bob_nj

My Feedback: (62)

The engine has 5 gallons of lawnboy so far.
Runs ok, but I can't get it stop leaning and speeding up while inverted.

I've read several threads and tried the following;

Vented the carb inside the fuse
Vented the carb outside the fuse
Vented the carb to a balsa box
Added another pulse port to reed block
Used 23x8 in place of the 22x8
Replaced the reed block gasket where it meets the head.

Does this go away as more fuel is run through the engine?
I'm hoping it will, but can't see why it would matter.

This makes some maneuvers like rolling circles, and nice slow rolls almost impossible.

Any ideas?

Thanks
Bob

Tired Old Man

My Feedback: (1)

You've independantly discovered why many prefer Taurus, the old Brisons, Zenoah, and Brillelli. You can get close with what you have, but that's all.

Josey Wales

My Feedback: (61)

Carroll-RCU

My Feedback: (43)

Pat, I think the guy was looking for help on his DA 50 problem, not about other brands that maybe you prefer.
Cheers!
Carroll

Jake Ruddy

My Feedback: (40)

I think Pat is saying there isn't help - this is a common problem there must be 50+ threads where this is discussed and rarely is it solved.

In fact there is someone at my field going through the exact same issues...

Carroll-RCU

My Feedback: (43)

Yea I've read about this issue in the past. I've had 5 DA 50's and they all ran great at any and all attitudes. I don't know what may be causing the Inverted transition other than maybe a stuck clunk in the tank that may be sucking air when Inverted. I do hope he finds the problem and can shed some light with others that are having the same Issues with the DA 50.

Pat seems to always have good replies and I generally trust a lot of his advice.
Carroll

karolh

I second that statement.

Karol

bob_nj

My Feedback: (62)

Tank lines are newly replaced and are in good shape.

How does the motor even know the plane is inverted?
Does it have something to do with the fact that the motor is installed inverted?
Would the reeds cause someting like this?

Thanks for the thoughts so far though.

So many questions...

Carroll-RCU

My Feedback: (43)

My thoughts: If the clunk is hitting or rubbing the back of the tank, could this possibly get stuck in the lower to mid section of the back of the tank and when inverted the clunk starts sucking some air which would cause the engine to go lean and the rpm's would Increase. This is just a possible cause. This is just a thought and may have no merit at all, but something to think about.
Carroll

karolh

This just seems to be a quirk that is commom to DA's. Some do and some don't.

Karol

pilot727

If your fuel line is to long the clunk will suck up against the rear of the tank and will not get any fuel as carroll has said. It has to be perfect.

bob_nj

My Feedback: (62)

I'll double recheck the fuel lines.
Good thought, although it did this even before I recently replaced the lines.

Let you know tomorrow

Bob

Jaketab

My Feedback: (2)

My DA does the same thing. Have also followed the threads on this subject. One possible cause, (maybe off base - untested) is that air entering the tank through the vent tube meets less resistance when the plane is right side up. The vent tube is vented directly to the atmosphere. When the plane is inverted, the vent tube has to draw air into the tank while traveling through the fuel reserve. This in turn could put more pull on the carb pump and lean the mixture. At this point, air is more likely to be drawn into the engine through a weak point in a gasket or fuel line.

If this were the case, and I don't know that it is, the fix could be as simple as installing a clunk line on the vent tube so that the fuel draw pressure would remain more equal.

Has anyone tried this?

Jaketab

pilot727

Hi
An idea with the vent tube after i bend it, i use a round spring that looks like it come from a spring door and you put the tube in it and bend it with any crimps in the tube, they are all made different sizes, also at the end of my vent tube i always put a piece of fuel line about an inch long, that way it will hit the top of your tank, cant get it any closer then that, i have never had a problem with any on my tubes doing it that way

arobatx

If the pulse port, diaphragm, metering lever....etc is functioning correctly, the carb will pump gas several feet straight up without hesitation, pulling the air through gas when inverted should have no affect, similarly. Perhaps the design of the reed block allows for fuel to flow through the case efficiently when the engine is inverted, and upon turning it, the fuel begins to puddle instead...leaning it. And you burble, go lean, burble go lean, as you do your slow rolls....I dunno...but I would figure by now, with all of the complaints, and the high level of customer service DA owners acclaim...it would be solved.

