Second hand engine question

[ferincr]

Hi, I never bought a second hand engine before, so I'd like to know what can I expect from it.
If an engine has been sent for an overhaul (piston, rear bearing, liner change) does it means that I can assume that it's almost as good as new? or there are any draw backs from this that I should consider before buying?
Thanks for any comments,

[Laurens]

You can expect some nasty surprises. At least thats my experience with almost half of all the engines I've bought secondhand.

[ferincr]

Well, it seems like nobody else has anything to say about second hand engines:thinking
Since the only reply is not very positive I'll take it like it's the general consensus:dontknow:dontknow:dontknow

[Rogan]

If they don't show you a picture of the port and piston, then it's probably fishy.

If they say only run for X hours, they probably mean one season. Etc etc etc. A lot of reading between the lines is required.

[Danyboy]

Here goes the story of a friend of mine...

He quit Heli-flying about 14years ago, to go flying in planes himself. But with all the bureaucracy and lunacy getting more and more fancy, he decided to quit flying and come back to what really counts: Heli Flying... :)

Problem is, he got rid of all his stuff...
(Honestly, my opinion is, he better did, most people do not know what they're missing out with modern stuff until they've set up a tail once without and then with something like a 401...)

Now to start again, he thought he'd catch a good deal...
UniStar60 mechanics (Graupner, quite common) with all the support-equipment, together with a MC-22-transmitter, which he saw in use with me and was convinced. According to owner, all the stuff was sitting for two years on the shelf doing nothing (alarm bell goes off)...

For me, it was a so-so-deal, even if the heli was crap, there'd be parts to salvage, so he'd get an outdated transmitter (the old version, they've gotten a new software since, along with synthesizer) for just a bit over the shop-price.
What made it a bit fishy for me, is the overall condition of the heli along with the programming of the transmitter. Most parts of installation on the heli were really thought out and nicely done, but then again, there was some primitive and ugly improvisation. Like with the RX-Battery, the cells weren't connected by a proper lead oder the original tabs or even those nice and golden-shiny bone-connectors, the were connected with servo-lead. And it wasn't really soldered on, more like smoldered... RPM-Pickup (unfortunatly no governor) not cable-tied, double-taped, or something similar, but simply hot-glued. Not nicely glued, but simply a splotch of glue allover the poor thing...
Programming of the transmitter was obviously done by someone, that did not really know how it works, but rather did find out, that he could move switches and that made a response on the heli...

Whatev'... It still *is* a heli... Programming (to me) is a breeze, and after one hour, we were ready and good to go.

Everything setup and doublechecked, went to the field, engine started nicely. Spooling up, found mixture too rich, which is no wonder, since we used a high-quality fuel and before there was only cheap 0%-Nitro... Ok, adjust the needles slightly, up again, much better, some hovering, almost everything spot-on. Since it was first-flight, nothing bigger than just hovering and trimming. Two times interrupting and tweaking needles to go even leaner, since it still was awful rich.
Second tank, some more hovering, then to check the curves some short power-climbs/zooms, had to tweak a little, but overall worked ok. Some hovering manoevers, just wanted to start figure-8's when the engine just quit as if someone did throw the switch. Ok, tank empty already (though not really empty, just low, no RPM increase due leaning occurred prior to shutdown), refueled, tried to restart. No good. First, I couldn't turn the engine over, so I thought about hydro-lock. Friend had a closer look, found that now, he was able to turn the engine without resistance...

Inspection of the engine showed:
Corrosion on crankshaft and piston rod. Bearings seemed ok but also showed first signs of corrosion. Piston rod was broken in two. The break was close to where it sits on the crankshaft and immediate surroundings showed lots of corrosion.
Parts needed are still cheaper than a new engine but one thing learned:

Whenever you buy a second-hand engine, take at least the rear plate off before first flight. Better to replace some slightly suspect parts straight away than to try to squeeze some flights out of it just to find out that you crashed the heli because of the failed engine.

With us, nothing happened to the heli - I was only at hip-height with training-gear on - but I can very well imagine what could happen, because normally, those suckers quit on you when you least expect it and when you least can use it...

So in short words:
Check for parts availability and pricing, if the price of the used engine is low enough so you can buy some parts before exceeding the price of a new one, I'd say it's okay.
Different story though if you're buying from someone you know well and trust... ;)

Cheers,

Daniel

[HeliEddie]

I have purchased two engines used from people online. First was an OS 91SZ-H. Reported to have less than a case of fuel through it. Seller provided pics of the engine, including the piston and port. Looked great in pics. Got it and it was exactly as described. Practically new. Tons of compression and tons of power. Still have it in my Raptor 90.

Second engine was an OS 32SX-H Ringed. Seller stated the engine had low time and great compression. He provided pics of the piston and port. Also stated it came with a TT muffler. Muffler ended up being a Mavrikk muffler (I didn't care). Put the engine in my Raptor 30V2. Seems to run fine so far.

Your best bet is to always ask for pics of the piston (and ring if applicable) and the exhaust port. Ask how much fuel has been through the engine as well. You always take a risk buying used stuff, especially engines.

[Bigbobby]

I have bought a few engines. One was completely toast (ring piston liner and bearing were wrecked) but the previous owner coughed up the money to replace them. After the rebuild, I had a new TT50 for about half the price of a new one.
I also bought 3 x 91 SZH motors for the same price as a new one. One went straight in to a Stratus and runs like a dream. The others need a ring and main bearing before use.
I never pay more than half after including a ring and bearing. If there aren't any available second hand that meet this, I buy new. Its a lot easier and less stressful.

[ferincr]

Thanks guys,
I'm still looking, it seems like those OS 91 come in waves, there is alway someone offering one or two of them so I'm waiting for "the one" to show up.