I'm new to 4-stroke engines but not new to glow. Does a 4-stroke engine follow to same rules as a 2-stroke when it comes to lean and rich. For example, when at full throttle and you pinch the fuel line, there should be a slight increase in RPM, if there is no increase in RPM then the engine is too lean. Are 4-stroke engines the same?

Theoretically yes, but with the lower RPM that 4 strokes run it's hard to hear the difference. You'll save yourself a lot of time and frustration by getting a tachometer. Use the tach to set the engine on the rich side of peak, then use it to set the idle mixture at peak. Then go back and set the top end 300-400 RPM rich and go fly. The tach will turn an hour long trial and error process into a 10 minute job, and it also comes in handy for diagnosing engine troubles when you think you have them.

Also, with a four stroke you want to see a nice trail of smoke coming out of the exhaust when the plane is in the air. This is a visual indication that you are on the rich side.

I do it like 52 Larry does it

+2

Thanks for the input, both ways. Let's assume I did use a tachometer, how do you know what the high end and low end RPM should be?

Check the manual that came with the engine. It should tell you. I find if I get my old Saito too lean I risk a backfire and the prop ejected off the airplane along with prop washer, nut, and lock nut.

Hi!
You set a four stroke the same as with a two stroke! You listen to how it sounds.
No pinching, no tach, no smoke trail, just using your ear and adjusting the needle! Done it that way now for over forty years.

+3 on how 52 Larry52 does it plus if its getting too hot its probably too lean . If you have somebody at your club that is good with four strokes it would be a good idea to ask him if he would help you tune it and then once it is set leave it alone , espially the low speed needle .. They usually hold their tune fairly well . Good luck .Four strokes are great engines .

For the experienced, any of the alternate methods mentioned above will get you there. But they are all just an approximation of getting it right. A smoke trail only tells you that you aren't burning up all of your oil in the combustion process. That's good enough to know if your engine is safe, but it doesn't tell you if you have the mix set for max power. The ear method or the pinch method will get you close, but you don't actually know how close. With a tach, you can see the RPM rise with each click of the needle valve, then stop rising, then start to drop as you get too lean. It will guide you quickly to the exact spot where the engine is at the optimum mix, then allow you to richen it up for flight precisely. The amount it needs to be richened depends on how much the engine unloads in flight, but 400 RPM is a good starting point. Setting the idle is the same; get your lowest reliable setting and then watch what changes happen on the tach.
Besides making the process easier and more precise, the other benefit is repeatability. Engines need to be adjusted for weather, so if you know you engine needs to be 300 RPM rich to run right, it's a 1 minute process to find the peak setting and then richen it to where it needs to be. You'll get it right the first time every t l time once you know what your engine needs.

Listen to the engine and pay attention to the exhaust while you're searching for the highest rpm setting. That setting is too lean. How much too lean? Go rich a couple of hundred rpm and look at the exhaust. It'll show a touch of "smoke" or it won't. Glow fuel engines get some of their cooling (the important cooling) from exhausted unburned fuel. If you don't see "smoke" there isn't any, and the engine is running too lean.

We always get the engines too rich and work from there to keep from running them too hot. Using the tach you can work from too rich up to lean (the highest tach reading) safely and keep from going beyond "a little lean" into too lean.

The tach is about the only way any newbie can safely needle a 4 stroke.

Forget about discovering what the low end RPM is using any tool. You discover it by trimming your throttle on the TX to a speed that won't pull the model forward when sitting, and prove it by test flying. You discover the best high speed setting by testing your findings from the description above by test flying also. By looking for some visible exhaust.

Without a tach, a newbie is wasting his time and whatever he spent on the engine.