Thanks jongurley for the flight report
I just added the balsa box to my new never run DA 50 in a DP Edge 540.

Who came up with this?

Maybe DA should start including the boxes with the engines.............

HERES A QUESTION FOR ALL OF YA WHY ONLY 5% ARE HAVING THIS PROBLEM THERE MUST BE ANOTHER SIMPLER ANSWER MAYBE A FAULTY CARBI MAYBE A FAULTY FUEL SYSTEM MAYBE A FAULTY CDI .
NOW TO AIR PRESSURE ON CARB PLATE IS A HOLE LOAD OF Sh%^ THE PRESSURE NEADED TO AFFECT THIS WOULD NEED TO BE 10BAR IF THAT WAS ACHEIEVED YOUR OUT FLOW ON YOUR COWEL IS NOT ENOUGH .
TRY YOUR PLANE WITHOUT YOUR COWL AND IF YOU HAVE THE SAME PROB DONT BLAME THE DIRAFRAM
THE DIRAFRAM WORKS ON ENGINE VACUUM 95% AND 5% ON AIR CHANGE
NOW YOU ALL HAVE THIS PROBLEM WHEN AT LOW SPEED HIGH GGSS IF IT WAS PRESSURE IT WOULD HAPPEN AT HIGH SPEED .
SO WHATS THE PROBLEM WELL SOME CARBS ARE CLOSER THAN SOME THE G FORCE ON SOME WILL AFFECT THE FLOW AND OTHERS ITS FINE AND THE ONLY THING IN A WALBRO CARB THAT IS AFFECTED BY GGGSS IS THE FULCROM AND SPRING THAT REGULATE FUEL FUEL FLOW IN THE CHAMBER THATS WHY WHEN YOU PUSH TO FULL THROTTLE IT FLOODS AND DIES .
HOW TO FIX IS A TRIAL AND ERROR YOU CAN GET DIFFERENT SPRINGS FOR A WALBRO CARB TO ADJUST POP OFF PRESSURE DO NOT CUT COMPRESS AS U CAN BUY 10 SPRINGS FOR ABOUT $5 .
WHY ARE SOME GOOD AND SOME BAD ITS BECAUSE IT WAS NOT DESIGHN FOR HIGH GGSS IT WAS DESIGHN FOR A CHAINSAW AND YOU NOT GOING TO GET 8GSS OUT OFF CUTTING WOOD .
IF YOU DO NOT BELEIVE ME SWING YOUR CHAINSAW AT 8 TIMES PER 3 SEC I DO NOT THINK SO .

AND WHY SOME WORK WITH THE TUBE AND BOX IS BECAUSE U ARE CHANGING THAT 5% OF PRESSURE AND DOING THIS WILL CREATE LARGER PROBLEMS LATER MAIN IS LEAN ON HIGH AND OTHER IS YOU WILL WEAR OUT YOUR DIRAFRAM PRETTY QUICK AND THEN U WILL HAVE MORE PORBLEMS .

Hasn't affected mine in this manner yet and I can't see the diaphragm wearing any faster either.

Srm99
The problem I am trying to avoid is a DA 50 (any gas engine) running poorly at less than ¾ throttle to idle. I have seen a DR 50 dead stick in an inverted harrier, low throttle and not many “G� at that point at my home field. I still don’t believe what I saw. I am also trying to achieve no RPM changes at any attitude. My other gas planes have a tube running into the fuselage to prevent this from happening but the fuselage is sealed. This trick goes back to when gas chain saw engines were used in RC. Nothing new here at all. The balsa box is a cool idea and I wish I came up with it first. I do not have problems with G’s on any on my planes. Gas engines should not stop in the air and are the most forgiving engine you could install in a RC plane. If you are hearing a slight change in RPM during upright to inverted you need to install this tube. If you are always messing with the HI and LOW needel setting like it's a glow engine then you need to try this. Set you engine up with out a cowl and then install the cowl and it runs different...you need this tube. Some pilots do not here or care about this. Maybe only 5% care? It is worse when most of the flight is a reduced throttle. The cost of a diaphragm is cheap compared to the cost of dead sticking a plane off the field. The diaphragm moves with every stroke and if I am running at less than ½ throttle I should have longer life.

