Bing carburettor 2200

[lee-wave]

Cold Start Notes Jabiru 2200.doc        

[Markdun]

Interesting.   A couple of comments.  First, what you describe is not a choke, but the starting enrichening system of the Bing CV carb (semantics I know, but it can have a consequence if you think it is a choke) . Second, the large hole in the enrichening metering disc does not need to be exactly lined up with the hole in carb body; it only needs to be open to that port which is pretty wide...as it needs to be so as the metering disc is rotated and the largest hole is covered up the next size hole (less rich) is uncovered. Third, at 2000rpm the enrichening system would be mostly bypassed as it needs the throttle butterfly to be closed to work.  That is why one needs the throttle fully closed for the Bing enrichening system to work... it provides both fuel and air for a rich fast idle.  A mistake people can make is to think that cracking the throttle open a bit (like a traditional choke) will help start a cold Jab...it won’t. Unlike a choke it will make little difference if any at all once the throttle is opened.  It needs a big difference in MP vs inlet air pressure (vacuum if you like).  Try pulling the enrichener at cruise throttle settings and watch your EGTs.... you may be surprised that they increase or stay the same... mine increase a tad.  So don’t expect it to provide more fuel at higher than fast idle rpm.
I have heard of ppl drilling the largest hole in the metering disc a bit larger... maybe your mod is easier, but I’ve never had a problem starting my two Jab2200s when cold: turn fuel on, turn mags on, close throttle fully, pull enrichening knob while pressing starter... engine starts once fuel fills the carb bowl in maybe around 12 compressions (if fuel in bowl, then usually in 3-6 compressions). Lithium battery, so no problem cranking.  Once engine fires up I let the enrichening knob go (it returns to off from the spring on the Bing) and adjust the throttle for fast idle.

[facthunter]

The main thing to realise is have the throttle fully closed or B-all fuel will enter the mixing chamber. In very cold conditions the "Choke" has to be left on longer. before you crack the throttle at all.. It's a slightly better set up than the old Solex Carburetters used, but the same principle. Has more stages. The mixing  chamber adds air as well as fuel. and it comes out after the throttle butterfly. Nev

[Markdun]

Nev, in anything less than 5 Celsius I pull carb heat for start too....yeh, yeh the exhaust is not hot right at a cold start, but it heats up bloody quick. Mark

[facthunter]

When people understand what's going on they will operate better. IF you just do what you have been told to do,(" Rote" Learning) You can't troubleshoot or adjust for variables so readily and appropriately. Like most things it's not rocket science. Nev

[kgwilson]

I had problems starting my Jab engine initially when it was very cold. The solution was incredibly simple. Close up the plug gaps a bit. 1 or 2 thou is all it takes. Never had a cold starting issue since even when there was ice on the wings. Having a good battery that will perform at very low temperatures is also essential. The Jab engine must turn over at 300 RPM before the transistorised ignition will produce any spark.

 

I know some owners have had cold starting problems though especially those who live in places where the Winter temperatures stay around 0-5 degrees during the day & minus whatever at night. Jabiru did produce a cold start kit some years ago that included a secondary coil that induces voltage from the battery regardless of engine cranking speed. I don't know if they still produce them.

 

 

 

Edited February 5, 2022 by kgwilson