I am almost finished putting together my ARF and I have a question. I don't know which position to hook up the throttle in. When the engine is idling, where should the stick be on the radio? Middle? Towards the bottom? My first thought was to open up the carb all the way manually and hook up the throttle servo with the radio stick all the way in the "up" position. I looked through all the instruction for the radio, engine, and plane but neither mentioned the correct procedure. Help!!!

Throttle stick at top, carb wide open. Gives you full throttle.
Throttle stick at bottom, carb almost closed. Gives you the slowest idle speed the motor will do dependably.

(The above is a simplification that really doesn't cover some very important details that're actually simple and easy to do.)

You want to rig your connecting rod from the servo so it's length results in the servo arm being at 90degrees when the throttle stick is centered and so that the carb is halfway open.

And have the connecting rod positioned in the servo arm's holes and the carb's arm holes so that when the throttle stick is at the top, and the carb is wide open, the servo arm is roughly at a 45degree angle. And when the throttle stick is at the bottom, the servo arm is at a 45degree angle the other way.

There is more.........

Easiest way to do all that is to turn on your radio and turn on the airplane so the servos will center. Have the throttle stick and it's trim centered when you do this. Then turn off the RX and then the TX (in that sequence).

Now roughly set the length of the connecting rod so that when it's connected to the servo arm and the carb arm, the servo arm will be at 90degrees and the carb arm will be halfway from full open to full closed. Now plug the connecting rod into the carb arm at the farthest out hole. And plug the connecting rod into the servo arm at the hole that's next to the hole that's closest to the inside.

Turn on the TX and then the RX and look at what happens to the throttle arm when the servo arm is centered. Remember to have the throttle stick at center and it's trim lever at center. The servo's centering won't change, but the throttle arm might not still be in the center of it's full-to-closed throws. Keep your TX's throttle stick at dead center and it's trim at dead center. Adjust your connecting rod length so that the carb arm is centered. You want the servo to be centered with it's arm and the connecting rod making a 90degree angle, and you want the carb arm holding the carb halfway open..... or halfway closed if you think that way.

Now move your throttle stick full up and full down. You want the carb to open fully and also close to the perfect idle position. (But since the engine isn't running (it isn't is it? grin) you're not going to know if the setting is the perfect idle position.)
If the carb isn't opening and closing enough, then change the connection on the servo to use a hole that's further out.
If the carb is opening and closing too much, you might hear the servo buzz or see the connector rod bow. Move the connection on the servo to use a hole further in.

If you think the carb is opening and closing "close enough", you can use your radio to fine tune it's End Points so that the carb opens and closes perfectly.

there is more..........

You really want to do all the settings physically to set the hardware on the airplane as nearly correct as possible. You don't want to use the radio's capability to modify end points or change servo centering or increase/decrease throws until you have the hardware set up as good as you can get it.

If you don't setup the airplane worth spit, the radio may be able to cover the mess, but........ I've had to help a number of people who're members of the "I bought that expensive radio so I don't have to know how to actually setup a model worth spit" club fix "problems with their crummy engines". Learn to rig your connections "manually" and you'll bypass a bunch of lousy flying models that aren't lousy flying models at all.

I helped one of those guys just the other day whose elevator "was designed wrong". When I suggested that the connector rod was too short (and it's servo wasn't square either) he wanted to fix it with his radio. Since he'd already "fixed it" with the radio when he "built" the model, and the radio was all out of "fixing" adjustment, he was in a fix. After squaring the servo/connecting rod, adjusting the rod to length, and moving the rod connection out the elevator horn from the inside hole to the outside hole (he knew the model was designed poorly because the thing was way too sensitive to elevator input), he decided that the problem was that his expensive radio wasn't good enough..... chuckle..... anyway.......

Once you have the throttle setup "the old way", your computer radio will tune the sucker excellently well, and you won't be stalling the throttle servo or flying without full throttle or with a motor that "won't idle down all the way". I've seen two models in the last month that "wouldn't idle down enough" that just needed the hardware rigged correctly.

there is more.......

Idle speed............ And how your radio works to shut down the engine..........

Some radio's have an engine kill button. They're kewl. Heck, they're excellent. But sometimes, if you don't setup the model decently before asking the radio to tune the throws, that button won't kill the engine. And you want to be able to kill the engine, trust me.

Setup the throttle servo arm, the connecting rod length, and the carb arm halfway decent and the radio will have a chance to help you do the rest. That said..........

You want the throttle stick and it's trim to work for you to set the engine's idle speed. And you want the radio to be able to kill the engine. Some radios have a kill button and some don't. The ones that don't will work for you if you have enough movement on the throttle trim. The kill button has already been covered. Manually setup the model and the kill button will probably kill. If you don't have a kill button, then the idea is to use the trim lever to kill. You'll simply run the trim down and the engine will die. But there's more to that deal....... (there's always more, right?

If you setup the model manually, when you pull the throttle stick down to idle, the engine is going to go to some kind of idle. If it dies, just click the trim lever up some and try again. The idea is to adjust the engine idle speed with the throttle trim lever until you've got a steady low speed idle. You want the lowest the engine will dependably idle on the ground. It will idle a bit faster in the air, but that's what you want also.

Once you've established where that good idle position is on the trim lever, look hard at that trim position and remember it. When you're flying, leave that trim alone. You might want a click faster, but for the most part, leave it alone in flight. When you land and want to kill the engine, just pull it down and the engine will die. As soon as it dies, push the trim back to the good idle position. Do it then, not later.

OK, you're good to go.

Hope this helps you.

You know, it took awhile typing it, and it looks complicated, right?

It isn't exactly simple until you walk through it. But it really is logical and easy to do. And it's the basics of radio control so you'll need to know it sooner or later if you want to do this stuff for yourself.

Have fun. I just looked out the window and darned if it isn't somewhat calm out there..... I'm goin' flying, see ya'. BIG GRIN.....