outssider

My Feedback: (23)

my tank is 6 inches lower than the carb. When i go inverted the mixture richens a "tad". Doesn't effect performance though.

plasticman

My Feedback: (97)

Bob,

If you decide to continue troubleshooting here is what I would do:

1. Buy a new walbro carb from Scott at brillelli.com
2. Replace the reed block.

You should not have to do any of this, I know, but these two items fixed my brothers DA-50 with the same problem. We tried all the "magic solutions" but this was the only thing that worked. Really, the carb replacement was the primary fix.

David.

Carroll-RCU

My Feedback: (43)

Bob,
I talked to a good friend that I buy all my plane accesories from and he gave some things to look for that may be causing your problem.
1. Check your brass vent line inside your tank to make sure it's not too close to the top of the tank if it has a curve to it. This could block the vent when inverted.
2. Clunk should be at least 1/2 an inch from back of tank for proper fuel flow.
3. Cowl opening should be a 1 to 3 ratio for proper air flow, air flow changes when Inverted.
4. Does your DA have the upgrades?
These are just suggestions that are worth looking into, I'm in no way an engine expert but have listened to a lot of those that have a lot of experience in this hobby.
Have you contacted DA about this, they would be the ones that could shed some light on this?
Carroll

bob_nj

My Feedback: (62)

My engine does have the upgrades.
DA said that richening the engine has solved this for others.
I'm waiting on a reply as to which needle to richen, as the midrange is already rich.

plasticman -> What was the carb model/number that worked for your friend?

Thanks all
Bob

Panzlflyer

My Feedback: (15)

To lean on the low end...mine did it until richen'd up 1/8, seen several other do it as well.
Burble can be got rid of when its finished running in.

kfir2

Had a similar problem with a 3w 50 had been ok for years and no one came up with an explantion. this motor would die when rolling under 4000 rpm even on the ground> After much head scratching and queries at a show Ian Nicol of iadmodeldesigns.co.uk the zdz agent said not an uncommon problem and is to do with the metering valve setting I reset the valve lever flush with the body and this made a diffenrence to the inverted running. After have lost 2 models to this fault and not wanting to lose another, having proved that it made a difference, and knowing that the tillitson carb had, had a large quantity of fuel through it and the valve seat must be suspect, to suddenly have changed, a new carb (Walbro from da 50) was fitted problem solved. The logic is supposed to be that when rotated the weight of the needle changes from pressing down on seat to falling off of seat or vice versa depending on orientation of carb. Dont know if this will be your answer but is the best I have to offer.

bob_nj

My Feedback: (62)

Panzlflyer -> I,m on my 5th gallon. Maybe it will just take time?

kfir2 -> I have the Walbro tool kit and did set the valve lever to the correct height.
The pop off pressure was excessive I thought at 24 pounds, and brought it down to about 14.

We'll see...

Tired Old Man

My Feedback: (1)

Many have had this problem with the DA-50. The primary difference between the DA-50 and the DL-50 are the parts that cause the problem. The DL does not have this problem due to the change in parts. Those parts are the reed valve and the carb. It's that simple.

From a personal position I think the DA-50 is a wonderful engine and has a lot of potential for even more power than it has now. Change those two parts and you have a nearly bulletproof engine with a lot of power and the best customer service department and support system in the business. I would have several of them if it was not for the common burbal, rich mid-range issues. When I hover I want to be able to hit the throttle, see an instant upwards jump, and hear a steady increase in rpm from start to finish. Same with a low, high alpha KE pass. I hate hiccups, especailly in an engine. They make me fly a lot higher than I want to.

It's not about personal preferences, it's about what works best. At least for me. I don't give a hoot who makes it if it works great, DA, 3W, ZDZ, Brillelli, Taurus, BME, Mintor, etc. Brand names don't matter when they do it right.

Josey Wales

My Feedback: (61)

This is what I would do IF I still had both my 50's--

bob_nj

My Feedback: (62)

Pat -> What's special about a DL50 reed valve?
Will it work in a DA?

Will the reed block fit a DA?