[sm=punching.gif] All rightt!! I was waitin' for this to start up

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Oh come on now. [sm=lol.gif]

Come on now Champ, were in your corner.

Oh I now, it's funny how we all end up in the same thread. Same results. We're having fun with it.

Just a quick update...
The engine is now running a lot better with very little to no change in RPM between upright, knife edge or inverted.
I have half covered the approx 8mm hole that I made in the box behind the firewall with tape to see if this makes any difference.
I still have an issue with it when its in the prop hang though. It just wont settle down. Its either up or down surging or dying. Almost as if its coming on and off the pipes ( Mufflers )
Any ideas???????
Thanks for all your help guys.
Regards Al

No ideas???
Oh well, I guess if I were to ask if ZDZ's are better than DA I would get a response. LOL

We all know that ZDZ's are better than DA's. That's a given.[sm=lol.gif] I would take advantage of that great service DA is known for and send it in.

Exactly same thing happend to me. Same model, same engine, same maneover and same final result.

In my oppinion, there are two differente problems. First is the "pressures difference" problem that can affect any gas engine, and the solutions, not always sure, are those which you have described before. Sooner o later, with the balsa box, moving the line or mounting a veloctty stack, you will find a solution, sure.

But, and this is harder to say, in my experice, there is other problem regarding DA 50 R. I don't want to extrapolate what I have seen to the rest of the world, but I'll tell you what I have seen, and this is fact. In my club there are 10 DA-50R which belongs to 6 different blokes. Those engines have been runing-in in different ways, flown in differente models like CH Vision, QQ 86", Extreme Flight YAK 54, Funtana, GP Yak 54 ....etc.

The fact: ALL OF THEM run richer during the inverted flight than in normal flight at iddle of medium gas. Even if the pland is not flying. You can hold the plane whit some helpers an see it. At least 500 rpm of difference. We have tested everythig related to the pressure reference. It has worked for MVVS, but nobody found any difference with DA-50.

I crashed and totally destroy my QQ 86" after only 12 flights when the DA50 sudenly stoped in an inverted harrier at 2 m height. I was so angry that I tried to investigate and test whaterver coul be a solution, and, at the end, I found it. The complete solution. I sold both DA's and bought two marvelous MVVS 45. Those engines run great since the beggining with no issues.
Now, a group of us have bought 4 C-Arf 2.12 Extras and we are using MVVS 45 for this planes, except one, that still mount the DA (and still having the same inverted issues)

Reading the Walbro service manual troblesouting section you can find a explanation of this problem. In short, and generally speakin, it comes to say "a defficient inner design of the crankcase may cause fuel inside not to be gaseous but fluid. By turnning the engine up or down, may couse this staff comming in to the cylinder and making the mixture richer" and I do belive this is what happend with DA.

I only want to add that this 10 DA's have beingn bought not at the same time, but for a couple of years, from different distribuitors, and it's not a question of carb since DA-50 and MVVS 43 wear exactly same walbro part number carb.

On my part, I never would buy a DA again.

Sorry for this long letter and excuseme if my English is not good enougt.

Best Regards,
Javier

Al,

I'm running a DA100 with stock mufflers in a 33% H9 Extra. The 100 will be a bit rich in the midrange no matter how you set the needles....Mine has never died in over 50 gallons. When I hover the 33%, I tend to be in that "rich" spot sometimes. With a light airframe, it just can't be helped. I'm hovering/TR'ing at 1/3 throttle or so. A higher loaded prop helps eliminate some of the burble in that spot. Pull your plugs and see if you're running a bit rich. If so, leaning the high needle will help smooth it out a bit. What size prop are your running? On a 26x10, the burble will be more noticeable than on a 27x10.

Ditto on the DA50's boy's. Had two of those things and gave up on them before they cost me an airframe.......Tried everything mentioned here....IMO the fuel is puddling when at low rpm and inverted......No way could I do inverted harriers with mine. A Ralph Cunningham G62 solved my problems. Now if all you do is fly IMAC type maneuvers and stay on the throttle, the engines run fine....Sounds like crap though.[:@] rattle, rattle.........

Hey guys... I realize this is for the DA 100 but I have a couple of questions for my DA50.

For that fix where the pipe is in front of the inlet of the carb... how is it attached? Mrbigg posted 3 great pictures but for some reason when I click on them they don't go to a large size.

My DA 50 tends to run slightly rich when the aircraft is rightside (engine inverted) at less then half throttle, but when I roll inverted it actually leans out a bit. (and sounds way better I might add - nice and smooth) Why can't it always just run like this??!!!!!!

Also, when I pull up on the elevator hard (positive g's) when the engine is at or near idle the engine suddenly slows down and sounds like it's going to stall.

Is this a "g" loading problem or a airflow/airpressure problem within the cowl? (I should add that at this point I have the static air pressure line going into the fuselage and the firewall is virtually sealed other then small holes for the throttle and choke push rod) I can see that with the openning on the bottom and pulling up there would be more airflow in through the bottom and therefore more pressure. What is the relationship between the pressure for the static air source and the other side of that diaphram??

Finally... does anyone know if the DA85 does this? Looking at the numbers (horsepower versus weight) it looks the best in it's class... but if it's going to run this way I would be inclined to buy something that runs more smooth.

Oh... one more point...how about these carbs that are mounted on the bottom as opposed to the back...does that solve the problem?

Thanks for your comments,

Chris

Chris,

I dug this out of my files........I've also heard of some guys using JB weld to attach the brass tubing to the cover.


Here are the pics for the diaphragm mod. Not hard to do.....

1. Remove cover from carb.

2. You may need to drill out the hole a bit larger. I made my hole just a bit smaller than the tubing. That way you can just set the tubing on top of the cover and solder. I believe I also cut like a 30 degree angle on the tubing to help get the angle I needed. Also on one of my carbs the original hole was on the edge of the cover. I filled this one with solder and drilled a new one in the center. Just seemed like it would be easier to solder the tubing on that way.....

3. Use a dremel cut off wheel to ruff up the metal a bit. Clean well with alcohol.

4. Bend brass tubing. You can use 1/8" or 3/16".

5. I used the Butane torch you see in the pic. Works real well. I just used regular electrical solder. You can use silver solder if you like. Add some flux to it before soldering if you have it. If not, there is probably enough flux in the solder to do the job. Just make sure everything is clean. Wouldn't hurt to take some steel wool to the end of the tubing your soldering also....Clean afterwards.. You can see how I used a small vise & holder to make the soldering easier.

6. After you solder the brass tubing on, be sure the inside of the cover is smooth. Any burrs will poke a hole in the diaphragm.

For some reason I can't get the pictures uploaded. [:@] I'll keep trying.

There, I finally got them uploaded.......

Hi Frank...

First off... thanks for your help with this... it's very much appreciated.

So do you have a piece of tygon on that brass pipe that is bent down towards the inlet of the carb? If so, how far away from the inlet is it? I'm using 3" stand-offs. Should I just run it around to between the firewall and the carb inlet and attach it to the firewall?

Thanks,

Chris

Chris,

I believe someone else in this thread mentioned it, but the best thing to do is glue up a small balsa box maybe 1"x 1" or 1 1/2 x 1 1/2 out of 1/16 or 3/32 balsa. Mount this box in the fuselage, and run a piece of tubing from the brass pipe to the box. No need to drill any extra holes in the box. The balsa will "breath" enough for the diaphragm in the carb to work properly. Make the fit snug where the tubing goes into the box.