C/LCombat B
reak in is back. There is no ques- tion that better materials and manufacturing make the newer engines a whole lot better than the oldies. I can remember spending two to three hours running in an engine with an iron piston and a steel sleeve. Start it blub- bery rich and run for two minutes, then let it cool off and fire it up again for two min- utes more.
More recently, many new engines have an aluminum piston running in a chrome or nickel plated brass or aluminum sleeve and seem to run well right out of the box. Just run a tankful of fuel to make sure the plug is good and then go fly.
That really isn’t a good idea though. The parts may fit perfectly, but even if they do, they change shape when they get hot. Every time a new engine runs, the parts change slightly until they finally settle down and everything runs better.
We recently got some of the new Profi 2.5 F2D engines, redesigned a bit for the 6mm muffler rule. The small muffler outlet makes them run hotter, so some changes (don’t ask me exactly what) were made so it ran colder. A new break-in procedure recom- mends running for about 30 minutes at a fast 4 cycle with a light prop around a 6x3.5 or so (Profi specifically recommends a 156x88mm prop).
Now put it in a plane for a few flights just
doing level laps. Then try a few flights with maneuvers. If there are any signs of over- heating such as being very hot on landing, making crackling or popcorn sounds, or un- even running, go back and do a couple more level flights running richer. After a number of flights it will settle down, stop the uneven running and hold the needle valve setting on consecutive flights.
Now take out one head gasket and repeat the process. The engines come with as many as six gaskets installed to prevent you from abusing them too badly. Likely it will run more unevenly again and the needle valve will have to be adjusted between flights. But it will settle down again after a few flights so you can take out another gasket. Keep in mind that you will want to pinch the fuel line lightly a few times to get the en- gine to speed up before changing the needle valve setting. When fully broken in, it will settle down at the flying setting without ad- justing the needle valve.
My Ukrainian flying buddy recently talked me into getting a couple of the new Zalp K engines. They run even colder than the Fora. We could barely get it started in 50-degree weather. It took about twice as long as the Fora to break in. A new piston material tends to keep growing from the heat cycling.
We got it off a bit lean on one flight. It didn’t get blistering hot, but the piston tightened up in the sleeve and we had to go back to several rich flights to loosen it up so we could continue the break-in process. Now it’s mostly broken in. Still one more gasket to
32 JUNE 2014 PHOTOGRAPHY: PHIL CARTIER
The newest Zalp for 2014 has a revised and sturdier case (above). It looks a lot like the Fora 2.5, which is not surprising since one of the original Fora designers builds the Zalp. The front bearing is located by a locking ring. The ring should put all the crash loads on the cheaper front bearing. Note the nice, big muffler with a 6mm outlet. Both the Zalp and the Fora have the cylinder mounted symmetrically in the case with rear exhaust. The exhaust stack on the cylinder sets the angle for the muffler. Larry Wilks tries to fly his Gotcha SL(below) away from his friend Ken Cook flying a Jeff Dawson Fast ship (slowly, of course). Ken managed two cuts to one to make up for his worm-eater crash. The site in Hershey, Pennsylvania featured thick, soggy turf so several pilots survived straight-in crashes with no damage other than the prop.
by phil cartier You can reach Phil Cartierat 34 Sweet Arrow Dr, Hummelstown, Pennsylvania 17036, or via e-mail at
philcartier@earthlink.net
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