OS .40 FX - A Tale of Woe

Good Evening. A couple months ago I bought a used OS .40 FX I found on
the Net, and installed it in my Tower Kaos. It ran fine the first month
or so I have been flying the plane...until this afternoon! I couldn't
even get the engine started for my first flight. When I cranked the
prop, it took several tries to get running, and when it finally did
fire, the engine ran for a second or so, then abruptly stopped. I heard
a sharp metallic noise when the engine stopped, and it seemed as if the
crankshaft froze on the spot. I removed the glow plug, and eventually
got the shaft cranking again, but it didn't feel smooth; I felt a bind
just before the piston got to the top of the engine. I haven't yet had
a chance to remove the engine and disassemble it to inspect the inside.
I don't know how old the engine is, but I would imagine it's out of
warranty already. Could these problems mean that either the bearings or
the crankshaft are shot? I don't know if OS carries any replacement
bearings. Any advice would be appreciated.
Harry Sanchez
Reply to
Harry Sanchez
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I wonder if anyone has experience with the infamous "peeled liner". Where's Mr Akimoto when you need him? I' probably get A RAZ for that. mk
Reply to
Storm's Hamburgers
You've already figured out that's not good. :o(
It could be anything.
FX engines had a problem with "peeling liners" once upon a time. You might have gotten one of the bad ones.
All the parts are replaceable, but somewhat expensive (if purchased from OS).
Take it all apart, examine everything carefully, and you will probably see what's broke. Piston? Liner? Connecting rod? Bearings?
There are some good Chinese engines (Thunder Tiger, GMS) that may cost less new than replacement parts. You could probably get $20 trade-in from Randy Linslato's company (RJL) on the OS and acquire a GMS .46 for $60 or so. (I'm not sure the offer is still being made. Check any of the modeling magazines or google around.)
Reply to
Martin X. Moleski, SJ
On Fri, 21 Apr 2006 09:57:06 -0400, "Martin X. Moleski, SJ"
Different China, different quality, Marty
The Thunder Tiger engines come from Taiwan and are every bit as good as OS, at a lower price. No peeling liners, either. Not knocking the GMS - my .47 is lacking in cosmetics compared to the Japanese engines but still runs strong after years of use. Shared one flaw that seems pandemic among engines from the PRC - apparently there is no source of decent O-rings there. One way to buy good engines on a shoestring budget is to buy 'sick' GMS or Magnum engines at a swap meet and replace all the seals.
Reply to
Abel Pranger
A full array of parts for your .40 FX is available through Great Planes here in North America either via O.S. customer service, Tower Hobbies, or your local hobby store. I have an old .40 FX that I bought used last year and it's been a terrific engine so far.
It must be disappointing to have your .40 FX sieze up on you like it did, but there was probably a reason whoever sold it to wanted to let it go. If you spend the time and money to get it rebuilt, you'll undoubtedly have a good reliable engine. As previously mentioned, you might be ahead of the game financially if you simply sell it as a "parts motor" on EBay and buy a Thunder Tiger Pro .40 to replace it.
Reply to
Ed Paasch
One thing you didn't tell us was what kind of fuel you were using and what prop. Of course, in my opinion, if you are using a total synthetic oil fuel you can expect the engine to run hot....as for me, and I don't want to stir things up, but I have engines I have had for many years that I have run on a castor blend and they still give great performance. On occasion, when I ran out of fuel at the field and made the mistake of borrowing a tank of all synthetic oil fuel, I had a bad...and hot engine run.... Frank
Reply to
Frank Schwartz
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Are doing replacement piston/liners for that very engine for
under £30 Sterling.
They're not genuine O.S but are completely compatible.
"Just Engines" have a pretty good reputation from
what I hear.
Might be worth a look.
Reply to
I have the same engine OS 40FX bought second hand on a plane, got home with the combo and the crap turned once. I sent it to hobby services and they told me:
"We looked over your engine and both bearings are very rough,piston and cylinder are scored.The cost of parts and labor will be more than a new engine.We can offer you a new engine for $81+shipping and your old engine."
I haven't replied yet because I just bought a brand new SK50A from
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for only US$59.00. Maybe back in the days OS was the only quality engine out there so you had to suck up the high prices, but not any more a lot of manufacturers are building and selling great engines for a lot less IMO. If US$81 + shipping sounds good for you, then send it to hobby services. Good luck
Reply to
NO, but I think most O.S. engines are fine, even good, except the known "peeling liner" problem. For what it's worth I don't think moisture can go through plastic so lets not whip this thread into horse pulp. :)
Reply to
They work great, break in great, easy to use, good power. But they don't last very well. I have never had a liner to go bad, but have had bearings to go out. Lots of bearing problems reported.
Reply to
Sport Pilot

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