And some video with my own JBA 56.

[youtube]http://www.youtube.com/watch?v=wJOxwJiV75s[/youtube]

[youtube]http://www.youtube.com/watch?v=2NGQJXr24SI[/youtube]

[youtube]http://www.youtube.com/watch?v=3AlEuV7Fz_E[/youtube]

I know this is an old post, but I will try it anyway.
I have had a JBA .56 ABC for a couple of seasons, and it has worked well. A few weeks ago, it started acting strange. For example,
it would work fine with the plane flying right side up, but as soon as I would fly inverted it started sputtering. The strange thing is, it is side mounted,
so it should not matter which way the plane is flying. The it started giving me dead sticks. So I took the tank out, rerouted the lines to avoid kinks.
Today, I was only able to get one flight out, which ended in a dead stick. Flew fine for a few minutes, then during a pass over the runway at mid throttle I opened the throttle and the enngine quit.
The problem was quitting when opening up the throttle.
After readjusting the HSN, I leaned out a little bit the LSN, which solved the quitting while opening up. But then it started quitting
when closing the throttle! It was a nice day with temperature in the mid 60s F, or about 15 C. Fuel is Omega 10%, which is what I always use.
The only thing with the fuel I can say it is a bit old (6 months) and the just is almost empty... Plug was OS #8, prop 11x6.
Any suggestion is welcome. As I said, it worked fine so far, good response, power,
so I would like to keep it if at all possible

Thanks for reviving an interesting old thread! How's the compression..... still have a pinch at the top? If you don't solve it soon, I would pull the engine and run it on a test stand for comparison before it costs you the plane.

Compression is still good.

I would suspect a fuel tank issue

This is the first thing I thought too, when I started having engine issues flying inverted. The tank sits level with the carb. Moreover, it worked fine for a long time.
Anyway, I reseated the tank, and rerouted the fuel line to avoid a possible kink in the line. But that did not fix it.
I will try to pressure test the system to ~ 10psi to check for leaks. I still think the problem is with the LSN. Years ago I had a glow heli with a TT engine and remember that slightly changing the taper of the LSN
made tuning much easier... Chinese carbs can be a PITA.

I would look carefully for garbage in the fuel inlet, needles and fuel and exhaust nipples. Since it was running great it seems that the low speed needle setting wouldn't just go bad. Still, I would put all my money on a fuel tank issue as others have already said. Not just for leaks in the tank or plug, but perhaps a hole or cut in the inlet line attached to the clunk inside the tank. That's what it sounds like to me!

These small holes have given me fits in the past. Any air bubbles in the line at the carb during high throttle?

Just to clear things up, I under stand that the engine ran good in all attitudes, then started dying when flying inverted, then started dying during any type of flight.

Was there a time laps between flying good and dying during inverted flight, like say a winter non flying season, or did this just happen overnight, as in Saturday it flew inverted without problems and then the next Saturday it died during inverted flight.

My first guess would be a pinhole in the fuel line inside the tank. Some of my planes however, after sitting through the winter, sometimes get "floatys" in the fuel tank, which are little chunks of debris from the oils used. The floatys don't seem to re-dissolve in the fuel when you start flying again, they just float around and clog the needle valve intermittently. These floatys do not have to be very big to give really strange results with the running of an engine.

Another theory that just came to me is perhaps your exhaust pressure line is being clogged somewhere. Maybe the muffler nipple. Perhaps the little extra pressure of the fuel on top of the exhaust vent while inverted was enough to loose muffler pressure, and then the blockage got worse and eventually the tank was not getting any pressure at all. I could see that depending on how the plane was stored (if stored) through the winter, some debris could have plugged up the exhaust line a little bit.

A hole in the exhaust pressure line could also cause the same problem. The hole could stay somewhat closed with low pressure and then open up when under higher pressure.

These are all good ideas. I think the plane sat a month or so. We do not really have winter around here. At the most, we can go a couple of weekends with bad weather.
One more thing. I mentioned the fuel jug was almost empty. Today, I held it against a light, and noticed that it was not clear (aside from the pink color). There is some stuff, not
like sediments, more like gunk sloshing around, and the pink is definitely darker than the pink in a new jug. I wonder if that is the culprit.
I guess they are right when they say one should not put unused fuel back from the tank into the jug....

Well, there goes my theory about bad fuel. Flown my old trainer (TT .46 Pro) with the old fuel with no problem whatsoever. I have to say that the TT .46 is probably the most reliable engine I ever had. Bought it used, been in several planes, at least twice ended up in a lake and yet still fires as if it had been just taken out of the box. Next I will start checking the lines starting from the clunker and making my way up to the carb...

I agree with the TT46Pro, mine is amazing.

Mine is fantastic too. First airplane engine I ever got. Takes a beating and keeps on ticking (over). Unfortunately I haven't heard the same about JBA... :?

Brief recap: engine started acting strange, leaning out at the top of outer loops or when flying inverted, even though the engine is side mounted.

I worked on if on and off for many months, until I ended up drilling another hole in the firewall for the fuel line. After rerouting the fuel line, all problems magically disappeared.
I think the problem was either the fuel or the pressure line pinching when subject to g forces.
Now the engine is very happy. I also switched from a MA 11x6 that I had before with a APC 12x4. Tached it at 13100 (Omega 10% nitro, 85F external temp, stock setup), with 6 hours on the clock.
Now I am thinking about removing shims, though I may just enjoy it for a while.
The Something Extra loves the new prop. Had to increase the tires from 2.5" to 3" to provide enough ground clearance.
Thanks for all who contributed ideas.

Awesome, fuel line issues are always at the top of my hit list

My JBA .56 is acting up again. Last time I used it (in January 2017, 50F) it ran fine. Today, with the temperature above 70F, I ran into trouble. Many times it would just die during the takeoff roll, and several times it dead sticked in the air. In all cases the feeling is that the engine is getting lean. Note that the problems I had in the past year the engine never actually quit.
Putting a new Enya #3 worked for one flight, then it was back to quitting. I took the head off and noticed that there is hardly any pinch at the top. Could that be the problem? and if so, where can I get a new piston/sleeve set? I could also try to remove the copper gasket and see if the increased compression helps... This time, the problems appear in normal attitude, e.g. during the takeoff roll.