OS91 HZ-R 3D grenaded itself

[irresponsibility]

I just brought my srimok out from storage (6 months idle) and fired it up yesterday... It has a new engine with roughly 1 and a half gallons through it, and one lean out from a flight about 8 months ago where the fuel clunk didn't do its job.

The engine started up without a problem, flew pretty well (very rich, backplate cool) and I clicked in the high speed two clicks. It sprung to life, leaned out and then quit... The engine wouldn't start and had no compression. Afterwards I looked at the piston and it was heavily scored on the sides, the head was fine. Is this from storing it without preservative oil? Or did this simply happen from lean runs?

would it be better to order and replace the piston and sleeve or get a new engine?

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[ChadL]

Certainly no reason to replace the entire engine. Unless of course you're looking for an excuse Piston, ring, and sleeve replacement is definitely in order. As you know your engine went lean and the piston heated up and scored itself on the sleeve. As to why it went lean....any number of reasons.

I had a lean run on my Srimok once because the fuel fill line to the tank (the line that's typically looped to the pressure release nipple) didn't have a good seal. My only gripe about the Srimok is the fuel line plumbing. One area where keeping it simple would've been nice. One line in for pressure, and one line out for fuel. Oh no, Kasama has to "innovate" everything. Four effing nipples just means four places I can lose pressure. Sorry...rant off. Since my lean run I use fuel line crimps on the four nipples to ensure I've got good seal. I'm not suggesting this is what happened to you, but wouldn't be surprised if it was.

[irresponsibility]

I haven't yet ruled out the fuel system... I only has time to tear down the engine before packing up for holiday travel. I plan on replacing the clunk, filter, lines and doing a rebuild on the engine unless I find further damage. It is quite unfortunate to have this happen, in already pigeon holed into favoring the Electrics due to flying field restrictions... oh nitro engines, why are you so Mich trouble? :p I wouldn't have kept it if the srimok nitro was less of a piece of art. I love this machine.

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[ChadL]

Originally Posted by irresponsibility

I haven't yet ruled out the fuel system... I only has time to tear down the engine before packing up for holiday travel. I plan on replacing the clunk, filter, lines and doing a rebuild on the engine unless I find further damage. It is quite unfortunate to have this happen, in already pigeon holed into favoring the Electrics due to flying field restrictions... oh nitro engines, why are you so Mich trouble? :p I wouldn't have kept it if the srimok nitro was less of a piece of art. I love this machine.

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Yeah...I hear ya. I'm down to one nitro, Srimok. If it were any other brand heli I would've most likely sold it by now. It's such a beautiful machine. Nitro is a love hate relationship for me.

If you're still using the fuel line that's been sitting for several months I'd definitely replace them. Any leaks can cause a lean run. Bad fuel lines, dirty fuel filter, bad check valve, etc. can all be factors in a lean run.