Piston #2 let go

[MarkWebber]

2 engines, same trouble.

1st engine was an OS 50sxh nonhyper. For routine maintenance reasons, I replaced the piston and liner. Didn't really look too bad, but whatever. While breaking in the new assembly with about 5 tanks into it and still running a bit rich, it just began to lose power then "pop", hole in the piston. Enough damage to everything else to make it worthwhile to buy new.

2nd engine is a OS 50sxh hyper. Basically, the same results as the first unit. Still running rich then 'pop".

Raptor 50, Wildcat 15%, enya #3, CY muscle pipe all while hovering in normal early-late spring conditions. All fuel lines had been replaced previously. Prior to the first piston replacement, this heli was flying fine. I only replaced the piston because I got this heli used and didn't know exactly how much time the engine had on it.

Thoughts?

Thanks,

[ferret80]

are you using a piston lock tool... i have a friend who used a piston lock tool and they are shocking.. putting a huge amount of load on the crown... use a crank lock tool or do what i do.. use a bit of rag, pull the head off, place the piece of rag ontop of the piston, place head back on and tighten the nut up...

if you dont use a piston lock tool, i cant help you.. hope this has been helpfull

[MarkWebber]

No piston lock tool used ever.

Here's what it looks like. Just disassembled it this a.m.

[DavidH]

From the pic in my opinion looks like the mixture was on the lean side.

David

[Hotwings]

way too lean, :bomb:

[MarkWebber]

I agree. The last one looked the same.

Now, what might be causing it to lean out in the air like that? The rpm never picked up before it went. Another pilot I fly with was with me the day before the incident. He too was surprised that it let go like this because I was still running it rich. It was still 4 stroking quite a bit.

New parts are on the way and I don't want to duplicate this :arggg:

Thanks

[ferret80]

MY opinion.. throw the motor in the bin and buy a new one.. the engine has been under alot of stress by the looks of things... no telling what the rest of the engine is thinking (stress and fetigue)... bearings ? what fuel and plug ?

[MarkWebber]

Anyone have one lean out while in flight like this before?

Thanks,