DA-100 mixture adjustment?
 

Hello All,
I have been flying my DA for almost 8 or 10 gallons now and have never even looked at it since I installed it. I've never touched the needles as it's been pretty good. I've noticed lately that it seem to be a little rich in the mid range (at least that's my diagnosis). I get a little "smoke" when I punch the gas on the runway and the mid range is not as crisp as it once was.
With the excellent track record of this motor I'm afraid to touch it for fear I'll hump it up. I'm tempted to give the low needle a tweek but I donno. I don't want to send it back and have to wait a month or two for them to adjust it - can I do this on my own? I'm not even sure wich needle it is. Anyone have any comments for diagnosis and adjustments they can lend?
RickP

RE: DA-100 mixture adjustment?
 

Sounds like the low needle needs to be turned in a bit, you can turn it in till the engine bogs or refuses to take throttle when you open the throttle full from idle.

RE: DA-100 mixture adjustment?
 

Rick

It's not rocket science. Check the needles... Gassers DON'T smoke or shouldn't smoke... It's bad for their health, go figure!

Check your manual for the correct settings initial or give the guys at Desert Aircarft a call for the skinny.

The needles are identified on the carb body adjacent to the needles. BUT the LOW needle is closet to the engine center line.

Just to know where your at run them down (CW) to a light stop recording where you started at
by noting the revolutions or fraction thereof. This will give you a baseline.

It does sound like it maybe a little rich. Any hesitation or lazy transition? Will it idle forever?

RE: DA-100 mixture adjustment?
 

Rick,

It's not hard to do.
Start with the low needle( it's the one closest to the engine on the carb)
Turn it in 1/8 at a time and see what that does to your transition from idle.
On mine when it's cold it doesn't take throtle and feels very lean.
When it warms up after a minute or so it takes throttle with no hesitation.
Leaner than that and it won't start, richer than that and it will have rough transition after
long periods or idling.

You set the high needle for max rpms and then back it out a little.

It might be a good idea to have someone more experienced help you out while you
are doing this for the first time. All you need is patience, a flat screwdriver, and a tach.

Take care,

Stratos.-

RE: DA-100 mixture adjustment?
 

Rick, I agree, give the low end just a tiny tweak and youll be in business, you wont mess it up.

RE: DA-100 mixture adjustment?
 

Okay,
Pulled the cowel off last night just to have a look, gave the low end 1/8 turn, we'll see what that does. The plane will idle forever, just get a quick puff when taking off and transition is slightly rough. First time I touched the motor in over a year not bad ;)
RickP

RE: DA-100 mixture adjustment?
 

Hi Rick,

I am not trying to scare you here, and let me say all of the previous post are correct, you have nothing to fear. One thing no one has mentioned is, when you have your engine close to being tuned optimally, (which it sounds like yours is) small tweaks of the needles go a long ways. 1/8th Turn might put you on the other side of where you are at. When you are really close, 1/32nd can sometimes be all that is needed. Let me restate you have nothing to fear get the tach out and if you don't like your results turn it back to where you had it.

Kurt Cook
Fromeco Scale Avionics LLC
www.fromeco.org

RE: DA-100 mixture adjustment?
 

Kurt,
Thanks, that's just what I am afraid of LOL. I hear you. I put 1/8 in ready to take some out on a moments notice. No dead sitcks...
[sm=bananahead.gif]
Thanks
RickP

RE: DA-100 mixture adjustment?
 

Well,
That 1/8 seemed to make things better and added a ton of power overall. However, when cold and at idle it is definatly lean on the mid range needle; when it's warmed up its fine. Should I leave it alone or come back out a hair?
RickP

RE: DA-100 mixture adjustment?
 

Your setting is very close, fly it like that for a bit and if you notice any hesitation going to full throttle while flying then go a bit richer on the low needle.

flierbk

RE: DA-100 mixture adjustment?
 

I can't get my DA-100 to perform well in the air AND not be lean at start-up, at least not when it's below 80 degrees outside.
For the best in-air performance, I manage the lean cold running via a choke servo. I start the motor with the choke 3/4 of the
way closed. I slowly open the choke as I taxi out. By the time I'm ready for takeoff the engine is warm and the choke is
fully open.

I used to have a Brison 6.4 and it was the same way. I had to start it at half choke below 80 degrees if I wanted the mixture
to be just right in the air.

RE: DA-100 mixture adjustment?
 

Barry,
It was 30 degrees so who the heck knows LOL. I will try again this weekend and see how I like it. In air performance really came alive (I also tweeked my throttle curve so that may have been part of it). I didn't think it could get any better. Jury is still out - We will see monday.
RickP

RE: DA-100 mixture adjustment?
 

Say Rick,
What I did last weekend was install a fuel dot inline with my carb on the cowl. This allows access to both high and low needles via the fuel dot hole, and the dot covers the hole cleanly when done.

I too live in a rather high humidity area like you, so I figured I needed to do a minor tweek a time or two every season.
DA makes a very nice low profile fuel dot with the letters DA machined into the dot...very cool.
I know gassers don't usually require much adjustment, but I didn't want to have to remove the cowl every time I needed to.

Just a thought, good luck.

RE: DA-100 mixture adjustment?
 

My DA100 deadsticked on me today....it hesitates sometimes on the midrange...I think it is rich on the high..but this is my first gasser...it leaves some residue on the bottom of the plane...how should i adjust it??

RE: DA-100 mixture adjustment?
 

Rick,
Your engine is doing just fine. As it breaks in MORE and MORE, it will need to be slightly leaned out MORE and MORE.
Every DA I've owned has done exactly this. It is especially noticeable when it comes off lawnboy ashless for the first time, and onto Amsoil.
As stated above, adjust the needles in 1/16" increments. 1/8" is a little much when you are already close.
CDignition,
Leaving residue on the bottom of the plane is perfectly normal, ESPECIALLY when they are new. When they are new, they should leave BLACK residue on the plane. This is tiny bits of metal from breaking in.

barryBRCU,
If you can't get your engine to perform and not be lean, then richen her up!
I'm not trying to tell you that you are wrong here, but I guarantee that should not have to be slowly choking a DA100 as you taxi down the runway!
If you have tried messing with the needles, and still have the problem, call DA! They'll fix that thing. Are you letting your engine warm up real good?