buildflycrash

Flying the mess out of my QQ Yak DA50. Up, down, inverted, hover, harrier, blender.
Also doing some Basic IMAC Hammer head, humpty bump, C8. Just having a ball.

Well if I fly the Basic Imac pattern I can get thru the whole thing then at the last manuver- 1 1/2 spin- My engine quits every time. DEADSTICK!

Lucky the spin is high and I can bring the plane around, line up, Land and roll out very close to perfect. (I've gotten good at it).

The engine has about 8 Gal. thru it. I think the high end is rich still becouse its popping and spuddering a bit and the response sometimes lags.
The low end I hate to touch again becouse the one time I did lean 1/16 turn I could tell it leans out and did die on an up line.

Why would this thing Die only on the spin? After doing other downlines perfectly?

pe reivers

I have a feeling, that the balance between idle needle and main needle is a bit off.
Richen the idle a bit (1/4 turn), and lean the high needle about 1/8th.
Does this also happen with a full tank? Your fuel pickup may run dry in certain manoeuvres (maneuvers). (manoeuvring UK, US maneuvering)

bubbagates

My Feedback: (32)

You sound as though you are too lean on the high end. If leaning out the low end causes the engine to lean out on the upline then the high end is too lean. Set both needles to 2 turns open, lean the high end until it reaches max then back off 200 rpm, now lean the low end until it will not transition then richen it until it just transitions nice and quick, recheck the high end, then go fly.

the other thing is the carb may be seeing weird pressure due to the round cowl of the Yak. What this will do is change the needle settings under certain flying conditions. there are two good ways to fix this. Take the plate off the carb and solder a small copper tube over the hole, being careful not to plug the hole, now reinstall the plate, connect a piece of fuel line to the copper tube and run it into the fuselage.

The other thing is TroyBuilt sells a CF cover plate that is designed to bolt right over the carb plate with the pressure hole that also works well.

If resetting the needles does not cure this then do the plate mod and reset the needles. At 8 gallons, that engine should be rock solid. Also what prop are you using?

buildflycrash

But Why can I do a humpty bump with a long down line with no problem and a short down spin kills it?[:@]

Its running fast on a H Bump up line and several seconds at idle before a spin.

High needle lean? The engine poping a spuddering it seems rich. Every time I turn it in 1/16 the engine seems better. Ive done almost 3/4 in from the origional setting. (not sure what that origional setting was.)

JoeAirPort

My Feedback: (41)

Easiest to try is a diaphragm vent draft block. Use a piece of pop can or whatever. That rules out a weird in-cowl turbulance caused by that manuever. The needles should not fix this issue since it's not an upline or any other that loads the engine heavily at high throttle settings. A spin is done at very low throttle right?

Did you get the carb update? The one that changes the pulse pickup location?

buildflycrash

The engine is New from DA less than 4 months.

Vent block with soda can- Is this how to??
--cut square same size as carb
--drill same pattern for screws
--remove screws and install metal "block" over side of carb
--Air can get around "block" but not so much
???????

bubbagates

My Feedback: (32)

This is exactly why we are recommending the vent hole fix. If it runs good on the ground but changes in the air and while doing certain maneuvers, the airflow through and inside the cowl is causing your problems.

I recommended verify the needle settings since a call to Da would result in the same suggestion.

My first Yak had a very similiar problem, my Cap did the exact same thing in KE in one direction only and in upright spins.

The soda can idea is another method that I forgot about but have seen a few times, mainly on DA100/150's especially since the carb if down at the bottom with the vent facing front in most cases.

JoeAirPort

My Feedback: (41)

That sounds about right. I used the bottom dome of the can to create a little aluminum bubble over the vent. I only drilled two holes since I thought that would be more than enough to hold it on (it is). I bent the two sides of the dome flat for the screw holes. Marked and drilled them and just fastened it to the front two holes. That's the side the vent is on my carb (top-front of carb). Make sure the dome overlaps in front to cover the vent. Mine turned out pretty nice, wish I had a pic for you but really it's pretty simple to do. Just make sure the vent can get air from the sides.

One thing I can say about these engines is there seems to be some issues with them flaming out at low throttle settings with the plane inverted: Inverted harrier, inverted flat spin, top of inside loop, bottom of outside loop. One theory is that the engine goes rich when the tank gets higher than the engine at very close to idle. I had a couple of friends flip my plane inverted with the engine running at idle. It did lose some RPM's. Then I told them to pitch it forward and down. it almost quit but recovered. So apparently the low end is sensitive to the tank or engine attitude. In your case the plane is still upright so it's not the same exact conditions that mine had problems with.

