the way up to the carb. Choke the engine just enough to fill the feed line with fuel and draw a little into the carburetor. Don't overdo it or you may flood the engine, making it difficult to start.

Connect the 1-1/2 volt glow plug battery, grasp the prop blade firmly in the palm of your hand with your fingers clasped completely around it, then slowly turn the prop through the compression cycle. You wilt probably feel a slight "bump", which is the ignition of the fuel as the engine tries to fire. A bump indicates correct fuel mixture. If you don't get a bump the first time through, keep turning the prop through until you do, always holding firmly onto the prop blade. Don't worry about the engine starting, a single firing will not break your grip on the prop.

After the bump is felt, start flipping the propeller smartly counter-clockwise (as viewed from the front). Remember that any time the battery is hooked up, the engine has the potential to roar to life even with the most casual flip of the prop. As you flip the prop through compression be sure to "follow through" with your stroke to get your fingers and/or chicken stick completely outside the prop arc. If the needle valve is set close to right, the engine should start running and stay running at a rich setting. You may have to try several different needle settings before the right one is found. Open or close the needle a half turn at a time until the engine will start and stay running.

Once the engine starts, move around to the back of the engine to remove the battery and make further adjustments to the needle valve. Never stand in the prop arc - a thrown propeller blade is very rare, but it can happen and could result in a major eye or other injury.

TROUBLESHOOTING

ENGINE WON'T START OR EVEN "BUMP": Could be a bad glow plug or not enough prime. Check the plug first by taking it out of the engine and hooking it up to the battery. You should be able to see the glow plug element glowing brightly. If it's okay, put it back in the engine and rechoke the engine to be sure it's primed adequately.

ENGINE "POPS" BUT WON'T START: Too much prime or needle valve set too rich. Close the needle valve and continue to flip until it stops popping. Reset the needle valve a little leaner and try again. It may need a small prime to get it going.

ENGINE STARTS, BUT DIES QUICKLY: Needle valve set too lean. The engine is simply burning off the prime. Open the needle valve one turn and try again. If the problem persists, the fuel line may be kinked or clogged, or the carburetor may have dirt in it. Correct those problems before trying again.

ENGINE STARTS, BUT DIES WHEN YOU DISCONNECT THE BATTERY: Needle valve set too rich or bad glow plug. Start the engine again and start closing the needle valve before disconnecting the battery. If it still dies when the battery is unhooked, try a new glow plug.

ENGINE STARTS, BUT RUNS ERRATICALLY/ WON'T HOLD A SETTING: Fuel system problem. While engine is running, check the feed line for bubbles that could indicate fuel foaming in the tank or a hole in one of the fuel lines (possibly even the clunk line).

Starting with an electric starter. Keep transmitter within reach and always have someone hold the airplane.

ADJUSTING THE ENGINE

The key to successfully running a model engine is learning to adjust the needle valve. The needle valve controls how much fuel the engine is getting. Opening the needle valve (screwing it out) allows more fuel to flow into the carburetor, richening the mixture. Closing the needle valve (screwing it in) restricts the flow of fuel, leaning the mixture. You must learn to identify when the engine is getting too much fuel (running too rich) or too little fuel (running too lean).

SETTING THE NEEDLE VALVE: It's fairly easy to set the needle valve by "ear" — using your ears to listen closely to the effect your needle valve adjustments have on the engine. An engine that is running too rich sounds unsteady, like it is misfiring part of the time. The sound is often described as "blubbering", "burbly", or "4 cycling". In this condition, the engine is actually getting so much fuel that it is indeed misfiring every other time, causing it to run slow. As you lean out the mixture by closing the needle valve, the sound becomes steadier and the tone will rise as the rpm's increase. At its peak setting the engine will sound smooth and powerful. Eventually you will pass the ideal setting and go over-lean, causing the engine's tone to slow down or "sag" from overheating. Running an engine too lean is the quickest way to ruin it! If you ever hear the engine start to sag while you are screwing in the needle valve, quickly turn it back out before the engine completely seizes up. For best results, you must learn to adjust the needle valve on the border between rich and lean to achieve satisfactory performance and long engine life. Never set the needle valve for exact peak rpm, always stay on the slightly rich side, because the engine will gradually lean out in the air as the tank empties.

