I'm trying to start a new unknown engine that's on a 1/3 scale citabria. It's never been started and I don't know how to set the screws for starting. The engine looks like a zenoah but the label says "U.S.E. Engines-Syracuse N.Y." I tried to Google them and yellow pages but no luck. The carb looks exactly like a zenoah. There's a high speed and a low speed screw. How should the throttle be set? !/8? 1/2? Full? The carb doesn't seem to want to take gas. I removed the fuel line from the carb and applied air pressure to the overflow line and the gas flowed freely. But when hooked up to the carb the fuel doesn't move through the line when air pressure is applied to the overflow. Any info is greatly appreciated.- Arnold

Both needles at 1-1/2 open from fully closed for initial starting, then adjusted from there for performance. It's a U.S. Engines product. Pretty much along the lines of most Sachs based engines.

Remove the cover plates from the carb and replace the diaphragm and pump membrane with new from a rebuild kit available at most any saw and mower shop. Or browse online for a rebuild kit that relates to the carb model number.

I would start by taking the plug out, and turn the engine over with a starter to see if you can get any fuel through the carb. You should see it at the carb throat. If not, then disassemble the carb and check the diaphram (too stiff or hard, replace), the float valve (I know its not called that) see if it moves up and down. It might be stuck. WD-40 through fuel passages to make sure they are clear. Its where I would start.
If fuel IS getting through, ground the plug and turn the engine over with a starter and see if you're getting spark.

Edwin

If the pump membrane inside the carb has dried out or warped it won't matter how well gas flows though the line. The pump can also stick due to dried or gelled oil residue inside the carb. The carb pump just won't move fuel. If a used carb sits for a long time it's very common for the pump to quit working.

Thanks for your info, Edwin and Tired Old Man, that gives me someplace to start. I'll do those things (and get back to you). Thanks-Arnold

If it's a brand new engine, the carb needs to be primed. Take both needles out and squirt fuel in the holes. Let it sit for a minute or two. Squirt fuel in the holes again. Run both needles all the way back in until they stop. Now back them both out 1.5 turns and start it. Tune accordingly.

I can't see a brand new engine having gummed up diaphragms or dried out diaphragms. It's never had any fuel through it. Shouldn't need to replace brand new pump diaphragms. [:-]

Try priming it first.

Good idea, Rcpilot, I'll try that first. What do you suggest for throttle setting for starting, 1/8? 1/4?

I like to set my TX to fast idle with the trim button. I usually start there. It's hard to tell you exactly how much the carb should be open for that very first start. I wouldn't open it up to 1/4. Thats a lot and is dangerous. Anything just above idle will allow it to pull in enough air to fire. If it won't fire try and crack it open a bit more.

Of course you want to choke it first and get it wet................. had to say it. Ya gotta be a lawyer around here or somebody will call you an idiot for not mentioning it.

Will you be using an electric starter? Or hand flipping the prop?

Failed to note that it was new... At least you managed to note the choke

OK, I've primed it, cussed it, flipped it, and even tried to use a kluged up rope start (which actually worked) but she has yet to fire. My old Tork starter won't turn it over. (So back to the drawing board) I guess my next step is to find a stronger starter. I don't know the displacement of this engine but it came with a 18/8 prop so it must be around 35 cc, would you say?

Well, I took the plane to the model shop where the owner, a knowledgable old gentleman, took one glance and said it was a Quadra 35. He adjusted the needle valves, stuck his thumb in the carb opening and jockeyed the prop back and forth, (all the while I'm watching somewhat amazed) then he wound the prop backwards and let er go. It cranked. He looked up with a half grin and said "bet ya didn't know it was spring loaded." After he adjusted it I took it home and tried to replicate what he had done but couldn't. Couldn't even get it to fire once. So I'm a little discouraged. What good is a plane I can't start? BTW, if you have a spring loaded engine don't wind it up more than 3/4 turn or it might smack your hand, as I found out the hard way.[&o] I've got stitches to prove it. I appreciate all of your posts.-Arnold