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Piston Damage - 4/5/2008 12:44:03 AM   
Bad Tooth



Posts: 195
Joined: 5/6/2003
From: Lawton, OK, USA
Status: offline 		Ok guys, on my second flight today my O.S. 50sx sputtered and died. I found out that I had enough fuel so I checked the plug and it was gone. So I replaced the plug and tried to start it up again and noticed it was making a horrible clanking sound. It also seemed to have much less compression than normal. I was using an electric starter so it turned over a few times

I got it home and took it apart and this is what I found. I thought at first it was the element from the glow plug, but I don't think that could do that much damage could it? What could have caused all this? I took the whole thing apart and never found the culprit......... The piston sleeve and everything else seems to be ok. The connecting rod also has a couple of nicks in the outside of the ring.

Can I just replace the piston, head, and ring?


(and no, I don't have a fuel filter on this plane )

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       Post #: 1

RE: Piston Damage - 4/5/2008 12:48:27 AM   
Spetz


 

Posts: 1354
Joined: 9/7/2007
From: , CYPRUS
Status: offline 		You'd have to replace the piston, maybe not the head? And if the sleeve is bad you'd need to replace that

This would be caused by running too lean and getting detonation I'd say

Looks nasty!

(in reply to Bad Tooth)
       Post #: 2

RE: Piston Damage - 4/5/2008 12:55:54 AM   
somegeek



Posts: 2084
Joined: 8/1/2005
From: Vancouver, WA, USA
Status: offline 		How does detonation cause that damage?

Looks like you had a metal chunk dance it's way around your head. Did you find any metal chunks in your crankcase? How do the bearings look?

I had similar damage due to combination of a rusty rear bearing and some momentary high RPMs(recent post here in the glow forums w/ pics). Not fun.

somegeek

< Message edited by somegeek -- 4/5/2008 12:59:47 AM >

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RE: Piston Damage - 4/5/2008 12:55:55 AM   
Broken Wings



Posts: 491
Joined: 1/15/2003
From: Spaceport, FL, USA
Status: offline 		What knd of glow plug was it? It looks like something real hard got loose "like the idle bar"...or it ingested something (bearing parts). Is the ring free in the ring groove? It looks like it took a pretty good shot in picture two. Find a lathe and you "may" be able to clean it up. Otherwise it looks like a new piston/ring.

Bummer...

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       Post #: 4

RE: Piston Damage - 4/5/2008 1:01:50 AM   
aussiesteve


 

Posts: 1072
Joined: 10/12/2005
From: TEDA (Tianjin)Tianjin, CHINA
Status: offline 		Looks like foreign object damage to me and at a guess, I'd say it was caused by something much larger than anything that would have come throught the fuel system.

When you say the glowplug was "gone" do you mean it had come out of the head or had the filament disintgrated? What sort of plug was it? did it have an idle bar?
Is it possible that something has entered the cylinder from the bottom end? such as parts of a disintgrated bearing?

As Spetz said - if there is any damage to the liner -replace it too

The sharp edges on the damage to the head would need to be polished out otherwise you will probably get hot spots on them and possible detonation. If it was mine, I would replace the head. Are the glowplug threads stripped or is it just the way the photo shows?

Consider the price of all the spares you will need and compare that against a replacement engine such as the Magnum 52XLS

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       Post #: 5

RE: Piston Damage - 4/5/2008 1:05:13 AM   
mandtra


 

Posts: 134
Joined: 4/21/2005
From: clermont, GA, USA
Status: offline 		I would say Lean run . I have seen similar , but that is the very worst I have seen. . I would scrap the engine. Time you buy a piston, ring , head , head shim your around 80$ not to mention bearings, which I would replace If I was going to repair. and I junk it and use for parts.

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       Post #: 6

RE: Piston Damage - 4/5/2008 1:20:53 AM   
XJet


 

Posts: 3462
Joined: 3/31/2003
From: Tokoroa, NEW ZEALAND
Status: offline 		That's not detonation damage -- detonation produces much more radiused pits. That was definitely caused by a foreign body that has made its way into the cylinder.

I'm picking it's a bit of the bearing cage (yet again).

Strip the engine and I think you'll find that the cage on the rear bearing has started to disintegrate.