I'd make sure your electrical connections to your ignition are sound. Move the wires around when the plane is running. See if you can get the engine to quit or sputter. Move the wires where they connect to the switch. It could be that your high G spins are moving the wires around and worsening an already bad connection somewhere.

bubbagates

My Feedback: (32)

Joe,

If you are having this problem, give DA a call with the engines serial number. There is an update that was applied a while ago that takes care of this and all updates are free of cost except for shipping and the turnaround is usually really quick. In my case I bought one of my DA50's used and told them that and they still did the updates for free and I sent it overnight from PA on a Monday and got it back the next Monday only because they sent it ground. They did however call me that Wednesday to say it was done.

If I remember correctly, it had something to do with raw fuel pooling in the block the reed valves are in. Tank position does not matter on a gas engine since they use a pump and it only pumps when the pump side of the carb receieves pressure pulses from the engine. That's why you can use a "T" in the carb/tank line to fuel without any worry of the engine flooding before you start it

DA can tell you if the engine has been updated as long as you can supply the serial number. There is actually 2 or 3 updates, one also involves something with the crank/piston area but again I'm having tons of senior moments today so my memory is usually the first to go

JoeAirPort

My Feedback: (41)

Bill,

The updates are all in this one since it was new enough. I did call DA about it and they said it was the in-cowl turbulants. Did the pop can mod and no change. Also tried another carb and no change. I plan on sending it in but not until late November when my flying season ends. I can still fly, I just know what manuevers to avoid. When I enter a blender I keep the RPM's high enough where it won't flame out.

Back to the original thread, DA will recommend the stock carb settings which are around 2 high and 1 7/8 low (Used to be 1 7/8 H, 1 5/8 low). What works the best on mine is 1 7/8 high and 1 1/16 low. DA says it's way too lean on the low needle but that's the only way it'll run without being stumbly rich on the transition (and gobble fuel). They want me to send it in, which I plan on doing eventually. Discounting the "inverted at idle issue" mine runs like a champ. Lightening fast transition, and lots of power.

bubbagates

My Feedback: (32)

I actually setup an idle up switch on mine. What I do is start and takeoff normally (switch is off), then once I am ready I hit the switch. On my 10X I have it on the mix switch with the left hand knob setup to adjust the idle as needed. I also setup the same switch to allow 2% down elevator when at idle to help with my downlines being straight down. I long downline for IMAC I set the idle a bit lower on the idle up switch using the knob, for Blenders I leave the idle slightly higher. That way I get no flameouts. I do turn the switch off for landings unless I am going into a strong head/cross wind then right before touchdown I turn it off and the plane just lands nice and sweet as could be

I had it happen once and that's when I did the switch thing

Tired Old Man

My Feedback: (1)

I had the same issue in a plane with an engine by a different manufacturer. I did the diaphram cover trick and a bunch of other stuff. Ended up that after I placed a heavier weight on the clunk of the pick up line, added a piece of brass tubing to the middle of the line to assure that it not fold up and get stuck in the front of the tank, and made sure the vent line could not get pinched off via centrifigal force, the problem went away. Only happened in Blenders and inverted flat spins. For a period of time I only did Blenders and the like when I was about finished with that flying session since I knew a landing would be mandatory immediately after the maneuver.

JoeAirPort

My Feedback: (41)

Funny you mentioned this. I actually had a paragraph in one of my previous posts about exactly what you said but deleted it thinking it can't be the problem since the fuel left in the clunk line shoud be enough to keep the engine running. I think I will re-plumb my tank using that black Hayes (pick your brand) neoprene tubing. That extra brass tubing in the clunk line is mandatory, I tested it without on a tank and the clunk flopped right to the front of the tank when I turned it upside down. I think I will do this mod ASAP.

Tired Old Man

My Feedback: (1)

An item that makes an excellent heavy clunk and filters the gas at the same time is the stock Walbro internal gas pick-up/filter. The Walbro part number is 125-527.

I don't have anything for internet access but the manufacturing division is: Walbro Engine Management, Aftermarket Division, Cass City, MI 48726

That should be more than enough for any small engine shop to come up with one or three.

Josey Wales

My Feedback: (61)

Ive been using the Hayes neoprene without any added brass and havent had any problems..However after the season when I change out the lines, I think I may add a piece as suggested for good measure..Maybe because Im using a 3 line system the extra clunk helps keep the main clunk towards the back of the tank..

