Hello all-

Please pardon the very newbie question. I am coming over from Nitro engines into my first gas engine, a DA-50-R.

It's used, but I've flown the plane with this engine and it pops in about 8 spins choked and then turns over in 3-4 after that and always turns over on the first good flip after that for the day. I believe the engine is in good shape overall.

Now that I have the plane home (Airwild Extra 260) I am setting it up with my radio and I just don't understand how to know when the carb is open and when it is closed. The DA-50 manual I downloaded doesn't have any information about the carb.

Before I try and set this up on my radio properly, I really wanted to get the throttle basically working so closed was closed or mostly closed and open was open so I don't flood the engine trying to start it for the first time (etc., all).

The engine is mounted inverted.

On a nitro, I obviously can see the air intake opening and of course get a really good starting point for open vs closed by looking at that. But, on this DA-50, how do I tell? Which way should the throttle move? Towards the front of the engine for open?

Thanks for your patience and support of new modelers coming into gas engines.

You really answered your own question. Just look in the carb and like your glo engines, you will see the throttle butterfly operate when you move the arm. Easy enough to tell which way is open. On some gassers including the DA, sometimes there is an idle stop screw ... if that is present, when the throttle arm is against that stop, you know it is at idle. But, most gassers have these screws removed so you can't count on these. My DA pulls the throttle arm to the rear of the airplane for full throttle but I would not guarantee that all DAs are the same.

Truckracer,

Thank you for your reply. I know it must sound like I am insane, but the unit seems completely sealed to me. I don't see an air-intake. Here are some pictures. It must be right in front of me. I took the 4 screws off the plate in the fourth picture, but it had a rubberish membrane underneath it so I didn't want to mess with it since I (clearly!) don't know what I am doing.

I can't see inside the carb because of the firewall. These pics are opposite the arm. Do you think I am fully open or fully closed in the second picture?

Hey bud,

I think DA would recommend a hole drilled in the middle to let the carb breathe a bit more, but don't quote me on it. Give them a call or shoot them an email to see what to think. To answer your question, the throttle arm is springloaded to move to idle. Pulling the arm back will open the throttle, and moving it forward will close the throttle. Does that help?

BTW, the arm I am referring to is the pretty red one.

In the second picture you are fully closed. The whole that is threaded and empty would be where the idle stop screw would go. DA doesn't include these with their carbs.

I agree with zope pope, you need a hole in your firewall for air passage. The carb air intake is flush with the firewall and that just won't work. You're going to have to remove the engine to cut the hole so you can look into the carb intake at that time to see the throttle butterfly. You can get familiar with your carb at that time and make some notes which way your throttle arm should move. How big should the hole be? I'd make it at least 1 1/2" and larger will not hurt anything. You can cut it with a small hole saw. I don't know what airplane you have and whether there is free air available in the box behind the firewall. A large hole will allow free airflow around the carb. If in doubt, make the hole as large as possible without sacrificing firewall strength for the standoff engine mounts.

It looks to me you have plenty clearance between carb intake and firewall at least 7 mm going by the photos which would be plenty,i wouldn't go cutting into the firewall,run it first.You will probably find it will perform fine .Did it run ok previously?.Carb is at idle/closed with throttle arm at angled threaded section as previously mentioned.

I'm in agreement with zope_pope and Truckracer.

While the engine will probably run with it that close to the firewall and no hole, it certainly won't run well. There is actually a formula for figuring the necessary minimum clearance from the carb inlet to the firewall, but it basically boils down to you need at least the diameter of the carb intake i.e. a carb with a 5/8" intake would need at least a 5/8" clearance to the firewall and that's the minimum.

JMHO...

I guess I just prefer a nice large clearance hole so I don't have to worry about whether it is large enough or whether it interferes with airflow. I'm sure there are many ways of doing this sort of thing right. I have experienced carbs that are next to cowls where a hole was cut and it was not big enough. A larger hole solved the performance problem in these cases.

If you cut a hole, at least you can see in the carb intake. Also, a mirror on an extendable wand is a lot of help when you are trying to get a look in there.

AS Desert Aircraft says in the instructions, don't listen to someone on the internet. Call Desert Aircraft!! There number is 520-722-0607.

Yeah, it ran great actually. I flew with it three times with no problems. No hesitation or anything that I could tell. Starts great. Runs great. But, I do appreciate the inputs here.

I'll do some searches on what sort of things to look for if it's not getting enough air. If you know of any symptoms to be on the look out for, please let me know.

Vahn

Yes. very much so. Cheers!

http://www.desertaircraft.com/manuals/50Manual.pdf

Glad to be able to help. Check out the DA manual. it mentions atleast 1" of clearance from the firewall. If that isn't possible, drill a hole larger than the carb inlet. Its on page 3. Cheers!

Reduced top rpm would be noticed if airflow was restricted.Although i dont believe you'll have a problem as it is.

And you can't always listen to DA either. I learned that first hand.

I've had that same experience with DA. Usually after I have had some service work done on an engine there, when I call to see exactly what was done (usually an improvement at no cost to me) they usually deny knowledge of things that are clearly visible on the engine when it came back. For example, recent carb changes that greatly improved my DA-50 midrange ... yet they said they did nothing to the carb and physical things on the carb were different. Its like the guy who answers the phone doesn't really know what the guys in the back shop are doing. Now this is not meant to blast DA in any way, my (2) DA engines perform very well and so far, I have never had to pay a dime for normal (not crash damage) service. But phone conversations with DA have usually left me wondering why I bothered to call in the first place.

I have to stay away from this one. I just have to... Aww, heck with it. Check out a few of the neighborhood gas lawn mowers. The throttles all work the same way

We don't have gas lawn mowers where I live (So cal, no grass!)

But, all kidding aside, a rear-facing carb that's not that easy to see even with a mirror and pinlight, combined with zero gas engine experience, a used engine already mounted and no desire to take it off right now, I don't see any harm in double checking your assumptions and getting some opinions on how to best proceed.

So, for those you not laughing at me out loud, thank you so much for your time and points of view about where I should go with this.

I'll pay extra attention to the top end and keep an eye on if I should put a hole in the firewall. I prefer not to do that, of course, but it's now on the list.

I'm taking this project really slow, one step at a time, since it's the largest plane and engine I've owned and I'd be lying if I told you it didn't scare me a little bit right now.

I believe I have this set up correctly now in the basic sense. I confirmed what everyone has been saying about the direction the arm should be swinging. I still can't see inside very well (not as much as I can see on any given glow engine) even with a small mirror, but I believe I am fully open and closed (throttle arm as far as it can go before it starts bunching up, the middle being the estimated middle, etc all).

I'm now just waiting for my Optical Kill, and then I'll try and start it on my own and fine tune the throttle travel adjust/end points appropriatly. If needed, I'll then move on to the low and high end needle adjustment. Then (if neccessary) I will drill the hole in the firewall. The pilot who had this setup before didn't use an Optical Kill, but I want one and they seem common for every gas engine plane at my field from 50 to 150.

If your not sure which way round the throttle is going to go please make sure you have someone hold on tightly to your plane when you start it, as you may get a suprise!!

Heh. I'm sure now thanks to the helpful people on this forum. But, of course, I have tie-downs I'd use anyhow if doing it alone.

Again, the whole point of the thread was to make sure I didn't get a surprise by setting it up correctly in the first place and making sure I didn't flood the engine trying to start her up the first time. I'm still waiting for my optical kill before I try, which should provide yet another safety net.

Vahn

Good decision on the optical kill swtich. It is what i use as well and it will ALWAYS shut the engine down.