---------------------------------------------------------- JabiruEngine-List Digest Archive --- Total Messages Posted Wed 04/30/08: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:38 AM - Re: Re: Grooves (James, Clive R) 2. 04:15 AM - Re: Re: Grooves (Lynn Matteson) ________________________________ Message 1 _____________________________________ Time: 01:38:15 AM PST US Subject: RE: JabiruEngine-List: Re: Grooves From: "James, Clive R" RE: the amount of grooves on the needle. This is my understanding. The early simple needles were gradually tapering and as such could be moved giving a richening or leaning of the mixture. The later needles look to be 'profiled' that is the diameter change isn't constant with length. Moving one of these needles by a groove may actually put the mixture out by a real step change rather than a tweak hence a single groove so it couldn't be done. Changing the needle jet size achieves the 'tweak'. Reference the 'profiled' needle. With a carburettor the whole business of air fuel mixture is a set of compromises, compromises which go along with the ones that come with our aircraft/propeller combination. There maybe a couple of speed/rpm setting that are optimum and there maybe a couple of speed/rpm/mixture settings that are optimum. Generally though things will always be less than the 'ideal'. When Jabiru in their wisdom started the 'Economy kit' and profiling needles there was one element that wasn't included and set the idea up for failure (this is in my opinion only). As the Jabiru engine is used in many planes the Aeroplane/propeller combination can be very different. In the Jabiru planes themselves different props and pitches (same numbers different pitches with Jabiru props) mean that the idea mixture requirements will be different. With different airframes different once again, in some cases and order of magnitude. So Jabiru produce a needle that runs the engine in cruise on the edge of too lean for plane X, great, we stick that engine on plane Y, Z, W and with prop this that or the other and it's not right...why should we be surprised. Anyhow just my sixpence worth (5 cents?) We had a strange one in the UK which I can't really understand. It is around the same issue as I mention above. A Jabiru J400 is built in the UK with a 3300 engine 'as supplied' (whatever that was at the time) three and a half years ago. It is flown happily for those three and half years until one day there's a running problem. Starts in the air and smacks of carb ice. Pilot circles over large airfield trying to isolate the problem. Carb ice suspected as problem began when entering a misty shower. Eventually nothing found and problem seems to go away. Continues to base. Two days later when flying the problem comes back and nothing will get rid of it, slight uneven running. Landing out at an airfield we check the plane over and by manipulating the throttle we can make it run like a bag of spanners and even stop. We get after the usual fault finding nothing found, certainly carburettor but what. Discussion with one of the UK agents engineers of the symptoms and he immediately suggests the mixture and a new needle jet. Other suggestions are tried 'in case' but it all points to a mixture problem. Eventually I drive across and get a selection of jets. Drive back and fit the 'next one up', and bingo as predicted, smooth as silk and I'm soon flying the plane back to base. So, my question is why, after 3 1/2 years (300 hrs same prop) does this problem manifest itself? Wear would richen things up, filters eliminated. ALL the checks show nothing. Just the jet to fix it...... The agent has been over and given it a dose of looking at and found nothing else. The jet needle combination has been matched correctly. One thing that is noted is it's running much cooler so was undoubtedly lean. But what changed to bring the problem on. Ideas? Regards, Clive List of what was checked Fuel filter Air filter Induction leaks Carburettor stripped completely and blown through and rebuilt. Float level Fuel, the same as another Jab that was flying over the same period Loads of other stuff I can't remember. -----Original Message----- From: owner-jabiruengine-list-server@matronics.com [mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Lynn Matteson Sent: 29 April 2008 16:23 Subject: Re: JabiruEngine-List: Re: Float Level --> Chuck- It must be that since your engine and mine, they changed their thinking on jet needles, and sent mine with only one groove. I have all three float needles, and I concur with your reading of 1.5 oz on the "silver-springed" light needle. My "gold-springed" medium needle scales at between 4-5 oz, and my "black-springed" high needle is in the plane at this time, so I defer to your reading of 31 oz. The silver, gold, and black colors are what I observed, and are not "official" by Bing. They refer to the three needles as "float needle light" , "float needle medium", and "float needle heavy." I ended up with all three due to various fartings around with the carb. I'm pretty sure the number of my main (#220) conforms to the size etched on the carb, but as Andy said earlier..... "You may also be unaware that Jabiru went through a phase a few years back of drilling-out jets to achieve the required mixture, so what was stamped on the jet wasn't necessarily the size of the hole.....This was from memory on 2200s before the year 2000, or so, but ask your dealer as they have factory information (I'm afraid I don't at present). To compound the issues, my understanding is that the sizes stamped on main jets don't correspond to the jet diameter, but on needle jets they do! This means a 2.80 needle jet has a 2.80mm hole, but I'm pretty sure a 255 main jet isn't 2.55mm. I have no clue why this is." .....that number may or may not be of value. Lynn Matteson Grass Lake, Michigan Kitfox IV Speedster w/Jabiru 2200 flying w/490+ hrs On Apr 28, 2008, at 10:15 AM, Chuck Deiterich wrote: > > > Lynn, > > I am sure I have a needle with several grooves. > When I replaced the float needle with one that has a stronger built in > spring (black), I did not readjust the float. The