BaldEagel

Reading your orriginal submission I tend towards Silversurfer's interpretation of your problem, if this happens at the end of a flying sequence in the spin then it seems to me to be a centrafugal problem, try the spin at the beginning of your flying sesion and see if it happens if not then its a tank or fuel pick up problem, put a heavier weight on the clunk before going all the other routes its the easy solution first.

Mike

MustangFan

I have the same Plane/Engine combination ... and had the same exact problem.
My problem turned out to be the clunk ... it was too far to the rear of the tank ... moved it forward at least a half inch ... problem went away.

Talked with a friend with the same engine and different YAK ... he has his clunk forward also ... said it works better for him in aerobatic maneuvers.

Just a thought !

buildflycrash

Maybe a lot more than "Just a Thought". Sounds like the best place to start. I'll do the soda can vent block also. That vent thing seems a problem on more than a few DA's.

Now this is the beauty of RCU...same plane/engine...exact same problem...and a solution

JoeAirPort

My Feedback: (41)

I tested my clunk by rotating my fuse with the canopy off, the clunk moves very freely and there's no need to re-plumb it.

My engine tunes very weird. I was at the field today playing with the needles (again). The high speed needle does nothing to the full throttle RPM's. You can turn it and turn it and they don't change. I stopped closing it near one turn. So I just put it back at 1 7/8, then turned the low end to near one turn out. That's where it wants to be to get that 4-stroking out of the mid-range. In fact I think it's at around 7/8 on the low, it's way in (and runs great). This is my second carb on this engine. The first one liked 1 7/8 on the high and 1 1/16 on the low. I bought the 2nd carb thinking the first one was bad. DA said if the carb was bad they'd credit me if I sent the bad one back. Either something's wrong with my engine or this is what the needles are supposed to be set at. It runs awesome, but not being able to tune the WOT with the high needles bugs me. What the hell is it for? BTW, I am sending this engine in after the flying season. Another thing, I'm only getting 7000-7100 on a Menz 22x8 on the new carb and used to get 7200-7300 on the old one. Guess which carb is going back on the engine? The old one.

DA said that my low end should not be so lean. I tell ya I don't know what to think anymore. This is my first gas engine.

Josey Wales

My Feedback: (61)

Joe..I went thru the same stuff like you with my first 50..What I do now is just leave the high needle alone and tune the low first..then Ill check the high by leaning until the rpm changes then back it off..If I cant get a change by leaning, I just richen it until the rpms drop then lean it out until the r's pick up again..Of course then you need to go back to the low and make any minor adjustments but most of the time its very close..Then Ill just fly and make any other necessary adjustments ever since I started tuning it this way I havent had any problems..the only time I need to mess with the low end is if the humidity is high..other than that I havent had to touch the high needle all summer..

bubbagates

My Feedback: (32)

Joe,

Check the little pulse line running from the reed block to the carb. I had a similiar problem. Mine ran great for 70 some flights and then one day, dead stick. I landed it, walked out to it and started it back up to taxi back and could not get above 2 or 3 clicks before it would try to stop.

I took the carb apart at the field and cleaned it out as I did find some crap in the screen. Still would not transistion well but it was better. So on a whim I replaced the pulse line and it's right back to making great power and being able to richen or lean the high speed. Now I caused this problem. I had flipped the carb to account for the way I had the servos setup so that put that line up against the base of the head so it must have rubbed a very small hole in it.

After some thinking I realized that the previous 5 or so flights the engine was not making full power like it used to but it had gotten humid so that is what I thought was causing my problem. The day this all happened, it was just as humid but after the "fix" it ran like it used to do.

My point is, check for an air leak and replace that line

srm99

SOUNDS LIKE YOUR IDAL IS TOO LOW WHAT RPM ARE U RUNNING AT IDAL WHEN WARM
as my da when i start idal is higher than when warm when warm idal drops 300 rpm now if u tuned when cold this is the problem u are saying
now it has nothing to do with carb plate so dont wast your time .

if anything other than idal is that your reed valves are getting stiff and is struggling to get fuel in a high g move
now this is a new motor \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\SEND IT TO DA /////////////////////////////////////////////// AS if u touch it u can loose your warrenty

my da i have a idal speed and when i take off i up the trim by 3 nocks on the trannie and i have never had a dead stick on any moves stall turns the lot i even trust me da dod (down On The Deck) so speak to da they know all the fixes for all the problem .