PICTURE D shows the Mix screen after we have adjusted the mix, but initially just make this a straight line with  100% values  at the endpoints. During the test running, you will begin to fine-tune these adjustments. On the mixture side of the MC Carburetor, you will see two marks in the aluminum carb body outside of the brass body. There is a slot scribed into the center of the mixture control, as shown in PICTURE E.

 When initially setting up the carburetor with the P-Mix, set to 100% on the endpoints and adjust the linkage and the travel adjustment on Aux. 4 so that when the throttle stick is at full throttle, the slot in the end of the mixture valve aligns with the forward mark on the carb. This is the full rich position.  At idle, the slot should align with the rear mark on the carb body. This is the full lean setting and just a starting point. Initial test runs may show that these positions need to be adjusted.

Before doing the first test run, there are a few things to note. With this setup, instead of mechanically adjusting a high-speed needle valve or a low-speed needle, the mixture is adjusted electronically in the transmitter. In addition, since the mixture servo is on the Aux. 4 channel, turning the Aux. 4 knob adjusts the position of that servo. Keep in mind that this will adjust the mixture at all points. If you richen the knob, it will richen the mixture at every throttle stick position, not just the high end. This is actually quite useful when adjusting the engine, particularly when setting the mix values at the different throttle stick positions.

Now it's time to do the first test run. Here is where you may have to adjust the mechanical position of the mixture arm on the shaft. If the engine initially appears to be

way rich or way lean, shut off the engine, loosen the set screw on the mixture arm and turn the center shaft to either lean or richen the mixture. Try a 10-degree adjustment initially. Start the engine and see if you're getting close. Don't try to make big adjustments electronically until you get the mixture arm located correctly.

Continue to make this adjustment until the engine will start and idle sufficiently. Once this happens, with the P-Mix screen up on the transmitter ready to adjust, bring the throttle up to the next point on the curve. That's point 1 in the 10X. By turning the Aux. 4 knob, check and see if the mixture is lean or rich. If it's off, adjust the P-Mix curve at point 1 up or down until the mixture is correct, then move the throttle up to point 2 on the curve.

Continue this process until the entire throttle range is adjusted. Take your time, get a helper to hold the model and be careful not to overheat the engine. Sometimes it's a good idea to shut down and let everything cool for a few minutes, then go at it again.

It's better to keep the first few points on the idle side of the curve slightly on the rich side. This will give you an engine that will drop right down into idle, giving excellent braking on the downlines.

Flying at this point will tell you if you need to make any adjustments. We typically fine-tune things for sev­eral flights to really get the mixture perfect, particularly if the engine is new. Not a whole lot different than a "normal" setup. However, the ground setup, if done right, should give you an engine that will run reliably enough to start flying.

This process may seem complicated when you first begin, but it soon becomes routine, and is in many ways even easier than trying to adjust a "normal" carb.  You don't need holes in the cowl for needle valve access, and once you get the rough adjustments you won't need to shut off the engine to adjust it.