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Old 04-23-2008 | 11:52 AM
  #9  
da Rock
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From: Near Pfafftown NC
Default RE: engine break-in

OK then, let's focus a bit closer on having a rich setting in the air. We've had two very similar descriptions, but let's get just a touch more detailed.

Every first flight of the day should start the same. You need to feel out the needle setting to set the high speed needle for the conditions on that day. The following assumes the engine lowspeed needle has been adjusted properly.

Engines start really well with the throttle closed completely and then opened just a touch. Throttle sticks are ratcheted, and about three clicks seems to work with most. When the engine starts, let it run at that throttle while you move stuff out of the way and move around behind the airplane. Remove the glow starter and smoothly advance the throttle to max. Now, the important stuff.......

Slowly back the needle a click at a time. The rpms may increase. Or not. What you're wanting to see is the engine obviously going rich. As soon as you see it, you can start the needle back in. What you've just done is to establish positively that the needle setting is starting from a safely rich needle position. Didn't take but a couple of seconds to do.

As you click the needle in, obviously the rpms are going to increase. At some point they won't continue to increase. Keep clicking and the rpms will start to fall. Instantly go back some. "SOME" ????? JEEZ, this is pretty sloppy advice, isn't it? Well.............

What you want to do is get familiar with your needle response. And you're doing it right then. As you moved the needle from full rich to that max rpm setting, you had the opportunity to observe how much you had to move the needle. You did pay attention, right? And from that FLAT OUT needle position, you kept clicking until you heard the engine sag a bit. And you were carefully noting how far you turned the needle then, right? So "some" shouldn't be much mystery for you. Crank the needle back to where the max rpm was. But now keep backing a few more clicks. You want to adjust the needle so the engine is running safely rich on the ground. And if you stopped the needle setting where the engine was at max rpm on the ground, the setting would be too lean in the air. The advice is still too sloopy, isn't it. Good reason for that.

You need to take note of what you've just felt the needle do, and then observe how the engine/plane responds in the air. You're learning how your engine needle setting handles. And ain't nobody can tell you how many clicks are right for your engine. Not even the manufacturer will know. Or any field expert (although they'll have no problem giving a number, most times) for that matter.

Now, there is still one more part to this song and dance. You need to look for exhaust. With 2cycles, you will almost always be able to see some. If you do, kewl. If you don't (and there will be few days when you won't when the engine is rich enough) then pull a hard loop or somesuch and listen to the engine. It should pull ok and not sag. Truth is, after you've gotten comfortable with this song and dance, the needle will be close and you'll be able to feel how the plane handles on takeoff and climb out and know if you want to land right away.

Whenever the takeoff and climbout and whatever doesn't feel right, or you think you should be seeing exhaust and you're not, land the sucker and give the needl a couple of clicks. Here again, "some" clicks are how many you'll want ..... grin......

Once you have done this song and dance a few times, you're going to have a really good feel for how many clicks you'll need throughout the dance. But that doesn't mean you can blow it off after some number of outings. Because our engines are fairly sensitive to the atmosphere they suck down their little throats. Way more sensitive then we are. We have almost no feel for humidity, temperature and atmospheric pressu