srm99, what is with the ALL CAPS and I watched you video of your WH Extra on a DA 50 dead sticking in level flight what’s with that??? OH ya you might want to edit out kicking little kids on the flight line from your videos. We need pilots to keep this sport going.
http://media.putfile.com/Extras-Lucky-Escape

well i expected a personal attack and my problem with mine was a clunk line came off and with kid he knows not to come on the flight line and he could not hear me and if it hurt him have a look he had 3 jackets 2 x pants he had more protection than a swat officer . think if he ran straight into the prop a kick upthe bum is least of his worries .

now your problem 1/2 throtle to 3/4 throttle is a mixture problem not air flow maybe a needle dirty or wrong settings why do u think its the dirafram you are better off putting a bandaid on the hole if you think its airflow heres a test put your plane in position holding it in the move like knifeedge and try and recrate it on the ground .
you can ask any walbro mechanic they do have faulty carbis here mine has a forty gallon drum full off them
why do u think i posted this it is because i went down this track in the end i paid for a small engine mechanic with a walbro autherised mechanic as there were 2 planes exactly the same one mine one a freind we baught them togeather same mounting same cowel cut same most except servos his was doing what yours are doing mine is fine the mechanic said its the carbi straight away i was didnt believe him so we bolted his engine on mine . guess what it did the same thing so the problem followed he removed the dirafram from my mates engine and cheacked the pop off pressure and then looked at mine the pop off pressure was different so he made my mates pop off pressure the same as mine by changing springs altering the pop off pressure now no problems so thats where my theory is from fix the main problem not bandaid the surface .
well i know u dont beleieve me go to a small engin mechanic and see what he says .

Thats a better answer than "NOW TO AIR PRESSURE ON CARB PLATE IS A HOLE LOAD OF Sh%^ " and I never said I did not believe you. We are sharing what works for us. I have checked pop off pressure even on older carbs and never the same but the engine run fine for me using the tub run to the inside of the body. So what is the correct pop off pressure? If this is so critical why do the engine manufactures set this when they hand build the motor (like DA).

because most off them are ok and it will vary on plane to plane and how the engine is situated and the fuel system are only way is goto walbro and get some springs and try some will be worst some will be right on you need to find one that will suit your plane .
we are waiting from da the correct pop off pressure .

you have to remember da dont test your motor flying its on the bench .
to cure this problem da would have to spend big $ and get a carbi design for there motor but at the moment there supply of walbro is ok only 5% may play up and da will help u find problem .

I understand that the diaphragm must see atmospheric pressure. If you are saying that this is trial and error and every plane is going to be different how could an engine manufacture get it correct? I have not seen anything about changing springs in an engine manual. I have seen manufactures address this by having you install the tube. If putting a brass tub on the plate and running a tube to inside a sealed box or a sealed fuselage to give the diaphragm constant pressure may be a better answer. If the diaphragm sees more than atmospheric pressure the diaphragm will allow more fuel. If the diaphragm gets a negative pressure relative to atmospheric pressure it will cut off fuel flow. I am assuming that atmospheric pressure is equal to what you set the needles on the ground to (includes the prop blast) The small hole in the plate just has to see a constant pressure to give a consistent run. Some pilots just use a plate made from a soda can to divert prop blast. Some side mounted carbs stick out of the cowl and may not need anything. I can’t believe that the rear mounted carb will run not doing anything. This all assumes that you have good air flow into the cowl at all attitudes. Starving the rear induction card of air can cause similar symptoms.

But I am going to pick up some springs and I have a plane I can test this out on.

http://www.wind-drifter.com/technica...viceManual.pdf
read this about the spring page 6 7 tell u why in more tecnical mannner .

Thanks of the info
I will be running my new DA 50 on friday.

