Here's the scoop... OS 61 FX.....I flew, I crashed hard, engine buried itself about 10 inches in soft dirt on impact. I soaked it in nitro fuel for 4 hours and then rinsed all the mud and dirt out with WD40. I took out the glow plug and used an air compressor to blow out the cylinder. I also removed the carb and flooded it with WD40 also. While blowing the air compressor in the glow plug hole the engine would turn over a few times and seemed to turn freely. The needle valve is intact as well, and the low speed idle adjuster is straight and true. Also, the carb throttle linkage turns freely without binding. With a new plug installed it feels like good compression, butnot as good as before the crash. I have not run it yet. My question is, Are there any other items I should check before I re-run the engine?

Thanks,
Luke[8D]

If it was me that puppy would be in pieces on the bench.. which may not be necessary, but at least pull the backplate and 1) make sure the crank didn't break or crack it, and 2) you can look for any dirt you might have missed.

Oh- the engine turned over freely with compressed air in the glow plug hole? That's an ABN engine, it should be a hard squeeze over TDC because of the tapered liner, you may have problems there.. at the very least make sure the crankshaft isn't full of dirt.

Can you tell if the prop shaft is bent or not? Sounds like you did a good job cleaning it. Wouldn't hurt to look inside though.

Looks straight to me. I have had a few others look at it also just to be safe. I was concerned about taking off the backplate due to parts popping out unexpectedly. I will check the manual for the exploded view and then disassemble it accordingly to check for hidden dirt.

Thanks again,
Luke[8D]

Nothing will pop out the back. All thats in there is the back of the crankshaft and the piston arm. You may damage the gasket though. Spares are available.

Well: For what its worth i have in my younger years burried several engines
a foot in the ground doing crazy stuff like learning 3d. I have never destroyed a
engine beyond minor repair. I just take the glow plug out and open the carb
up and flush everything out with hot water real good than use compressed
air to blow it out dry and then oil her down real good and fly it. If it works
great if not i buy a new engine. H*ll its only money.

With the level of cleaning, the only other thing I would do is remove the back plate and clean it out. THen run the engine.

Thanks for the advice and insight.

Luke[8D]

Were you able to resist the urge to spin the prop when you dug it out. If you did not, a little bit of the dirt may have gotten in and scratched the cylinder wall a little. Thats why compresion seems a little lower. I would take off the backplate and get the piston out and clean the bearings really good with denatured alcohol and soke everything in wd 40 or after run oil really good. There was a really good article in one of last months magazines about this. I will look for it and let you know where it is. I would not want to chance my bird on the next flight without being absolutely sure of the condition of the engine.

Take the backplate off, and use a flashlight (if necessary) to look down inside the crankshaft for any signs of dirt. Also, take the carb off the body, and again check for dirt, flush out with fuel or wd-40 or carb cleaner (my favorate).

If you see dirt inside the crankshaft or under the carb, then you should take the engine apart, since the dirt almost certainly made it in to the bearings, and you'll want to flush that out or replace them if there is any doubt.

I saw an engine (not one of mine) that had dirt all the way though the crank, in to the crankcase, and up in the transfer ports, and in to the combustion chamber. The guy who planted it never pulled back the throttle, and I swear that engine tried to keep running underground.

On the other hand, I've burried engines (combat matches result in plenty of lawn darts), sprayed them down at the field with carb cleaner or WD-40, fired them back up and flown them again that day with no problems. Just make sure you close the throttle before impact, that goes a lot way towards keeping dirt out of the inside of the engine.

In fact it's a good habit to get into even when you have a "dead-stick". You might not make it back to the runway, or over-shoot the runway, and this lessens the chances of dirt, grass, seeds, etc from getting into the carb should it nose over, or worse.

This is some excellent info for anyone who has ever crashed. Errr, I mean everyone who has crashed a plane. Proper post mortem engine care is essential to the long life of a otherwise good engine. The info I have gathered here ahs already saved me immeasurable time and money, as well as given me the peace of mind to grow as a RC enthusiast. It's people like those that have responded here that make the RCU community a great place to share a wealth of knowledge. Thanks again for all the insider advice and keep it coming, I'm like a sponge for this stuff!

Luke[8D]

The other day I drove my OS .46 FX into a gravel road under full throttle inverted.. (widn got me on take off...lol) but anyway, the motor was full of rocks, the pipe ripped off and just general gashes from the impact. I took the motor apart and cleaned it out. It turned over fine before, but wanted to be safe. i was glad I did take it apart, there were rocks in the crankcase that were seated while turning it slow, but would have made a mess had I fired it up. Just better to be safe than sorry and is also a good time to check out how the piston wear is.

Rocks inside the crank? wow, that's impressive. The best I've seen has been more of a muddy sludge. Does that engine run fine now? I'd be worried that the spray bar and fuel passages in the carb weren't damaged by the rocks on their way by.

Oh, btw, a scratch or two on the piston or liner isn't the end of the world. A friend of mine blew up the bearings in one of his .15's, the retaining cage let go, and it went though the engine and tore the heck out of everything, the scoring on the piston and liner were amazing. But he cleaned it out, put in new bearings and fired it up (after all, it couldn't hurt it any more than it already was), and it still ran quite well. Down a hair on power, but still plenty enough.

I went ahead and took of the backplate. Glad I did, found a little bit of dirt in there. Cleaned it out and got it back together. Fired it up last night and runs great! I am very grateful for all the advice given to me on this subject. Thank you all for the assist!

Luke