Four-stroke engines are more difficult to set by ear because their tone changes very little as the mixture is adjusted. To set a 4-stroke engine reliably, a handheld tachometer (reads the exact rpm of the engine) is a virtual must. Starting on the rich side, slowly lean the engine while reading the tacho at the same time. The rpm should rise, hit a peak, and drop slightly. As soon as you see a drop, you know the engine is over-lean and must be richened. Open the needle valve until you hit peak again and continue opening it until the rpm drops about 100 to 200 below peak, on the rich side.

THE FINAL TEST: Before every day of flying you should perform a simple test to check the needle valve setting. With the throttle wide open, point the nose of the airplane straight up and hold it there for 5 - 10 seconds. If the engine runs steady or picks up a few rpm, you're ready to fly! But if the engine picks up rpm and then starts to sag, the setting is too lean and the needle valve needs to be opened slightly.

Once you have the main needle valve adjusted properly, you can move on to adjusting the idle.

SETTING THE IDLE: Getting a slow, reliable idle is probably the trickiest part of adjusting a model engine for flight. Rather than shooting for a super low idle, it's smarter to settle for a more dependable idle at a slightly higher rpm. Your throttle linkage should be adjusted so you can pull the throttle stick all the way back to a fast idle with no danger of the engine quitting. Then you can bring the throttle trim lever back a little at a time to set the precise idle speed you want.

If your engine quits as soon as you bring it back to idle, you will have to adjust the idle mixture. Different engines have different means for adjusting the idle mixture. Some have another smaller needle valve on the opposite side of the carb as the main needle valve, while others have a small air bleed screw to control the idle mixture. It's very important that you read the engine manufacturer's instructions to understand how your engine's carburetor is designed to work. Adjusting the idle mixture control is a lot like setting the main needle valve; you have to listen carefully to the effect your adjustments have on the running engine.

Start your engine and run it at high speed for a minute to warm it up. Then pull the throttle back to proper idle speed and listen carefully. If the engine speeds up a little and then dies, the idle mixture is probably too lean. Open up the idle needle valve or close the air bleed screw a little bit and try it again, make only small turns in your adjustment. Many times people go right past the best setting by making too big an adjustment. If the engine slows down gradually and eventually stops, it is "loading up" with excess fuel and is too rich. Close the idle needle valve or open up the air bleed screw. Once you get close to the correct setting, let the engine idle for 15 - 30 seconds and then quickly open the throttle. The engine should transition easily to high throttle, without hesitating or quitting. The test simulates a long landing approach aborted at the last moment, where a conked-out engine can leave you short of the field and in trouble.

Don't get discouraged if it takes a while to get your carburetor adjusted properly. It isn't easy, only practice and learning what to listen for can get the job done.

The nose-high test for checking the needle valve setting. ENGINE BREAK-IN: Just like a new car, motorcycle, or any other internal combustion engine, a model engine must be broken in before it will develop peak power and reliability. Always follow the engine manufacturer's recommendations concerning break-in procedures. Most modern R/C sport engines won't need an extensive break-in on the ground. Fifteen to twenty minutes of running on the ground with a rich needle valve setting should break the engine in enough to allow it to run out a full tank of fuel without stopping. During the initial ground running, keep the throttle wide open. Vary the needle valve setting from a very rich, slow, burbly setting to a slightly faster, but still rich, setting. Go in and out with the needle valve every minute or so, until the engine can be run at near peak power without getting overheated and slowing down. The final break-in of the engine can take place in the air. Keep the needle valve setting slightly rich for the first 3-4 flights, gradually leaning it out a little more each flight until the ideal setting is achieved.