DA 50 problem
 

I am still in the break in period with my new DA50 aboard a QQ Yak 54 80", so far about 1 gallon through it. Oil is mineral (Castro Super TT) with 1:32 mix, as recommended. Engine is mounted inverted in the plane, and muffler is pitts style. I fly at 700m (2100 feet) above sea level.

Engine starts fine, and transitions are ok too. High and low needles were untouched and remained at factory settings. The problem I experienced is that when flying it sputters continually. I thought that it was caused by the high needle being set too rich. Curiously, when flying inverted the engine sounded much better and very smoothly, with almost no sputter at all. I adjusted the high and low needles but no matter what I do the problem persists. I don't know what else to do, as the only variables that I can play with are these two needles.

Any helping hand on this? It will be greatly appreciated.

Thank you all in advance,

Fernando

RE: DA 50 problem
 

Adjust low needle (the one closest to the engen) in or lean it till the engen will not transition to high speed, then richen it till the engin will trensition good.
Then adjust the hight speed needle for max rpm, then back it off lor richen it till you loose about 200 rpm.
After that you can check the low end again.
Good luck.
I am watching you
Larry S

RE: DA 50 problem
 

Set High needle to max rpm then back off 200-300 rpm, Then start adjusting the low needle for good transition. Usually the burbling is caused by a to rich setting on the low end, so adjust the low needle 1/8 turn at a time.

RE: DA 50 problem
 

Both these guys are right... tailstrike perhaps has the "faster" tune. The needles are interelated to some degree... meaning when you change one, the other is effected some.

Go for the transition first with the low end. As you lean you will also notice the engine idling higher... you'll need to set your throttle endpoint lower to lower your idle. So many people miss this and they use the low end to get a reasonable idle. but first get the transition til it hesitiates (a quick, almost quit effect) then back off 1/16 turn.

Then set the high end with a tach to peak RPM minus 200 rpm... then set the throttle endpoint at idle until the idle is around 1900-2000. You'll hear how guys like to get 1500-1600 and maybe that's necessary for asphalt... but at even at 2100 your plane shouldn't move on grass, and the transition is faster.

THEN... repeat this process again as chages to the high end may have changed the low end significantly enough to be too lean or rich. This will get the needles right where they should be for your setup, altitude, etc.

RE: DA 50 problem
 

Leans out inverted? Wonder why?

RE: DA 50 problem
 

I had the exact same thing...

I did two modifications at the same time so I'm not sure which was the fix.

#1 mod: I covered the 1 inch hole on the firewall directly opposite to the carb intake with thin balsa. (solution to airflow problem as it enters carb normal versus inverted flight)

#2 mod: I soldered a 1/2 inch long copper pipe (I believe it was 1/8 inch size?) onto the carb plate where that little breather hole is, put a piece of glow fuel line on it and put it through a little hole in the thin balsa to the fuselage. (solution to airflow problem which leads to changes of air pressure inside the cowl for normal versus inverted flight. Instead you get a more steady air pressure senced) This is similar to the "balsa box" mod that many have tried successfully. For me, that mod did not work.

Also, you will find that after break-in the engine will be little more smooth and generate more power. My engine peaked at 7000 rpm using a bambula 22-8 at around 5 gallons using 100:1 synthetic. (all this in Calgary at around 4000 feet above sea level) Inexplicably my rpm has dropped to 6800 rpm after richening it to about 80:1 and it hasn't improved since going back to 100:1.

Any thoughts folks? Spark plug perhaps?

RE: DA 50 problem
 

Thank you guys. I will take the cowl out and do the needle fine tunning first to see if I can fix the problem. This wednesday is holiday and should be perfect to do it. Will let you know how it goes. I really need to feel confident with the engine before I start doing 3d on this new aircraft. Looking forward to that.

Fernando