Ask George

[ZuluBen]

Leon, ground running for longer that 30 seconds is a no no

You will overheat the heads and cause yourself endless and dangerous problems.

And you are going to need to run for several minutes to see REAL temps

[HappyJabi]

Leon, ground running for longer that 30 seconds is a no no

Ben, thanks for the advice but with respect, are you saying that if one is not airborne within 30 seconds of starting the engine your engine is at risk?

Have you ever fit the needle and jet kit (econ kit) I have sent you.

Francois, you sent me jets. No needle and no, I haven't fitted them. The CHT and EGT on the one side of the engine are perfect, and the other side is extremely low and getting worse. The engine was tested and ran perfectly (according to Len and I believe him) at the factory. After installing into the airframe this anomaly existed. I finally have some advice (from Len) that makes sense to my computer program writing logical mind. Len is sending me a "Cobra Head Duct" to fit at the entrance to the carb that ensures smooth airflow and that the the sensing ports are not obscured. While waiting for this duct I can prove the point by running the engine briefly without the scat hose connected. Clearly the air needs to be filtered hence the need for a pancake filter.

I'm hoping that once I cure this problem the information can be useful to others.

[BigglesSA]

So installation caused this problem?

[ZuluBen]

HappyJabi » Fri Aug 30, 2013 9:29 pm
Ben, thanks for the advice but with respect, are you saying that if one is not airborne within 30 seconds of starting the engine your engine is at risk?

No, you can idle / taxi it all day long without a problem, but we are talking full throttle here ....

And if you run her at full throttle in the chocks for prolonged periods of time, you WILL cook the heads and drop the valves / valve seats ..

The motor NEEDS the higher airflow that comes with flight speeds to keep the temps in check.

Gottit?

[HappyJabi]

No, you can idle / taxi it all day long without a problem, but we are talking full throttle here ....

Gottit?

I do. Thanks for that Ben, but I won't need to use full throttle to see what I want to see. 1500 to 2000 rpm for a very short period is enough. Problem is that the only pancake filter I found so far is too big for the space available there.

So installation caused this problem?

We'll know for sure soon enough. With the rather serious damage that was done to the silencer box for instance I don't know what else could have been hurt. I'm afraid I haven't got the nerve to actually remove the carb so I'll have it done by an AMO shortly.

[HappyJabi]

image.jpg

During a recent MPI this part was replaced because it is cracked. I understand it drives the vacume pump? During this morning's flight the vacume pump stopped working. I can't get hold of the AMO at the moment. Can anyone perhaps advise where I can start looking for the problem?

[Swampdonkey]

The dive shaft inside most vacuum pumps have a weakened point which is to ensure that the shaft shears instead of the drive assembly, thus keeping the damage in the pump itself rather than the engine.your problem could be this, or that the vacuum driven gyro instrument filters are blocked.

[HappyJabi]

The dive shaft inside most vacuum pumps have a weakened point which is to ensure that the shaft shears instead of the drive assembly,

Spot on FB. The nylon coupling sheared. The AMO tells me vacuum pumps typically last 600 to 800 hours. Can the ou manne tell me if this is their experience? He wants to sell me a new pump but fortunately I spoke to Les Alford who assures me she can supply the coupling. Big thank you Les. To the rescue as always.

One more question. I notice the pipe hanging freely is connected to the "OUT" side of the pump. In other words the pump sucks from the instruments rather than blow to them. Is this correct? Keep in mind the pump had been removed during a recent MPI.

*Edit*. Is there something that can be done to remove unnecessary stress from the pump to make it last longer?

[ZuluBen]

Leon wrote:

One more question. I notice the pipe hanging freely is connected to the "OUT" side of the pump. In other words the pump sucks from the instruments rather than blow to them. Is this correct? Keep in mind the pump had been removed during a recent MPI.

Indeed.

It has to generate a vacuum, so it effectively "pumps in reverse".

It is advisable not to turn the engine the wrong way round if it could be avoided, as the little carbon vanes in the pump tend to wear a directional face on them, and this could get stuck when the pump is reversed.

Lifespan of these things should really be about 2000 hrs.

Wynand, have you replaced yours yet?

[jjt1101]

Len, i wont say its overdue but certainly a huge need amongst the owners and certainly would help your product to reach new levels ito sales following trust, reliability etc. and will therefore result in a even stronger Jabbie cohesion.
All the best and looking forward in following.

[crazeeflya]

Maybe i'll get a decent answer here?


Greetings Len and Marilyn,


I was supplied new brake callipers by Jabiru late last year.

Firstly the brake line fittings would not screw in by hand and on investigation it was found that the threads were not properly tapped.

I purchased a tap (sale slip attached) and cleaned threads to point where fittings screwed in correctly.

On fitting the first calliper to aircraft, the bleed screw transferred from the old calliper failed to seal even at zero pressure…ie I filled cylinder with fluid holding it level and fluid dribbled past bleed screw. Subsequent tightening of same screw resulted in it breaking off…and still leaking even with that amount of torque.

I drilled out broken nipple and purchased a ¼ tap today to clean up.(sale slip also attached)

On inspecting the other, up to now brand new and unfitted calliper, I discovered why the bleed screw will never seal.

The seat of the bleed hole is both oval and damaged.

I attach photo of the brand new unused calliper showing same.

Can I request please that a decent pair of callipers which have non-leaking bleed screws fitted be sent to me as a matter of urgency.

I have already spent in excess of R600 in freight on unusable parts and thus think it only fair that these be sent free of charge and freight cost to me.

I will gladly package the unserviceable parts and return these at your expense so you can maybe rework them to usable status.

All I want is to be able to use my plane and we are now starting the third month of her standing grounded.

Kind regards and Happy 2014
Craig Cox
083 441 8490

[Namibfox]

.

[dupwillie]

Geduldig wees ek het 9 maande gewag vir my jabi

[Namibfox]

.

[dupwillie]

Sorry you must have patient if you want a Jabi rather buy it second hand no waiting list and all snags sorted out