Greetings,
I have a 2200 solid lifter Jab that I believe may need to have the main jet and or needle jet replaced. The EGT’s are between 1400 - 1500 degrees F (760 - 815 C) in cruise flight which makes me think this is running too lean. Spark plug inspections confirm this as they have turned from a brown in warmer weather to a very light tan now in winter. I removed the carburetor and the jets; main jet is a 255, needle jet is a 2.76.
Any suggestions on what size larger jets to enrich the mixture? According to the Bing tuning instructions attached, the main is used for climb and the needle for cruise. I don’t want to start randomly changing but I imagine anything larger will help.
It appears that the colder weather results in leaner mixtures. It makes sense since the air is denser and that means more air molecules to the same volume of fuel which reduces the fuel to air ratio. I didn't have EGT probes installed during the summer so the only comparison I can make is based on the color of the sparks plugs as mentioned before.
I had a Jab owner suggest the HACman mixture controller. He recommends to tune the carburetor on the rich side and then lean it using the controller as necessary until optimal EGT's are reached.
Thanks,
Alex R-
Hello Alex,
Just let me say now, here at Jabiru, we really don't like the HACman. There is too much potential for things to go wrong. I.e forget and on descent have a flame out or unintentional lean mixtures.
The first step in tuning the engine is to determine what needle the carburettor has. The recommended one has a pronounced narrow tip (called jabiru economy). With these needles we run 290 needle jet, a 235 main and a 45 idle.
Thanks. I’ll look to see what style needle was installed. This is the original Bing CV 94 carburetor Jabiru installed on this A2200 in 2001.
According to service bulletin JSB 018-2, my A2200, serial number 22A981 was manufactured before the introduction of the economy kit. Should I then consider the economy kit #4A172A0N?
Well not the economy tuning kit as such, but definitely get the jabiru needle for your engine and the jets. The result is that the mixture is able to run leanish to about 2900rpm and then it richens up. I have a solid lifter engine with this combination (I have a 285 needle jet but it is quite warm here) and it is running very well. Cruise egt is just over 710C at sea level.
Jabiru P/No. 4A131A0D-3, according to the bulletin? I assume I can get that in the US?
P/No. 4A138B0D-2 You should be able to get it. If they don't have it they will just order it off us.
Greetings Jab support,
Is there any value in drilling the idle circuit inlet aperture to 1.6mm? If so, is there a detailed procedure from Jabiru? Also, the print on JSB 018-2 references LLD at the aperture. What is that?
Thanks,
Alex R-
Hello Alex,
So JSB018 has been cancelled. We don't drill them out anymore.
So the answer is basicly no.
I can't find LLD in JSB 018-2 so I can't help you there.
Just curious on the LLD, no worries. Thanks for the answer on drilling, or not to!
Alex R-
Greetings Jab support,
What position should I place the Jabiru needle? I assume there are position grooves as in the Bing needle?
Thanks in advance!
Alex R-
Hello Alex,
The Jabiru needles only have one position. So no need to worry about that. 😉
Greetings Jab support,
I installed the Jab needle and now the engine quits when I add power from idle. It seems as if it's starved for fuel. I'll make sure I didn't screw up the installation of the needle and the assembly. Mind you, I had the carburetor apart before to inspect and to see what size jets it had. I had installed the 45 size idle jet but it was too rich and produced soot on the spark plugs and exhaust pipes. I replaced that with the original 35 as you recommended. I left the main at 260 and the needle at 2.79. These jets were increased in size to reduce EGT's at climb and cruise, which it did by the way. Any suggestions as to why it abruptly quits when I add power from idle after installing the Jab needle?
By the way, thanks for you consistent help, it's always appreciated!
Alex R-
Hello Alex,
What is happening that the engine is starving for fuel as it comes off idle. Can you tell me what is the part No. of needle you got?
The solution is a bigger needle jet. We use a 290 needle jet and 245 or 235 main jet with the jabiru needle but I will be able to confirm that when I have the part number. Additionally you can sneak up to it by trying a 285 needle jet first. I think you will find a 260 main is will be rich at full power.
I ordered
