Re: Posa idle adjustment

Marstalls <marstalls@...>

My experience with the Posa leads me to the following comments regarding
your situation.
1. Disconnect your linkage from the carburetor slide and see if it is
actually closing all the way. It will appear to be closed when it isn't.
Close the slide and see if your linkage hooks up with out moving the slide.
2. It sounds like your mixture is still too lean. If you enrichen the
mixture it will idle slower. That may also explain the lower static rpm.
3. DONT try to fly it with only 2700 rpm static. You need to see 2950+
4. I have found that I need to aggressively lean the mixture after engine
start to keep it from loading up and therefore hesitating when full throttle
is added. I keep it leaned until I push the power up for takeoff. I also
find that I need to lean it on long letdowns to keep it from loading up. If
I don't it will balk on touch and go's or a go around.
5. Also make sure you have the carb heat butterfly open when running it
up. Otherwise it will run rough and at a lower max rpm.

That's my 2 cents.
Jerry Marstall
Asheville, NC
Tri-Q2 187 hrs

----- Original Message -----
From: "jjq2flyboy" <jjflyboy@...>
To: <Q-LIST@...>
Sent: Sunday, December 23, 2001 11:14 PM
Subject: [Q-LIST] Posa idle adjustment

I am hoping those knowledgable about the posa carb as used on a
Revmaster 2100D might help me with this problem. I am having problems
getting the engine to idle below 1000 - 1100 RPM and have tried
adjusting the idle speed screw several times with no improvment. I
have researched the articles on this list pertaining to the posa and
noticed posts that mention possible problem ares such as the slide not
closing and the main needle requiring fileing and/or sanding. I did
think there was a problem with the throttle not closing all the way
when I found that a cotter pin at the bottom of the main throttle arm
shaft may have been contacting the cover for the main needle
adjustment at the bottom of the carb. I reversed it and pinched it
tighter but still have the problem. It may still be coming into
contact with that needle cover but it sure looks like it is closing
all the way. How big should the opening be at the bottom of the slide
when the throttle is fully closed? My posa is the simple one with no
float or idle mixture adjustment. Any help would be appreciated. The
plane moves along at a good clip with the engine running at 1000 RPM
and I feel this could be a serious problem when it comes time to do my
first landing, which I hope to do this week while the weather is
forcasted to be good here in Salem OR through next Thursday. But you
can never tell this time of the year in the Northwest. We just got
over many weeks of seeming endless rain. BTW, I did adjust the main
needle out one full turn after doing a full power runup as my CHT/EHT
were quite high (CHT was ~475 - 500 and the EGT was not behaving when
I did the test - although it seems OK now that I have cleaned the
connections at the back of the instrument). I was seeing 2600 -2700
RPM with full throttle. Someone on the list mentioned that the posa
doesn't like full power so perhaps I should try it again at 75% or so.
It also did seem to falter a bit while increasing the power, but this
did seem to improve after the oil temp got in the green.


Jerry Jerome

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