Here's my engine tuning procedure:

1. Start the engine, leave the glow starter connected, and run the engine to max throttle for a few seconds. This clears out the exhaust, heats the engine up, and ensures your glow plug is up to temperature.

2. Return to reliable idle speed with the throttle and remove the glow igniter.

3. Using a tachometer, go to full throttle. Now start leaning out the High speed needle (thats the big one). RPMs should rise to a peak then begin to fall off. Find the peak, and then back the needle out again a few clicks such that you are running at 200-300 rpm below your peak speed TO THE RICH SIDE.

4. Return to reliable idle speed. If you were very rich before, you'll find your reliable idle speed may have dropped slightly. This is good.

5. Wait 20-30 second, then punch the throttle to full. If the engine goes to full speed without hesitation, you're done. Go fly.

6. If the engine hesitates, and then goes to full throttle, you're probably a little too RICH on the low end. Stop the engine, LEAN out the low end by 1/8 turn.

7. Restart the engine and return to step 1. YOU MUST RESET THE HIGH SPEED NEEDLE every time you adjust the low speed needle.

8. Repeat this process until the engine idles reliably, and doesn't hesitate going to full throttle.

The low end must be adjusted slowly. It is extremely sensitive, and its very easy to go right past the sweet spot.

Unless the engine has had a few tanks of fuel run through it, don't even bother with the low end needle. Wait until the engine is broken in. Once you get the low end dialed in, you'll never need to touch it again. BTW, the factory settings are close, but rarely perfect. That's why low end tuning is something everyone should practice, but few seem to do well.

The color of the oil on the plane after a flight is a good indicator. Lots of clear oil with white smoke while flying indicates a rich engine. As the smoke gets clearer, the engine is running leaner, and temperatures increase. Brown color in the oil indicates the oil is getting hot enough to start breaking down. A very light hint of brown is okay. Thats why having a little castor in the fuel is good. It won't break down as quickly, and will protect your engine better against a lean run.

Brad