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1. 01:38 AM - Re: Re: Grooves (James, Clive R)
2. 04:15 AM - Re: Re: Grooves (Lynn Matteson)
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RE: the amount of grooves on the needle. This is my understanding. The
early simple needles were gradually tapering and as such could be moved
giving a richening or leaning of the mixture. The later needles look to
be 'profiled' that is the diameter change isn't constant with length.
Moving one of these needles by a groove may actually put the mixture out
by a real step change rather than a tweak hence a single groove so it
couldn't be done. Changing the needle jet size achieves the 'tweak'.
Reference the 'profiled' needle. With a carburettor the whole business
of air fuel mixture is a set of compromises, compromises which go along
with the ones that come with our aircraft/propeller combination. There
maybe a couple of speed/rpm setting that are optimum and there maybe a
couple of speed/rpm/mixture settings that are optimum. Generally though
things will always be less than the 'ideal'.
When Jabiru in their wisdom started the 'Economy kit' and profiling
needles there was one element that wasn't included and set the idea up
for failure (this is in my opinion only). As the Jabiru engine is used
in many planes the Aeroplane/propeller combination can be very
different. In the Jabiru planes themselves different props and pitches
(same numbers different pitches with Jabiru props) mean that the idea
mixture requirements will be different. With different airframes
different once again, in some cases and order of magnitude.
So Jabiru produce a needle that runs the engine in cruise on the edge of
too lean for plane X, great, we stick that engine on plane Y, Z, W and
with prop this that or the other and it's not right...why should we be
surprised. Anyhow just my sixpence worth (5 cents?)
We had a strange one in the UK which I can't really understand. It is
around the same issue as I mention above. A Jabiru J400 is built in the
UK with a 3300 engine 'as supplied' (whatever that was at the time)
three and a half years ago. It is flown happily for those three and half
years until one day there's a running problem. Starts in the air and
smacks of carb ice. Pilot circles over large airfield trying to isolate
the problem. Carb ice suspected as problem began when entering a misty
shower. Eventually nothing found and problem seems to go away. Continues
to base. Two days later when flying the problem comes back and nothing
will get rid of it, slight uneven running. Landing out at an airfield we
check the plane over and by manipulating the throttle we can make it run
like a bag of spanners and even stop. We get after the usual fault
finding nothing found, certainly carburettor but what. Discussion with
one of the UK agents engineers of the symptoms and he immediately
suggests the mixture and a new needle jet. Other suggestions are tried
'in case' but it all points to a mixture problem. Eventually I drive
across and get a selection of jets. Drive back and fit the 'next one
up', and bingo as predicted, smooth as silk and I'm soon flying the
plane back to base.
So, my question is why, after 3 1/2 years (300 hrs same prop) does this
problem manifest itself? Wear would richen things up, filters
eliminated. ALL the checks show nothing. Just the jet to fix it......
The agent has been over and given it a dose of looking at and found
nothing else. The jet needle combination has been matched correctly. One
thing that is noted is it's running much cooler so was undoubtedly lean.
But what changed to bring the problem on.
Ideas?
Regards, Clive
List of what was checked
Fuel filter
Air filter
Induction leaks
Carburettor stripped completely and blown through and rebuilt.
Float level
Fuel, the same as another Jab that was flying over the same period
Loads of other stuff I can't remember.
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Lynn
Matteson
Sent: 29 April 2008 16:23
Subject: Re: JabiruEngine-List: Re: Float Level
--> <lynnmatt@jps.net>
Chuck-
It must be that since your engine and mine, they changed their thinking
on jet needles, and sent mine with only one groove.
I have all three float needles, and I concur with your reading of 1.5 oz
on the "silver-springed" light needle. My "gold-springed" medium needle
scales at between 4-5 oz, and my "black-springed" high needle is in the
plane at this time, so I defer to your reading of 31 oz.
The silver, gold, and black colors are what I observed, and are not
"official" by Bing. They refer to the three needles as "float needle
light" , "float needle medium", and "float needle heavy." I ended up
with all three due to various fartings around with the carb. I'm pretty
sure the number of my main (#220) conforms to the size etched on the
carb, but as Andy said earlier.....
"You may also be unaware that Jabiru went through a phase a few years
back of drilling-out jets to achieve the required mixture, so what was
stamped on the jet wasn't necessarily the size of the hole.....This was
from memory on 2200s before the year 2000, or so, but ask your dealer as
they have factory information (I'm afraid I don't at present). To
compound the issues, my understanding is that the sizes stamped on main
jets don't correspond to the jet diameter, but on needle jets they do!
This means a 2.80 needle jet has a 2.80mm hole, but I'm pretty sure a
255 main jet isn't 2.55mm. I have no clue why this is."
.....that number may or may not be of value.
Lynn Matteson
Grass Lake, Michigan
Kitfox IV Speedster w/Jabiru 2200
flying w/490+ hrs
On Apr 28, 2008, at 10:15 AM, Chuck Deiterich wrote:
> <cffd@pgrb.com>
>
> Lynn,
>
> I am sure I have a needle with several grooves.
> When I replaced the float needle with one that has a stronger built in
> spring (black), I did not readjust the float. The spring in the old
> needle (orange) would compress at 1.5 Oz, while the spring in new
> needle takes 31 Oz to compress (yes 20 times more). This means that
> any compression of the weaker spring would effectively have a higher
> float level. Thus my float may be a bit low. The 255 main is larger
> than what Jabiru now puts in the Bing. SB 18-1 says mine came with a
> 250 but it did not, as the main jet size is scribed in the side of the
> carb body and on the jet itself. Lately they are using a 245 main
> jet. Needle jet sizes can be misleading as the needles used are
> different.
