Used engine inspection
 

Just received my first used engine in the mail today. I have always been a little leary, but figured I would give it a shot and see what happens. I purchased an OS 55AX for $99 shipped. As per the ad, engine was like mint condition, slightly used with only about 8 flights ( give or take 20 im sure). Anyhow, first thing I did was take the engine apart. It appears to be in very good shape. Everyhting is nice and smooth. For you engine experts, Im sure its normal, but was wondering what/ if anything the piston would be able to tell you about the initial runs? SEE PIC.
If there is anything specific we should be looking for when inspecting a used engine, please fill us in.

Im gonna try and make sure to run the engine this weekend. Compression is strong. Wondering if I should run it per the manual as if I was breaking it in, or is it too late for all that and just run it normal?

RE: Used engine inspection
 

Hard to tell from just a pic but it appears OK. Some staining on top of the piston is normal. The main things I look for are obvious physically broken external parts, bearing condition, excessive or abnormal rust, excessive piston/cylinder scuffing, metal transfer between parts, slop in rod bushings, etc.

Truth is, if it felt good, you probably didn't even have to take it apart. Taking stuff apart is fun though so I probably would have done it too.

RE: Used engine inspection
 

I would avoid disturbing the piston cylinder fit on any engine that has run if I can avoid it.

Take off the carb prop driver and backplate by all means. This lets you see if the crankshaft is scored at the inlet port and allows a visual inspection of the bearings and big end. I personally do not go further than this unless I have to.

RE: Used engine inspection
 

I am from the old school and IMO running an engine on a test bench is ok! Put a little time on it and get the needles within ballpark adjustment...thats it! Final break-in and tune done at the field and in the air ;)

RE: Used engine inspection
 

The top of the piston looks like the seller told you the truth. I just look at the piston through the ports for any scoring and roll the engine over by hand to feel the bearings for any rough feeling or binding then do what duncker does, pull the back plate and look for any rust. Then I just fire it up. If it's a very old engine I do strip them down all the way and clean them if needed.

RE: Used engine inspection
 

If the engine can hold a seal for a good long time after bringing the piston up to TDC, that's a very good sign. After dousing / lubing, etc., the prop should "toggle" freely after flipping through compression. It's a good idea to rotate the engine and try to feel for anything that isn't velvet smooth going on.
Pulling the head and backplate is OK to be done routinely, but the piston / liner shouldn't be disturbed...there's nothing to be gained unless there is a known problem that needs to be remedied.

RE: Used engine inspection
 

I don't usually bother taking anything apart. If it feels good, I put it on a plane and run it. If it runs reliably on the ground, then I fly it. The only reason to take it apart is if you're either planning on replacing the bearings anyway, or you think the seller lied to you and you're planning on sending it back for a refund. For my money, taking an engine apart just introduces opportunities to screw something else up.

I've only ever purchased two new engines. An LA 46 I bought 6 years ago, and a DLE-55 in August. Everything in between was either E-Bay or RCU Auction. The list includes two TT Pro-46's, an OS-46 FX, a TT GP-61. and two Magnum 91 FSRs. Not a bad running engine in the lot.

Brad

RE: Used engine inspection
 

Well, there's a first for everything - and this was my first used engine. I took it apart for piece of mind. I'm happy with what Ive found. The engine looks to be in excellent condition so far. Ill be running it this weekend and expect it to do well. I post a lot of questions on rcu - thanks for the responses. They've saved me time, money and have learned a lot in the last 3 years from the experience of others.