---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Wed 08/18/10: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:01 AM - 447 analysis (David Kulp) 2. 07:50 AM - Re: 447 analysis (lucien) 3. 04:38 PM - Re: 447 analysis (Richard Girard) ________________________________ Message 1 _____________________________________ Time: 07:01:55 AM PST US From: David Kulp Subject: RotaxEngines-List: 447 analysis A question for the experts. I have a 447 on a Kolb FireFly and have been unable to get the engine to settle in mid-range RPMs. If I have the throttle set at a certain point the engine runs strong at 5400Rs, but when I try to decrease the Rs to about 48-5000, the smallest reduction causes the engine to slow to about 4300. I pulled the plugs after landing yesterday and the front cylinder's plug is an even tan color, but the rear plug is the same tan on half of the electrode and ceramic cone and sooty black on the other half. First thing that comes to mind is a leaking head gasket, but also wonder if I should check the torque on the head bolts first, and has anyone ever heard of a spark plug "leak" - either the gasket or the plug itself? Further info that may or may not be pertinent, my CHT gauges show one cylinder in normal heat range and the other is rather chilly. Checking this out a while back I checked the temp of the plugs and the heads with a laser thermometer and they were withing a few degrees of each other, so I attributed the difference to the gauge or the thermocouple. But maybe it has something to do with the Blackie Carbon lurking on half my rear cylinder plug. Any thought from the experts on the list will be greatly appreciated. Dave Kulp Bethlehem, PA FireFly 11DMK ________________________________ Message 2 _____________________________________ Time: 07:50:33 AM PST US Subject: RotaxEngines-List: Re: 447 analysis From: "lucien" undoctor wrote: > A question for the experts. I have a 447 on a Kolb FireFly and have > been unable to get the engine to settle in mid-range RPMs. If I have > the throttle set at a certain point the engine runs strong at 5400Rs, > but when I try to decrease the Rs to about 48-5000, the smallest > reduction causes the engine to slow to about 4300. > > I pulled the plugs after landing yesterday and the front cylinder's plug > is an even tan color, but the rear plug is the same tan on half of the > electrode and ceramic cone and sooty black on the other half. First > thing that comes to mind is a leaking head gasket, but also wonder if I > should check the torque on the head bolts first, and has anyone ever > heard of a spark plug "leak" - either the gasket or the plug itself? > > Further info that may or may not be pertinent, my CHT gauges show one > cylinder in normal heat range and the other is rather chilly. Checking > this out a while back I checked the temp of the plugs and the heads with > a laser thermometer and they were withing a few degrees of each other, > so I attributed the difference to the gauge or the thermocouple. But > maybe it has something to do with the Blackie Carbon lurking on half my > rear cylinder plug. > > Any thought from the experts on the list will be greatly appreciated. > > Dave Kulp > Bethlehem, PA > > FireFly 11DMK Yeah, both of my 447's did this. My single carb 503 did it also tho to a lesser degree. I think it's just a property of the single carb configuration, but what the exact cause is I couldn't say. There's not a whole lot you can do about it, really. One thing that seemed to help on my engines was varying the load in the spot where it tended to wander. I.e. add a little pitch (or just fly slower) to load the engine a bit more. This will require opening the throttle a little more which may get it out of that wandering range (that worked on my old 447 equipped trike) and make it settle down. I also tried different needle settings on the theory that it was lean in that spot. Raising the needle one notch helped with the hair-trigger throttle on my trike's 447, but it also made it so rich it stumbled and burbled a little bit. That was more objectionable to me than the wandering so I set it back where it was. It sounds like your EGT's are actually a little cool in that range which could be either a little rich or too much load (or both). The really expensive option is to go with the dual-carb setup, if you can still get the little Bing carbs and manifolds for this. This will completely eliminate the problem (or at least it did on a friend of mine's Starlight/447), but it may be too pricey and difficult to make it worth it. I just learned to live with it myself, generally by just flying slower and loading the engine a little more when in that particular throttle range.... LS -------- LS Titan II SS Read this topic online here: http://forums.matronics.com/viewtopic.php?p=309284#309284 ________________________________ Message 3 _____________________________________ Time: 04:38:03 PM PST US Subject: Re: RotaxEngines-List: 447 analysis From: Richard Girard David, A little info please. Is this problem a sudden onset or did it happen gradually? Did the engine sit awhile in storage? Is there any crud in the carb float bowl. Have you checked the carb socket for cracks? How is your prop set? What RPM do you get static? What RPM do you get at WOT in straight and level flight? Rick Girard On Wed, Aug 18, 2010 at 9:00 AM, David Kulp wrote: > > A question for the experts. I have a 447 on a Kolb FireFly and have been > unable to get the engine to settle in mid-range RPMs. If I have the > throttle set at a certain point the engine runs strong at 5400Rs, but when I > try to decrease the Rs to about 48-5000, the smallest reduction causes the > engine to slow to about 4300. > > I pulled the plugs after landing yesterday and the front cylinder's plug is > an even tan color, but the rear plug is the same tan on half of the > electrode and ceramic cone and sooty black on the other half. First thing > that comes to mind is a leaking head gasket, but also wonder if I should > check the torque on the head bolts first, and has anyone ever heard of a > spark plug "leak" - either the gasket or the plug itself? > > Further info that may or may not be pertinent, my CHT gauges show one > cylinder in normal heat range and the other is rather chilly. Checking this > out a while back I checked the temp of the plugs and the heads with a laser > thermometer and they were withing a few degrees of each other, so I > attributed the difference to the gauge or the thermocouple. But maybe it > has something to do with the Blackie Carbon lurking on half my rear cylinder > plug. > > Any thought from the experts on the list will be greatly appreciated. > > Dave Kulp > Bethlehem, PA > > FireFly 11DMK > > -- Zulu Delta Mk IIIC 582 Gray head 4.00 C gearbox 3 blade WD Thanks, Homer GBYM ------------------------------------------------------------------------------------- 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.