DA 100-Anyone know what is happening?

[3Dkid330]

Hi everyone,

I have recently been trying to get my QQ Yak trimmed, 25 flights on the airplane, getting the KE mixing closer to being dialed in. I was going to do a demo this Sunday at our club's Family Fun Day event, which is aimed to introduce the hobby to new people. (demos and allowing the public to come in to fly on a buddybox trainer airplane)

Anyway, I have done demos before, so I knew that this one would be no problem, but I really wanted to get the mixing dialed before flying it there, so we took it to the field today. Fired it up, warmed it up a little and range checked. After holding the power at a little bit above idle and then powering back up, the engine immediately flamed out through the transition. Thought it might have loaded up, so we tried it again and again with the same result. Tried re-tuning and richening it to no avail, besides, I have had 25 flights with the engine flawlessly running, not one sign of quitting, never touched the mixtures. (I probably should have left it, I was pretty sure it was not the settings)

So, took everything apart, cowl off; checked the throttle servo, it was good; checked the fuel line for leaks of bubbles, it was also good, which rules out a tank problem.

In the past few flights, the top end power seemed to be a little bit less than it used to be, and the throttle response pulling out of one maneuver was a little weird. Runups on the ground today were also ripping the heck out of a Menz 27x10 on the ground at full power, and the cylinder heads are somewhat pink, pointing to a lean condition.

The only thing I can think of is that something in the carb is clogged, causing the lean situation, the pink cylinder heads, and the prop ripping on the ground. (Makes sense too, good fuel to the carb, clog in the carb, not enough fuel to transition quickly without bogging and quitting, restricted fuel flow causing the lean top end resulting in the overheating (prop rip while it is still cool)

We pulled out a little screen that was inside the back of the carb, there was some stuff on it, but when reinstalled clean, same result. I am thinking that this means I will have to tear down the carb, but I do not know my way around these things. I am thinking it is the carb, but I could be wrong. What do you guys think?

I am not bashing on DA or anything at all, Just trying to find a solution to a problem.
(It's been an awesome engine so far)

Thanks,
Brandon Kontorinis

[The Hobbyman]

Are you sure your'e tank stopper is a gas one and not a glow one, if it is a glow one the rubber will slowly decompose and deposit itself in your'e carb ?

[notorious_benny]

Is there a filter between your tank and your carb?? When mine got full of crap it wouldnt transition to well..... cleaned it out and it runs like a dream.

[TheTank]

Ignition batteries low? If you are using the "power poles" connectors that come on the ignition (red and black), check to make sure one of the leads isnt broken. Sometimes they are crimped to tight, and cause the wire to break, it stays in contact with the metal, but results in low ignition voltage and sometime intermittant firing or dropping of one or both cylinders. Just some ideas.

[Tailwind]

Hi,
Also check the two mount bolts for the carb. I had the same exact problem with a DA50, one day fine the next lean. I found both carb mount bolts had loosened up. To be safe I checked mine on my DA100 and they were fine.
Dom

[WTF]

Can also try backing out the low speed mixture screw and then resetting it. Could be something caught in it, backing it out then resetting will get it out of there. This has work for me anyway on similiar problem.

[Vic3D]

Why are all DA's giving problems now?


B, like Tank said, it might be that power pole connector. The wires are not soldered to it, but crimped, you might have a broken or loose connection. You might have some crap in the carb screen though so you might wanna check the carb too.

My friend's DA-100 was giving problems during a long vertical line, it would start bogging while vertical, and after fooling around with the needles so much, I'm thinking it's an ignition problem, probably the power pole connector as culprit. Good luck.

Vic

[MrKiwi]

It might even be to rich, i've had a problem were i leave it at idle too long (6 seconds) and as u advance throttle the fuel actually cools the engine down and makes it quit. but thats just 0.02

[todhog]

	Quote: Originally Posted by TheTank
	Ignition batteries low? If you are using the "power poles" connectors that come on the ignition (red and black), check to make sure one of the leads isnt broken. Sometimes they are crimped to tight, and cause the wire to break, it stays in contact with the metal, but results in low ignition voltage and sometime intermittant firing or dropping of one or both cylinders. Just some ideas.

This is exactly what happened to me, the red wire was broken at the crimp. Cost me a couple of props.

Todd

[3Dkid330]

Thanks for all the responses guys!

Hobbyman, that is true, that or something else disintegrating in the fuel system may have clogged it.

Benny, I do not think I have any filters in the airplane, but there is one inside the gas tank (Jersey Modeler) that we use to fill up and defuel the airplane with.

WTF, My dad pulled out the high and low end screws, and found a tiny little piece of plastic inside the high, could possibly be what is causing it, but still not sure until it runs. Will go run it again today to see if that cures it.

Tank, before and after starting we checked the ignition batteries, both were above 7.0 with load which is good. I am using the Power Poles, that sounds like it could be the prob, if the piece of plastic found inside the high needle valve isn't the cause, we will most likely look there next.

Dom, Just went downstairs to check those two bolts, they seemed to still be nice and tight, I went over some of the other carb bolts just to be sure also.

Vic, I will definitely check the PowerPoles if I do not find the plastic in the high screw to be the cause. We checked the screen that you find in the back of the carb, cleaned it off, but still had the same thing. (I don't know if there are any other screens inside it, if there are, these might be something to check)

Armon, that is what I thought it might have been at first, but it did not load up when it quit like it had too much fuel, it just quit like it did not have enough fuel.

Todd, the connector seems like it can cause some problems, so if everything else does not work, we will check them definitely.

Thanks,
Brandon

[DKnippen]

The tiny piece of plastic is probably your problem.( I hope? ) Once these engines are set the only change they may need with the needles is when the seasons change if your in that sort of climate. When was the last time you adjusted the carb for your Lawn Mower??? never! If for any reason you have to start messing with the needles something else is wrong and that won't fix it. If the engine is getting lean because of the plastic It will overhest and quit.

[3Dkid330]

DKnippen,

You have a good point! I just went out to the field today to run it up, turns out the plastic that my Dad had found in the carb was indeed causing the midrange quitting problems and the overheating. Since we tried to retune it, the settings had to be completely redone from scratch. (took from about 3:40 until 7:40, then went to a friends house, just got back)

Seems to be running good now, but I can only tell in the morning early before the event, so I will be getting up early to get out there and fly it a few times to be sure that it is safe.

Thanks for all the help!

Brandon