The process begins at the point of fuel mixture that causes the engine to just break out of four cycling to two cycling. It then says to slowly lean the mixture as long as the engine can hold the new setting while giving the line a little pinch to assure that the engine gains rpm. The pinch test assures that you are never running the engine peaked or leaned out. They say this should take approx. 1/2 hour of running time until the engine can hold a mixture setting at the point where when the needle is leaned to peak and the rpm remains constant even during the pinch test. If at any time you pinch the line and the engine looses rpm immediately richen the mixture 1/4 turn and begin leaning again. You may find that the process takes even longer. I would say thirty minuutes should be the minimum running time before you find the actual peak rpm point. Remember you are dealing with cast iron and hardened steel surfaces with the ring and cylinder not aluminum and nickel. The object is obvious. Don't ever run the engine more lean than it will hold it indefinitly. Never run the engine more lean than peak rpm. These engines are capable of running lean until they burn up rather that just leaning out and quitting.

Personally I do not run any of my engines any more to the lean side than the point where I can pinch the fuel line and get a 2 or 3 hundred rpm gain no matter how used they are and more like 5 or 6 hundred rpm to the rich side for the first few flights. The pinch test is a very good technique for tuning all glow engines once you get the "feel" for it. You will also find that your Tigre will produce nearly the same power at a fairly rich setting and smoking fairly heavily rather than pushing it to the lean limits. If you make sure that you stay to the rich side your engine will last hundreds of hours.

Take care, Cliff