 2100. I will >begin shutting down at 1700-1800 RPM. I already do the 2 second per >mag thing at shutdown. I will be doing a compression check as my >conditional is coming up. > >I just changed the plug gap about 2 months ago to ease in cold >starting. the regap helped in cold start, but again... the >backfire/after fire was happening before that change. > >I have checked the exhaust stacks... they are tight. There is no >rust on the exhaust, so small leaks are unlikely... but >possible. I'll check that as well. > >Thanks again to everyone. > >-------- >Ernest Jessee >N4931M > > >Read this topic online here: > >http://forums.matronics.com/viewtopic.php?p=365298#365298 > > ________________________________ Message 4 _____________________________________ Time: 07:25:11 PM PST US Subject: RotaxEngines-List: Re: 912 80 hp back-fire on shutdown From: "dashwood" i would also put much weight into Mr Lee's comments, thanks for jumpin in as always... its hard to sit by and see someone misdirected. :) thanks -------- Ross Aalexander: CH701 driver 912ul 589tt It only takes two things to fly, airspeed and money Read this topic online here: http://forums.matronics.com/viewtopic.php?p=365351#365351 ------------------------------------------------------------------------------------- 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.