Surging engine

My guess would be either fuel foaming, or a particle in the fuel tank that intermittently gets sucked onto the fuel pickup. Or is your servo linkage surging back and forth?

Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

Also check the throttle servo screws. Make sure they haven't loosened up. I had that happen on one plane. Drove me and several "gurus" nuts until a newbie said "Is the servo supposed to move around like that ?" - from the mouth of babies. {:-)

It was leaning out. That could indicate an obstruction in the fuel system. It could've been as simple as a needle adjustment (richer).

I didn't notice any movement of the servo, but I wasn't especially looking either. I think I'm going to go with a particle in the fuel tank. Sounds like it's time to pull the tank and tear it down and see if I can get it cleaned up. I can also check the servo while I'm in there.

The Evo engine sure starts and adjusts easily, but I wonder if the ease of adjustment leads to some over-tinkering of the needles...

Thanks, Steve

If you have a brass tube in the tank, check to see if it is leaking air.... fuel eventually will corrode the tube and cause minor air leaks that can make the engine run erratically and keep you from completely emptying the tank at the end of the day.

Actually, that was how I found my tube did have an air leak. I could not pump it dry when it was time to go home.

az21 .