That's why *I* don't use metal-caged bearings any more.

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       Post #: 7

RE: Piston Damage - 4/5/2008 1:27:09 AM   
Bad Tooth



Posts: 195
Joined: 5/6/2003
From: Lawton, OK, USA
Status: offline 		I don't know what kind of plug it was but it didn't have an idle bar. The threads in the head appear to be ok. I was actually coming over the runway when the engine started to sputter, so thinking I was getting low on fuel I turned around and the engine died. So it was running for I'd guess 15 seconds from first sputter to when it quit.

The bearings appear to be in good shape, a little rust but that's all. Once I removed the piston/sleeve, the crankshaft felt pretty smooth before I removed it.

Do you really think just running lean could cause this? I'm pretty sure it was running fairly rich. It looks to me like it swallowed a steel bug!

Piston/ring and new head = $80.

(in reply to mandtra)
       Post #: 8

RE: Piston Damage - 4/5/2008 1:38:11 AM   
YUKONFLYR



Posts: 256
Joined: 4/18/2007
From: WHITEHORSE, YT, CANADA
Status: offline 		Looks to me like its been stamped if not internal FOD maybe external FOD. Definatly not detonation damage.

In my work we seen large 15 litre heavy duty engines swallow all four tulip valves, crunch them up and spit it out thru the turbo. Chances are that you may never know what the object was that did the stamping of the piston and head if it was not internal, as it probably left via the exhaust

Bad Tooth, did you have a look at the small end of the rod? I had a piece come off the small end once and stick the piston to the top of the head.

Richard

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       Post #: 9

RE: Piston Damage - 4/5/2008 2:50:11 AM   
Super Splatter



Posts: 395
Joined: 3/21/2006
From: , MN, USA
Status: offline 		look deeper, upstream,,, I'll bet your shedding ball bearing material, alot like tooth enamel decaying away

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       Post #: 10

RE: Piston Damage - 4/5/2008 2:51:44 AM   
delman


 

Posts: 479
Joined: 4/29/2003
From: Flower Mound, TX, USA
Status: offline 		I have a 50sx that did that. A small piece of the ball bearing retainer had come loose in the engine. I had to replace the rear bearing, piston and ring and dress out a small burr at the exhaust port where the piece left the engine. It has been running good since.

(in reply to Bad Tooth)
       Post #: 11

RE: Piston Damage - 4/5/2008 3:04:06 AM   
Bad Tooth



Posts: 195
Joined: 5/6/2003
From: Lawton, OK, USA
Status: offline 		I just got done reading SomeGeek's experience with his .46ax. Although I haven't taken my bearings out they don't look much better than his bad bearing. The rear bearing also seems to have a little slop in it. Today was a really windy day and going downwind it was really winding up. Probably too much eh?

(in reply to delman)
       Post #: 12

RE: Piston Damage - 4/5/2008 4:04:34 AM   
proptop



Posts: 4508
Joined: 10/18/2002
From: Rome, NY, USA
Status: offline 		You'll probably need to remove the rear bearing to get a real good look at the ball retainer...
Looks to me (as well ) like part of the bearing retainer...could be the folded over tab(s ) are breaking off?

If it already has a plastic caged bearing, then...???

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       Post #: 13

RE: Piston Damage - 4/5/2008 5:57:00 AM   
rcdude7


 

Posts: 1018
Joined: 4/12/2003
From: Maryland
Status: offline 		Time to replace that engine. I would bet my paycheck that the sleeve is damaged also. OS is very proud of their engines, and the price of spares reflects that thinking.
The only other cost effective option would be to get a crashed OS .50 cheap and strip the parts needed to get this engine running again.
I did this to get a MOKI 1.35 running again after it ingested a wrist pin retaining clip and sustained severe piston/sleeve damage. I bought up a crashed MOKI 1.35 for $40 and combined the good parts I had to get a excellent engine. I got lucky. The price of new parts would have been around $200, give or take a few.................

Post a ad in the RCU engine wanted section and wait. Maybe you'll get lucky.

Mike

(in reply to Bad Tooth)
       Post #: 14

RE: Piston Damage - 4/5/2008 7:46:00 AM