>
> Chuck D.
>
>
>>
>> Time: 04:47:22 PM PST US
>> From: Lynn Matteson <lynnmatt@jps.net>
>> Subject: Re: JabiruEngine-List: Float Level
>>
>>
>> The Bing manual for the carb says NOT to change the float (from what
>> they suggest) to cure a problem, but to cure the problem by
>> addressing either the main, the needle jet or the jet needle,
>> whichever "neighborhood" the problem resides in (my analogy). I've
>> read of guys who have adjusted the float height, but Bing says not
>> to. Are you sure you have a "lowerable needle"? Mine is not, having
>> only one groove for the snap ring.
>>
>
>
Message 2
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Maybe the faulty jet or passageways leading up to the jet got a
buildup of varnish or other contaminants over the years, and finally
something dislodged and caused the problem. That's a strange one
alright.
Lynn Matteson
Grass Lake, Michigan
Kitfox IV Speedster w/Jabiru 2200
flying w/490+ hrs
On Apr 30, 2008, at 4:34 AM, James, Clive R wrote:
> <clive.james@uk.bp.com>
>
> So, my question is why, after 3 1/2 years (300 hrs same prop) does
> this
> problem manifest itself? Wear would richen things up, filters
> eliminated. ALL the checks show nothing. Just the jet to fix it......
> The agent has been over and given it a dose of looking at and found
> nothing else. The jet needle combination has been matched
> correctly. One
> thing that is noted is it's running much cooler so was undoubtedly
> lean.
> But what changed to bring the problem on.
>
> Ideas?
>
> Regards, Clive
>
> List of what was checked
> Fuel filter
> Air filter
> Induction leaks
> Carburettor stripped completely and blown through and rebuilt.
> Float level
> Fuel, the same as another Jab that was flying over the same period
> Loads of other stuff I can't remember.
>
> -----Original Message-----
> From: owner-jabiruengine-list-server@matronics.com
> [mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of
> Lynn
> Matteson
> Sent: 29 April 2008 16:23
> To: jabiruengine-list@matronics.com
> Subject: Re: JabiruEngine-List: Re: Float Level
>
> --> <lynnmatt@jps.net>
>
> Chuck-
>
> It must be that since your engine and mine, they changed their
> thinking
> on jet needles, and sent mine with only one groove.
> I have all three float needles, and I concur with your reading of
> 1.5 oz
> on the "silver-springed" light needle. My "gold-springed" medium
> needle
> scales at between 4-5 oz, and my "black-springed" high needle is in
> the
> plane at this time, so I defer to your reading of 31 oz.
> The silver, gold, and black colors are what I observed, and are not
> "official" by Bing. They refer to the three needles as "float needle
> light" , "float needle medium", and "float needle heavy." I ended up
> with all three due to various fartings around with the carb. I'm
> pretty
> sure the number of my main (#220) conforms to the size etched on the
> carb, but as Andy said earlier.....
>
> "You may also be unaware that Jabiru went through a phase a few years
> back of drilling-out jets to achieve the required mixture, so what was
> stamped on the jet wasn't necessarily the size of the hole.....This
> was
> from memory on 2200s before the year 2000, or so, but ask your
> dealer as
> they have factory information (I'm afraid I don't at present). To
> compound the issues, my understanding is that the sizes stamped on
> main
> jets don't correspond to the jet diameter, but on needle jets they do!
> This means a 2.80 needle jet has a 2.80mm hole, but I'm pretty sure a
> 255 main jet isn't 2.55mm. I have no clue why this is."
>
> .....that number may or may not be of value.
>
>
> Lynn Matteson
> Grass Lake, Michigan
> Kitfox IV Speedster w/Jabiru 2200
> flying w/490+ hrs
>
>
> On Apr 28, 2008, at 10:15 AM, Chuck Deiterich wrote:
>
>> <cffd@pgrb.com>
>>
>> Lynn,
>>
>> I am sure I have a needle with several grooves.
>> When I replaced the float needle with one that has a stronger
>> built in
>
>> spring (black), I did not readjust the float. The spring in the old
>> needle (orange) would compress at 1.5 Oz, while the spring in new
>> needle takes 31 Oz to compress (yes 20 times more). This means that
>> any compression of the weaker spring would effectively have a higher
>> float level. Thus my float may be a bit low. The 255 main is larger
>> than what Jabiru now puts in the Bing. SB 18-1 says mine came with a
>> 250 but it did not, as the main jet size is scribed in the side of
>> the
>
>> carb body and on the jet itself. Lately they are using a 245 main
>> jet. Needle jet sizes can be misleading as the needles used are
>> different.
>>
>> Chuck D.
>>
>>
>>>
>>> Time: 04:47:22 PM PST US
>>> From: Lynn Matteson <lynnmatt@jps.net>
>>> Subject: Re: JabiruEngine-List: Float Level
>>>
>>>
>>> The Bing manual for the carb says NOT to change the float (from what
>>> they suggest) to cure a problem, but to cure the problem by
>>> addressing either the main, the needle jet or the jet needle,
>>> whichever "neighborhood" the problem resides in (my analogy). I've
>>> read of guys who have adjusted the float height, but Bing says not
>>> to. Are you sure you have a "lowerable needle"? Mine is not, having
>>> only one groove for the snap ring.
>>>
>>
>>
>>
>>
>>
>
>
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