Hey guys. I'm experiencing some strange behavior with my DLE 55 powering my Pilot Yak that I hope someone can offer some insight for. Please excuse the length of the post, but I want to make sure that I'm as complete in my description as possible.

The engine has about 2.5 gallons through it, and I'm still using the break-in prop (Xoar 22x8). I'm using genuine NGK CM6 spark plugs in it, and only use filtered 93 octane gas from brand-name gas stations at a 30:1 mix with synthetic blend low-ash 2-stroke oil. I have clunk filters (screen-type) in both my filler can as well as my tank, and have a an inline fuel filter between the tank and the carb (I mention this just so everyone has the full story, not because I believe it's better or worse than how other folks run theirs). When I first installed the engine, it fired after a short amount of effort and proceeded to run fine. I put 15-20 flights on the plane without incident over the course of a few weekends, the engine running very well during this time.

Then one weekend I brought the Yak back out to the field and tried to start it, but had a VERYdifficult time getting it running. It would pop and start, but then die after a few seconds, or when I tried to transition it. A few of the folks at the field who are more experienced with gas engines than I am (this is my second one, the other being a DLE 30 that has never given me a problem right from the box) helped me check all the normal troubleshooting steps, and finally set to making some adjustments to the needles to try to get some results. After a bit, we were able to get it running pretty reliably and I flew it the rest of the weekend without incident.

The next weekend I brought it out and had similar issues, and again, a few folks helped troubleshoot and we ended up adjusting needles again. Once again, we got the engine running, but now it was so rich that it was developing very little power and never cleared out, even at WOT. Still, I flew it the rest of the day without further incident.

The next morning I came back out to the field and decided that I was unhappy with the extremely rich running (plus the expectation of impending fouled plugs, the inefficient break-in of the engine, and the threat of a dead-stick) and returned the needles to the factory settings. Voila! Immediately, the engine fired, ran great with a burble up to ~40% throttle, and a good clearing out, transition, and power production above that. The rest of the day was flawless, and I was exceptionally pleased.

That brings us to this weekend. I brought the plane out, filled it, choke on, ignition on, throttle at idle. 5-10 flips and the engine pops. Idle off and another few flips and the engine fires and idles for a few seconds before dying. Choke, flip, pop, choke off, flip, fire, run, die. Rinse and repeat. It really sounded like the engine was running out of gas, but we couldn't find any reason for it. There was fuel in the lines and there didn't appear to be any air leaks. I checked the fuel screen in the carb and made sure it was clear, and also swapped the spark plug for a new one just in case. We verified the needle settings and then richened the low by 1/8th. The engine still wouldn't idle, so I drained all the fuel out and filled it with fuel from another can, thinking that I may have a batch of bad fuel. Suddenly, the engine fired up and idled, but died when I tried to transition, so we richened the high speed needle and the engine was now running and transitioning, albeit rich on the high side.

I flew the plane around a bit, happy that it was running but unhappy at the power production at WOT. I had grown used to its usual power output, and this felt very sluggish (because we had the high speed needle very rich). I landed the plane and set both needles back to factory settings (AGAIN) and fired the plane up. It fired and ran perfectly (AGAIN). Low speed, high speed, transition, idle, wide-open throttle, the whole bit. The power was back to normal and the engine sounded GREAT.

Must be the fuel, right? Well, I figured the only way to be sure is to drain the fuel that was in the tank and put my fuel back in and see how it runs. So I did this and flipped the prop and the engine started right up. I sat there a few seconds, waiting for the engine to die, but it ran beautifully, transitioned great, and produced the normal power output that I had grown used to. I flew it for several more 15-minute flights to ensure that everything was good, and experienced no further issues.

So, once again, I've gone to the field with stock needle settings, experienced engine problems and made adjustments to just about everything we could think of to troubleshoot the issue, got the engine limping along, only to end up exactly where I started (stock needle settings and my own fuel) at the end of the day with an engine running like a top.

Jeez - at this point I have no idea what to even think. There seems to be some sort of weird voodoo going on and I'm thinking of checking the city archives to see if the flying field is built on an old indian burial ground or something. I'm hoping that someone has some idea of what might be going on.

Thanks all.