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Nov 10, 2017, 07:31 PM
Registered User

DA-50R Engine Gurgling Sound

I have a used DA-50R with low hours before running I sent it back to DA for a check up, new bearings, rebuilt carb, new plug wire etc. Once I received it back it was installed in my new Goldwing Yak 55SP, 88". It runs great on the ground and transitions from low throttle to med with no hesitation. Once in the air it gurgles from low to med throttle but from med to high runs great. Is this the normal sound of a Slimline Pitts Muffler or the DA 50 itself? I have soldered the carb metering plate hole and added tygon tubing inside the fuse for static air psi. I have noticed by leaning in small increments the high needle has helped.
The needle settings somewhere on low needle less than 1 1/2 turns and about the same on the high needle. The motor runs great and cranks with ease only the gurgling sound when operating from med throttle to low. (Fuel, 89 octane ethanol free with 40:1 Redline Syn. 22 X 8 Menz Prop. Does this sound like tuning problem or air intrusion to the carb??
Last edited by mgnowell; Nov 10, 2017 at 09:31 PM.
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Nov 10, 2017, 09:38 PM
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I have a feeling that your low needle is too rich. You may also want to open the plug gap to .024. You don't need any more octane then 87, your 40:1 ratio is just fine. Your prop load is a bit light. I always ran a 23x8 on mine.
Nov 12, 2017, 09:19 AM
Registered User

DA-50R Gurling Sound

Thanks for the reply I did lean the low needle 1/8 turn and flew it each time until it quit running on take off, I have a new Menz 23 x 8 prop on the way and will lower the octane to 87 non-ethanol with the redline 40:1 ratio. I read reviews where other DA-50's run high grade up to low lead 100 octane without this problem. DA recommend's the spark plug gap at 0.18 to 0.20 mine is 0.19. I'm also running Pulse 7.4 Lipo Battery's with a Areo-Tech Ignition around 5.3 vdc output.
Nov 13, 2017, 03:24 PM
Registered User

DR 50 gurgling

How much fuel is through the engine? A DA 50R will "burble" at low to mid range when less than 4-5 gals of fuel have been run through it. The ring needs to seat, and if all else is good the burble will become less or go away. The burble can also be caused by carb needles to rich or to much air (pressurizing) the cowl from air flow. The Yak has a very open front on the cowl.
I know you said you did the carb mod to put a fuel line on the carb hole into the fuse, that's good.
You didn't say what your max rpm was. The 22x8 prop is fine depending on the max rpm your getting on the ground. Should be about 6800 to 6900 depending on your altitude and needle settings. I still run a 22X8 Xoar wood prop and get 6900 at near sea level with 93 oct non-ethanol fuel. I have a Slimline pitts muffler on an Extra 260 and still get some burble. I have learned to live with it.
Sounds like you leaned it to far on one of your flights. My low needle is about 1 1/8 and I think that is right on the border of being to lean. My high needle is 1 3/4 out. Your spark plug at .018-.020 is ok for now, check the color of the plug without idling much (like after you land and shut it off right away), should be a desert tan. Whitish is to lean and brown is to rich, milk chocolate is close. Also, search on some of the other rc web sites for tuning gas engines.
Hope that helps, happy landings!
Nov 13, 2017, 08:18 PM
Registered User

DA-50R Gurgling Sound

Thanks rica1 for you help, I really don't know the amount of fuel through my engine because I bought it used with low hours, it looks new with no oil stains anywhere. I sent it back to DA this summer and they replace bearings, rebuilt the carb and changed out the pick up cable. This past weekend I changed the plug gap from 0.19 to 0.20 I replaced the prop with a Xoar 22 x 8 made small (H) & (L) needle adjustments which seemed to help a lot. The gurgling sound is not as bad between low & med throttle now. Do you think I should run a petroleum base oil for several gallons to be sure the ring seats. I talked with Casey at DA once I received the engine back in June concerning the type oil and he suggested Redline 40:1. I know DA run the engine after repair, sea level at our flying field is around 320 ft.
Nov 14, 2017, 02:25 AM
Registered User
If the eng idles good without loading up for 20-30 seconds, and then transitions from idle to high very quickly without stumbling or lagging, your good. If your getting 6700 to 6900 rpm on the ground with the 20x8 prop, your high needle is set good. It will run a little leaner in the air when the prop unloads.
You can run Redline from the start, it will just take longer for the ring to seat. Not a big deal, don't worry, as long as the eng runs reliably.
Without knowing how much fuel is through the eng and you get more time on it you may need to lean the low needle slightly if it's a low time eng while the ring seats.
Be careful though, to lean can be dangerous! A little rich the eng will tolerate but not lean. Once the ring seats and your needles set at a good tune, you should not have to adjust the needles.
I like to know where the needles are set (and write it down) as I have had some engine needles change over time (probably vibration) and wonder why the eng is not running as well as before, so I can quickly set them back to where it ran good. Check the color of the plug once in a while, if it's tan your tune is good.
Happy landings.
Nov 21, 2017, 06:57 PM
Registered User
Go here to post #2. Tried and true method for tuning gas engines.
Nov 25, 2017, 07:13 PM
Registered User

DA-50R Gurgling Sound

Thanks Raven1978 for the info, I will use this from now on.
Nov 30, 2017, 03:28 PM
Xpress..'s Avatar
Yes that is an excellent tuning guide and Terry Wiles is a close friend of mine, I have used his method many times to tune my engines.

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