Leaking Bing Carby

[rmccoy8]

Hi I am having trouble with a leaking Bing Carby on my 80hp 912. After engine shutdown I noticed a pool of petrol on the ground and traced it to a fuel leak from the air intake side of one of the carbys.The fuel had leaked from the carby, made its way through the heater box and oozed down the firewall onto the ground.I thought I'd fixed this problem but I later detected a strong smell of fuel whilst in the air and a subsequent inspection revealed fuel had leaked onto the lower fuselage above the undercarriage.It had come from the same carby and the air intake pipe was saturated. Has anyone else had a problem like this and I'd appreciate any thoughts on how to fix it.

 

Cheers Richard

 

 

[Captain]

Richard

 

If it was me, I'd start by checking the float level in that carby and the needle valve which the float controls.

 

It might be high level, or a fault in the needle or seat, or most likely just some foreign matter holding the needle open a tad, and it doesn't take much.

 

When checking it, also turn on fuel pump and flush out that line (and catch the contents so that you can see any foreign muck that might come out).

 

If you find anything you need to identify where it has come from as that will indicate that there must be an issue with your fuel filter or perhaps a problem with the inside of the fuel line or similar.

 

If there is muck getting thru to the problem carby, then you need to do the same for the other carby.

 

Also clean out anything that might be in the bottom of both float bowls.

 

Hope that gives you somewhere to start.

 

Regards Geoff

 

 

[Admin]

While you are at it Richard, just check the fuel pump serial number with the recall:

 

http://www.recreationalflying.com/forum/aircraft-ads-ans-list/1267-rotax-engines-2.html#post15205

 

 

[Guest Maj Millard]

Page 10-1 of the Rotax Operators manual (assuming you do have one ) says the following :Note. exceeding the max admissable fuel pressure will overide the float valve of the carburetor.

 

The delivery pressureof an additional backing pump (eg: electric standby pump) must not exceed 0.3 bar (4.4psi) in order not to overide the float valve.

 

The Bing in my experience is a pretty hands off type carb, once it is set up and adjusted correctly. The do seem to flog out at around 700 hrs or so and then require a rebuild kit inc a new diaphragm, to put them right again. As they wear they tend to get richer, for many reasons of which I won't go into here. A lot of problems arise because people mess with the carb bowl equilization tube (clear plastic) believing it to be a fuel overflow tube and re routing it. Its primary purpose is to maintain atmospheric/ambient pressure on top of the fuel in the fuel bowl so the carb can work correctly. Hope this helps. Ross Millard L2 Geoffs recommendations (previous entry ) was also good stuff and worth doing.

 

 

[rmccoy8]

Carby problem fixed

 

Thanks Geoff, Ian and Ross for your helpful suggestions.I had the carby bowls cleaned at the factory and they contained fine particles of dirt as well as some watery sludge.I also replaced all fuel lines beyond the on/off taps and inserted an additional fuel filter before the gascolater.This seems to have fixed the problem as no leaks were evident after a couple of test flights.It looks like it was a dirt issue all along.

 

Cheers Dick McCoy