spring in the old > needle (orange) would compress at 1.5 Oz, while the spring in new > needle takes 31 Oz to compress (yes 20 times more). This means that > any compression of the weaker spring would effectively have a higher > float level. Thus my float may be a bit low. The 255 main is larger > than what Jabiru now puts in the Bing. SB 18-1 says mine came with a > 250 but it did not, as the main jet size is scribed in the side of the > carb body and on the jet itself. Lately they are using a 245 main > jet. Needle jet sizes can be misleading as the needles used are > different. > > Chuck D. > > >> >> Time: 04:47:22 PM PST US >> From: Lynn Matteson >> Subject: Re: JabiruEngine-List: Float Level >> >> >> The Bing manual for the carb says NOT to change the float (from what >> they suggest) to cure a problem, but to cure the problem by >> addressing either the main, the needle jet or the jet needle, >> whichever "neighborhood" the problem resides in (my analogy). I've >> read of guys who have adjusted the float height, but Bing says not >> to. Are you sure you have a "lowerable needle"? Mine is not, having >> only one groove for the snap ring. >> > > ________________________________ Message 2 _____________________________________ Time: 04:15:46 AM PST US From: Lynn Matteson Subject: Re: JabiruEngine-List: Re: Grooves Maybe the faulty jet or passageways leading up to the jet got a buildup of varnish or other contaminants over the years, and finally something dislodged and caused the problem. That's a strange one alright. Lynn Matteson Grass Lake, Michigan Kitfox IV Speedster w/Jabiru 2200 flying w/490+ hrs On Apr 30, 2008, at 4:34 AM, James, Clive R wrote: > > > So, my question is why, after 3 1/2 years (300 hrs same prop) does > this > problem manifest itself? Wear would richen things up, filters > eliminated. ALL the checks show nothing. Just the jet to fix it...... > The agent has been over and given it a dose of looking at and found > nothing else. The jet needle combination has been matched > correctly. One > thing that is noted is it's running much cooler so was undoubtedly > lean. > But what changed to bring the problem on. > > Ideas? > > Regards, Clive > > List of what was checked > Fuel filter > Air filter > Induction leaks > Carburettor stripped completely and blown through and rebuilt. > Float level > Fuel, the same as another Jab that was flying over the same period > Loads of other stuff I can't remember. > > -----Original Message----- > From: owner-jabiruengine-list-server@matronics.com > [mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of > Lynn > Matteson > Sent: 29 April 2008 16:23 > To: jabiruengine-list@matronics.com > Subject: Re: JabiruEngine-List: Re: Float Level > > --> > > Chuck- > > It must be that since your engine and mine, they changed their > thinking > on jet needles, and sent mine with only one groove. > I have all three float needles, and I concur with your reading of > 1.5 oz > on the "silver-springed" light needle. My "gold-springed" medium > needle > scales at between 4-5 oz, and my "black-springed" high needle is in > the > plane at this time, so I defer to your reading of 31 oz. > The silver, gold, and black colors are what I observed, and are not > "official" by Bing. They refer to the three needles as "float needle > light" , "float needle medium", and "float needle heavy." I ended up > with all three due to various fartings around with the carb. I'm > pretty > sure the number of my main (#220) conforms to the size etched on the > carb, but as Andy said earlier..... > > "You may also be unaware that Jabiru went through a phase a few years > back of drilling-out jets to achieve the required mixture, so what was > stamped on the jet wasn't necessarily the size of the hole.....This > was > from memory on 2200s before the year 2000, or so, but ask your > dealer as > they have factory information (I'm afraid I don't at present). To > compound the issues, my understanding is that the sizes stamped on > main > jets don't correspond to the jet diameter, but on needle jets they do! > This means a 2.80 needle jet has a 2.80mm hole, but I'm pretty sure a > 255 main jet isn't 2.55mm. I have no clue why this is." > > .....that number may or may not be of value. > > > Lynn Matteson > Grass Lake, Michigan > Kitfox IV Speedster w/Jabiru 2200 > flying w/490+ hrs > > > On Apr 28, 2008, at 10:15 AM, Chuck Deiterich wrote: > >> >> >> Lynn, >> >> I am sure I have a needle with several grooves. >> When I replaced the float needle with one that has a stronger >> built in > >> spring (black), I did not readjust the float. The spring in the old >> needle (orange) would compress at 1.5 Oz, while the spring in new >> needle takes 31 Oz to compress (yes 20 times more). This means that >> any compression of the weaker spring would effectively have a higher >> float level. Thus my float may be a bit low. The 255 main is larger >> than what Jabiru now puts in the Bing. SB 18-1 says mine came with a >> 250 but it did not, as the main jet size is scribed in the side of >> the > >> carb body and on the jet itself. Lately they are using a 245 main >> jet. Needle jet sizes can be misleading as the needles used are >> different. >> >> Chuck D. >> >> >>> >>> Time: 04:47:22 PM PST US >>> From: Lynn Matteson >>> Subject: Re: JabiruEngine-List: Float Level >>> >>> >>> The Bing manual for the carb says NOT to change the float (from what >>> they suggest) to cure a problem, but to cure the problem by >>> addressing either the main, the needle jet or the jet needle, >>> whichever "neighborhood" the problem resides in (my analogy). I've >>> read of guys who have adjusted the float height, but Bing says not >>> to. Are you sure you have a "lowerable needle"? Mine is not, having >>> only one groove for the snap ring. >>> >> >> >> >> >> > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message jabiruengine-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/JabiruEngine-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/jabiruengine-list Browse Digests http://www.matronics.com/digest/jabiruengine-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.