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Jett 56 help with Jackal 50

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Old 05-03-2011, 06:26 AM
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txshan130
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Default Jett 56 help with Jackal 50

Has anybody else had problems getting the Jett 56 to run reliably with the Jett bubble free tank? It's a pretty tight fit in the Jackal. Engine ran fine on the test stand but now I can't seem to get the needle valve set....as soon as I lean it out to get it staged on the pipe, it wants to die on me....going to take out the Jett tank next and try a regular one. This has been very frustrating.... Picture of setup is after replacing the Jett tank with the stock H9 tank.

Also Idid unfortunately remove the needle valve without loosening the nut all the way (before reading the instructions :-() but that was before running it on the test stand where it ran just fine. Also don't see any leaks in the lines at the needle valve so guessing I didn't hurt it...


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Old 05-03-2011, 07:38 AM
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Default RE: Jett 56 help with Jackal 50

when you ran it on the test stand did you run it on that plastic mount?? if not remount engine on test stand and re test the engine. i have had MANY problems with plastic mounts on these engine and always use a metal one. either a beam or bulkhead type.
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Old 05-03-2011, 09:01 AM
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Default RE: Jett 56 help with Jackal 50

Ran it on a different mount on the test stand...it was actually one with wood blocks that clamp down.
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Old 05-04-2011, 07:23 AM
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Default RE: Jett 56 help with Jackal 50

Quite the opposite - I do not have a .56, "just" a .50 - but the Jett tanks work very, very well and improve consistency, not hurt it. I also have run them on piped .65 DF engines which pull 4oz/minute, without trouble.

If it runs on the test stand with that tank but not in the aircraft - something has changed. There has to be something else going on IMHO. The folks from Jett preach solid mounting, these engines generate a lot of power for the package size and need to be mounted solidly. I agree with rc's comments.

The big question is - when you changed tanks did the needling improve? Y - then it was something to do with the tank installation. N - then it is a separate issue.

Hope you get it worked out. Bob should be along here any time, he's "the man".

Same prop? Looks like 6" pitch but can't tell the diam.
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Old 05-06-2011, 10:57 AM
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Default RE: Jett 56 help with Jackal 50

First things first......

put it back on the test stand. Run it. Get a baseline. Make sure everything works well. You can try a few needle valve locations high... low... behind, over - you may be amazed how little difference the needle location makes.

Get the engine set up there, with the bubble tank. (Question, are you using the Jett tanker, or another device to fuel from?).

The bubble-jett tank does not cause the engine to run any differently, it simply prevents air from mixing in, and this helps avoid lean runs caused by sucking an airbubble when the tank level gets low. Generally improves the way the engine runs if anything because the fuel delivery is more consistant.

Once you have the engine running well on the test stand, put it back in the plane. It should run exactly the same. If it misbehaves, you know exactly where the problem is.

On my old VQ P-51, I put a perfectly good running SJ-46 and turbo-jett combination on the nose. It ran like crud. In that case, I could actually see the motor mount flexing. I replace it with aluminum rails (Sig at the time made a perfect replacement set). Instantly solved the problem. Stock fuel tank in this one too. After 7 years it still runs great. Just an example of how the installation or airframe can be part of the problem.

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Old 05-06-2011, 11:06 AM
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Default RE: Jett 56 help with Jackal 50

Hi Bob,I plan on trying it back on the test stand this weekend with the Bubble Jett tank and in the meantime buying an aluminum motor mount as well....I think you said the aluminum mounts for the OS 46 will work.Will this one work? Guess my question really is about the bolt hole spacing for the Jett 56 vs the OS 46 series...is the spacing the same since the OS mount is pre-drilled? OS 71913100 Motor Mount 40-46FX/50SX/46AX/55AXThx, Brian
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Old 05-06-2011, 12:10 PM
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Default RE: Jett 56 help with Jackal 50


ORIGINAL: txshan130

Hi Bob,I plan on trying it back on the test stand this weekend with the Bubble Jett tank and in the meantime buying an aluminum motor mount as well....I think you said the aluminum mounts for the OS 46 will work.Will this one work? Guess my question really is about the bolt hole spacing for the Jett 56 vs the OS 46 series...is the spacing the same since the OS mount is pre-drilled? OS 71913100 Motor Mount 40-46FX/50SX/46AX/55AXThx, Brian
Yes, that should work.

The bolt hole pattern is the same.
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