Most glow engines I know of only have a low end needle valve and a high end needle valve. I adjust my mid-range through the low end needle valve. Some people in this hobby don't know how to do it correctly nor have they ever heard of getting the mid-range adjusted IMHO.

To get a perfect low end/mid range, get your glow engine started and run it at full throttle ( Thats to clear the motor ) then go half throttle. VERY CAREFULLY, adjust the low end until you hear the engine smooth out. (I use a wire clothes hanger and beat a flat tip on the end if you don't have a very long thin screw driver. That way my fingers stay away from the prop and can keep my hands at a safe distance)

Keep turning low end needle clockwize until you here it slightly decrease in power ( That means you are too lean ) so turn it back counter clockwize until you get that fast nice smooth RPM, then turn it 1/16 to 3/16 turn more, then leave it. Now throttle down for a bit and move the throttle at a good pace to full throttle.

Now it's time to adjust the top end. Once you have the top end set the way you want it. Tilt the nose of the plane up, if you hear the engine rpm slightly increase, that's good. Me I try to find that happy medium that I had already mentioned.

Now the real test after doing what I suggested.

Let the plane idle for about a 2 minutes, now slam the throttle forward. You should get a very slight hessitation, then your engine should go full power without coughing or quiting.

Ever since the President of my ex-club showed me how to get the settings right on glow engines, I haven't had to re-adjust my low end or mid-range. Make sure your plane is properly secured when adjusting your carb. It's best to make all the adjustments on a engine stand if you have one, but if you don't you can still adjust the engine while it's in the aircraft. Just be careful.

This procedure works for all 2 and 4-stroke glow engines.

Pete