Jabi running rough

[Neophron]

The guys that "knows" says the float and needle looks OK.???
Fuel pump on or of, just the same.
No fuel from the overflow.
All the plugs are badly fouled.
(I think what she needs is a good carb tune by some one that really knows what he is doing. But thats just me, I don't call the shots its not my plane I'm just trying to help.)

On the hot air, the way I see it: Hot air is less dense than cold air thus less oxygen, the flow stays the same thus the same amount of fuel but less oxygen to burn it. Apply carb heat and the rpm's drops.

[justin.schoeman]

The guys that "knows" says the float and needle looks OK.???
Fuel pump on or of, just the same.
No fuel from the overflow.
All the plugs are badly fouled.
(I think what she needs is a good carb tune by some one that really knows what he is doing. But thats just me, I don't call the shots its not my plane I'm just trying to help.)

On the hot air, the way I see it: Hot air is less dense than cold air thus less oxygen, the flow stays the same thus the same amount of fuel but less oxygen to burn it. Apply carb heat and the rpm's drops.

What was I thinking... of course hot air makes it richer! For some reason that one always catches me.

Have you tried any full power ground runs - then immediately take out a plug and inspect? Will give you an idea if it is an intermittent problem or not?

[John Boucher]

When all the plugs look the same my logic says you look for something common & shared between all cylinders

So, sort out all electrical stuff that is common.....

Then sort out the fueling.....

[Neophron]

Hi.
Haven't got all the info yet, but it seems as if the problem ly's with the main jet. It seems to be to big
Still investigating. Will post more info when I get it...

[James Bentley]

If you are prepared to do another run, take off and as soon as the engine starts to run rough throttle back slightly. This will prevent the over rich mixture. What could be occuring is that as soon as the engine speed goes up and the prop "unloads" due to the airspeed increase the engine cannot cope with the excessive amount of fuel, the meetering needle could also have become dislodged from its clip retainer. It would appear that your problem arises in the upper rpm band where the main jet operates. If the needle is too high (not in place) an over rich condition can occur. My conclusions arise from you indicating that the problem is getting worse meaning that something has worked loose, or is in the process of coming loose??

If in doubt ask Jabiru SA to send you another carb, that is if the engine came from them.

Maybe do not attempt another take off and fly a circuit, check everything first again.

Let us know...

Goodluck.

[Jabbanaught]

Hi guys!
A friend and I just finished building his new Skyranger Swift with a Jabiru 2200 (85Hp) engine. The Jabi started first time and pured like a kitten over a bowl of milk during the ground testing. Even on her maiden she performed beautifully, but around her third hour she started running rough after take of while doing touch and go's....He did a mag check and the right mag dropped more than double the allowed rpm. She was grounded and given some TLC... all wiring checked, carb inspected, could it be carb icing... no carb heat was used... could it be a bad spark plug and why are the spark plugs so black, so change the plugs... Started her again and their she was back puring with no problems! Took her flying for 35 minutes no problem! Later it was time for another flight and the problem popped out again... on the ground this time while doing the mag checks. When the left mag is switched of the engine runs very rough with hi rpm drop....? First right now left? Could the engine be running to rich and fouling up the plugs? From time to time while on the ground you can see smoke coming out the exhaust, not much but visible smoke. Is this normal? He is running her on 95UL. All temperatures and pressures perfectly in the green. We are a bit lost here ... any thoughts ?

Contact Len at george factory he is always willing to help 044-8769991

[Ranger]

What colour is the smoke?

[Neophron]

Hi. Sorry I have been very busy lately, and it is very difficult if you live in the middle of nowhere.
My friend took the carb of and has send it to Jabiru on the request of Len. Just another week with out flying...
Will keep you posted.

[Neophron]

Hi Guys.
My friend finally got his carb back from Jabiru. Len and his staff has been very helpful. They found a manufacturing flaw in the carb. Apparently a small equalizing tube wasn't drilled through all the way... This tube was suppose to let air through ... instead it sucked more fuel making it run rich.

Now could some one please explain .... This engine was run in and tested. Why did it almost ruin a brand new plane or even worse almost kill some one?

Well the engine is puring again and every thing seems fine so far. Let's see how she does with more testing...

Cheers

[Fish from MX]

Hello from Mexico

Just having the same problem. Already e-mailed to Les at Jabiru. Thank you for share your knowledge

Saludos!

[Jean Crous]

Hi Fish from MX ! Welcome to the forum.
Jean

[Boet]

The float will be suspect. When the fuel is cold it drifts, and when it heats up, it sinks, causing your over rich problem. Try fitting new carb float. Had this problem many years ago on a chevvy V8. In the boycot years. Float nowhere available, so I made one out of a Coke tin, and it worked fine for many thousands of km`s untill I eventually found another one.

[Johannvanniekerk]

He said it happened on the ground as well
Hot HT lead that could be damaged