Could someone please take the time to explain proper technique for tuning an engine. Either by "pinch test" or by whatever method may work for you. I hate quessing.

Thanks

Most engine manuals will tell you how to tune their engines and should be followed just in case a warranty issue arises. Saito, O.S., Thunder Tigre, Super Tiger, YS, Evolution and others all have downloadable manuals on their web sites if you need one.

If you have a speific engine in mind, that will also help.

Generally, after break in, you lean the high speed needle to max rpm then richen the high speed needle about 300 to 500 rpm so you do not run lean in the air. A tach is recommended for this procedure and for a four stroke, is absolutely needed as hearing rpm changes on 4-strokes is difficult. A 2-stroke is easier to hear the changes.

Once you have the high speed set, you work on the low speed to get a smooth and rapid transition from: idle to mid-throttle and idle to max throttle. The reason for idle to mid-throttle is on most glow engines, the high speed does not really kick in until mid-throttle and above. The exception to this rule is YS engines since they use a regulator for fuel injection above roughly 2200 rpm so the low speed only works for the transition from idle to regulator and the regulator is then adjusted from there to max throttle.

On most engines to richen either needle it is turned counter-clockwise and to lean it you go clockwise. On an airbleed carb (usually on smaller engines .15 to .30 range, usually) it is usually the opposite.

One other item, the low speed needle is usually more sensitive than the high speed needle so when adjusting the low speed you start with 1/8 turns.

Thank you, that helps. I was speaking in pretty general terms but pretty much referring to the 2 stroke, 40 to 60 size or so. Your information is greatly appreciated.

Thanks again.

In addition to what Bill said, I always point the nose of the plane in the air for 5-10 seconds. This tests both the mixture, to make sure it's not too lean, and that the engine is able to properly draw fuel at extreme climb levels. If the speed increases when you raise it, you know it's not too lean, but still could be too rich. If the speed decreases, either when you first point it up, or after a few seconds, you know the engine is too lean, or is having fuel draw problems. If this happens, immediately put the plane down, on the ground, and richen it a bit. Note, I also consider no speed change in the nose up test to be a "too lean" indication. I want my engine a bit rich at takeoff to eliminate the possibility of it going lean later in the flight.

A quick followup on safety. The nose up test should only be done when you have a firm TWO HANDED grip on the plane. One hand somewhere on the rear of the fuse, and the other near the front of the plane, but a safe distance from the engine. If you're doing this by yourself (and I don't mean that you are at the field alone), leave the transmitter on the ground.

Yeah, hold on to that sucker like a five pound bass, and don't kick your transmitter....

I use Chuck's methos, and it seems to work out best for me, for the high speed needle at least. The low speed needle or air bleed screw I adjust depending on idle and transition.
Dennis-