Food for thought My Evolution 58 comes with a fitting on the carb plate from the factory you run a line into the fuse.

All I know is my own experience and running the diaphragm cover atmospheric pressure hole to inside the fuse made my engine run the same in the air as on the ground, perfect idle, smooth transition with no burble all the way to WOT. Mine DA50r used to go lean inverted and I was always concerned it was going to quit. Now no matter what attitude, what maneuver the engine now runs perfectly. A simple thing to try IMO. Good luck.

srm99, I realize you are sincere in your belief that turbulence around the carb doesn't matter, however, I don't agree. I have on two different planes had to run a static line from the carb to the fuse. You mentioned trying without a cowl to see what happens....I did that and my plane ran as well in the air as on the ground but put the cowl back on and it just sputtered in the air. I ran the static line and solved the problem...easy.

Larry

What was your out vent hole size how many times to inlet
plus i notice you dont have a da50r the rear type carbi was intraduced to stop direct airflow on the carbi and maybe the direct flow on your dirafram but the same priniciable exits

what u are doing is slowing down the dirafram by adding resistance that meens your springs needs to be firmer not a tube .
its easy to dismiss but have you tried doing it?????????????????????????????????

sorry for editing but your carbi dirafram is at back of motor so no direct airflow could cause your problem more like not enough venting

If the Carb is in the cowl, it doesn't matter if it is upside down, backwards, on the side of the motor, rear carb, in the cylinder, in the prop[:-], it is still affected my turbulance in the cowl,,

Well guys I just got back from the flying field and the DA ran great out of the box. I used the needle settings the way DA set them for the first flight. It ran a little rich as I would expect. It ran exactly the same in the air as on the ground. I did only one tail slide at idle and no problem going back up on the throttle. Knife edge left or right and in down lines no change in RPM. I had instant response to the throttle stick with even the rich settings. Did an upright somewhat flat spin at idle with no problem. Far as I am concerned the balsa box works great. Only 10 minute flight and how I am going to set the needles and that is the end of that.
Thanks jongurley great tip
Later,I have some flying to do.

Cool ! I have the carb plate on my Yak right now and so far I havent had any issues..I may try the box idea just to see if it gets any better..

What is your idle set at ? I believe mine is about 1300 for landing and when flying I keep it a little higher around 1600

I was so happy it ran good I forgot to tach it but it was not moving on the ground and it was set lower than my G 62 with electronic ignition runs at (sounds slower) Once I get the card set I will tach it. Hay if the plate works just go fly. I did not advance the trim on the TX to up the RPM in flight. I had good breaking when I went to idle in the air. Sounded very very slow. I would guess the box is helping that low RPM. ROCK solid. I removed the tube to the box (on the ground) and the engine ran the same when the cowl was off. I was at a higher idle at the time so I did not test it for how low I could go. I just put the cowl on and started again. Very smooth motor at idle.

I have been reading the Walbro Service manual from "srm99", this is a must read guys.

So far the only thing I get out of it is that the carb is very sensitive to the inernal adjustments and if I read it correctly also the diaphragm. There may be a spring tension that will work in your cowl set up but I see no way to get a good running engine with out alot of different springs and flying to check it out. Everyones plane would be different depending on cowl cutouts. I do have a older plane I can test this on.

Side note: I used contest grade balsa 1/16 inch. I did not seal the balsa. I am at 550 feet above sea level I would think the balsa will act like a filter and will slowley adjust to changes.

SORRY JOURNEY
EVERY POSITION OF motor inside a cowel will affect the running 95% u will not even notice the change .\
have you read the manual i posted dose it make sence to you yet .

3dsky i notice you read the manual
am i vindcated on what i was trying to express as u and all know chasing a problem is the bigest wast off time in our industry of flying u just want to go and fly i was the same beliefe as you guys until i paid for the pros they showed me a lot i even worked with them a few saturdays to get better understanding .

I should have mentioned I don't have a DA50 but the issue of turbulence around the carb is common to all makes in my opinion.

Larry