DLE 170 dead cylinder and piston

[thurmma]

Hello Everyone,
Back to issues with the DLE 170. This time it is dead Had everything running great and was having fun flying some IMAC when I was on an upline, not any longer than usual and no rolls or snaps it started to die. I tried flipping the throttle a couple times but, no response. I pushed the plane over and dead sticked it in, glad I had the altitude that I did when it died made the landing uneventful. I grabbed the prop to turn it over and it was very difficult to turn it over so I stopped trying. It was not hot at all, as a matter of fact it was nice and cool. When I got home I tore the engine down and the pictures below tell the story of the right jug as viewed from the front of the plane. I pulled the left jug off and there was just one score in it, dead center on the exhaust port. Other than that it was fine. Plenty of oil residue everywhere and a lot of oil residue on the bottom of the plane.
Any ideas as to why this may have happened? I was running Stihl Ultra mixed 32 to 1.

 

[49dimes]

There is an area on the exhaust bridge on the left side about the middle that suspects debris passed through and reeked havoc. You look at wrist pin retainers to see if they are intact and not broken? Or maybe you had a stroke (pun intended) of bad luck and sucked up a hard foreign object.

 

[thurmma]

Wrist pin retainers are all intact. After having one break on a 3w that was the first thing I uspected As far as debri goes, I don't see how that could have happened because the plane had been flyngnfor about 5 minutes before this happened and was running great. It makes me real leary of putting any new parts in it without knowing what caused the issue.

 

[49dimes]

How was the engine loaded (estimated throttle setting and prop used) when the engine encountered the problem?
Personally I don't see any evidence of any kind of heat related failure. Did you look at the reeds and see if they are not broken/chipped? Really looks like something got passed through other than oil mix and air.

 

[Pistolera]

Looks like foreign object damage to me. That's a heck of a bite outta the piston too. Assume the ring is still intact...no missing section?

Stihl Ultra is good oil. I ran that for several years at 50:1.....until I got a great buy on a gallon of Red Line. But my engines (DA120 and DA150) both ran and looked great on Stihl as well.

 

[yakken]

Is the piston on correctly. Ring gap is not on the exhaust side is it?

 

[yakken]

I see that its not now.

 

[thurmma]

Assume the ring is still intact...no missing section

The ring is still intact, just missing stuff where the rest of the damage to the piston is.

 

[thurmma]

I talked to Ken Crane and he thinks it may have went to lean just long enough for the piston to start to let go and the rest happened from there. He said that there was a known issue with fuel delivery to the front cylinder, which is the one that got tore up, and they would go lean with no warning.

I know most of you here may not have followed some of the issues this engine has had from about the 4th gallon on but, one of the issues was the engine going lean while warming up for the 3rd flight of the day. I would back out the high speed needle a full turn and it would calm back down and run fine until about 3 or 4 minutes into the flight, then it would go back to super rich. I figured it was the carb so I ordered a DA170 carb and it had appeared to fix the issue until this happened

I will say this, when I took the jugs off the jug that died wasn't as tight as the other one. I am wondering if somehow after it got warmed up an air leak got introduced at higher rpm? Don't know but, I do plan on putting new pistons and jugs on it. When I put it back together I will be torqueing them both down to the same specs once I find them

BTW, I do have a GP-176 on the way Will be interesting on RE3's I am sure!

 

[yakken]

Why put two jugs on?