Piston Damage
 

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[:o]

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.........[sm=confused.gif] 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:eek:)

RE: Piston Damage
 

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!

RE: Piston Damage
 

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

RE: Piston Damage
 

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...

RE: Piston Damage
 

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

RE: Piston Damage
 

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.

RE: Piston Damage
 

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.

RE: Piston Damage
 

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.

RE: Piston Damage
 

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

RE: Piston Damage
 

look deeper, upstream,,, I'll bet your shedding ball bearing material, alot like tooth enamel decaying away

RE: Piston Damage
 

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.

RE: Piston Damage
 

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?

RE: Piston Damage
 

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...???

RE: Piston Damage
 

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

RE: Piston Damage
 

Any chance Bad Tooth of giving us a bottom view of the removed glow plug? From the photos you posted, I agree with the others on this thread in mentioning a serious Foreign Object Damage happened to your engine. In working in the engine maintenance field, I have seen this sort of internal damage before when spark plugs, and valve heads break during engine runs. Since you mentioned that the glow plug did not have an idle bar, I do not feel that the glow coil section could have caused that much deep metal damage. It is possible to clean up the cylinder head, but I would replace the rod, sleeve, piston and ring. The mention of a little rust on the bearings gives rise to just purchasing another engine as adding new bearings( why take a chance with the new parts)would make the repair cost in the ball park of a new engine. From a repair situation, it is not impossible to smooth out the pistion and cylinder head, and just replace the piston ring. How well the engine would run is an unknown.

Let us know what you decide to do, and how well the engine runs if you decide to repair it.

[email protected]
retired aircraft mechanic

RE: Piston Damage
 

I had the same thing happen to my GMS 1.20. After a close inspection, I found that the area of the piston where the wrist pin goes through came apart and got ingested. It wasn't pretty.

RE: Piston Damage
 

The engine is repairable, but at a cost.
ake it apart and check. You will probably find that some small metal particle has parted from where it belonged, probably a bearing cage as some posters before mentioned.
It's a good study object. Take it apart and learn, then prop it up as a paper weight to remind you of timely maintenance for your engines.

RE: Piston Damage
 

kinda like brushing your teeth, maintenace is big on these. I flew the 46FX alot, now I fly the AX, alot. First thing I noticed is the rear bearing does not last as long as they did on the 46FX. The front is original, they never wear out.

I keep an eye on my bearings and use a 16-18 dollar 'swiss' replacement with the plastic cage.

That prop better turn smooth as buttter before flight, otherwise it off to the engine hygenist.

Can someone smart tell me why the steel that's RIGHT next to bearing seems to want to rust first? like some kinda dis-simular metals ?

RE: Piston Damage
 

i see your talkng about a 50 , same deal for the most part, happy flying everyone !

RE: Piston Damage
 

I like the comparisons Splatter!:D I had really never heard about "bearing maintenance" before now. I always thought there was enough oil content in the fuel to take care of these little guys. Especially with O.S.; it almost seems to be a common theme with these engines. Rc-bearings.com lists a "most popular" bearings on their site and guess what engine takes the top 2 spots? OS 50SX-H for both.:eek:

Here are some more shots of the damage that was done: conrod nicked, rusted bearings, etc. The glow plug appears to just be missing the filament.

Anyone got an os 50sx or sx-h that they want to give up for parts.............?

RE: Piston Damage
 

As gross as the bearings look and the rod damage, if it's not the bearings it must be gremlins.[:@]

RE: Piston Damage
 

I have a 3W-106 that ingested something hard and it destroyed one cylinder and piston. It was a very expensive repair (new cyl/piston/ring, gaskets, etc.) and it was never determined what went through the engine. It left the other cylinder undamaged, and without any marks inside the crankcase.

Sometimes it remains a mystery...............

RE: Piston Damage
 

Bad Tooth,


Something ingested through the carburettor's fuel passage cannot do such damage (since it is too small).

It is either something metallic that was pulled in through the carburettor's air intake (or a part of the carburettor - anything missing?), or more likely, a piece of the rear bearing's cage.



Your engine's rear bearing seems very corroded, but is the cage in one piece?

Sometimes just one individual 'shell' parts company with the rest of the cage and 'takes a trip through the engine', or from your photo of the front bearing, perhaps a rivet holding both sides of the cage together, 'let go' and took the same trip...

Closely examine the rear bearing cage, using a strong light and a magnifier.
See if all the balls are surrounded by a cage-shell on both sides and if all the rivets (or tabs) holding the cage together are in place.

Balls and their shells look very similar, so look closely.


The OS.50SX has been noted, by other people, as likely to consume its bearings.

RE: Piston Damage
 

I think if you have damage in the conrod and in the cranckase it must have been an Foreign object that come through the carb or come loos from the bearings...and the particle followed the gasses stream. I think a particle generated inside the comustion chamber would rather go through the exhaust port than through the admission ports. So the engine must have ingested it...

Have you checked the carb for missing parts?

RE: Piston Damage
 

Dar is absolutely right.

What about the round shape dent that the conrod end has?? it was like it pressed something ball shaped or something!