What happened here?

[oldbigred]

Well, I got a free Echo cs-510 the other day. Didnt get a lot of info on it other than the previous owner had run it and it started running poorly so he put a carb kit in it and it ran fine again. Then I guess it up and quit on him. So, I got it, and began checking it out and after muffler removal I found the exhaust side of the piston to be mangled rather oddly. Anyway, I went ahead and tore it on down to see if the cylinder was ok (more or less to see if it was worth putting a new piston in). The cylinder is really good for the most part except it feels a little rough below the exhaust port (as you would expect after seeing the piston). Anyway I think it should clean up ok as my fingernail didnt catch on any of the scoring but I tossed in a picture so you guys can input you two cents if desired. But my real question is what happened to that piston!?!? Check out the pic and let me know what you think...I dont want to put this thing back together if it just going to do that again. Also I should note the intake side of the piston is perfect...no scoring at all. Thanks for the help in advance.

 

[blsnelling]

Wow! Straight gas baby. Maybe a serious air leak. I'm surprised that jug will clean up.

 

[oldbigred]

You think so...the thing I dont get is why only exhaust side?

 

[GASoline71]

That's where all the heat is focused. Intake is slightly cooler due to the fuel charge comin' in...

That thing looks cooked mang...

Gary

 

[oldbigred]

Check the cyl pic...its a little blurry...but the thing really isnt very bad...hard to believe I know

 

[GASoline71]

You're right... it's blurry...

It doesn't look all that great to me... but try cleanin' 'er up and see whatcha get.

Gary

 

[oldbigred]

Maybe I'll see if I can bet a better pic...it looks worse there than it does in person.

 

[GASoline71]

The piston is shot... but if you can clean that cylinder up it might just be a go with a new piston kit.

Gary

 

[oldbigred]

Oh yeah...that piston's heading for the aluminum pile...she's smoked good

 

[oldbigred]

A couple better shots of the damage to the cyl. What do ya'll think...will it clean up?

 

[Grande Dog]

Looking at how much of the top of the piston on the exhaust edge is missing, I would think pre-detonation might have been your culprit. Usually with a lube issue the piston will still retain edge, and in some cases it will raise a burr on the exhaust side. It doesn't look like it actually deposited any of the piston on to the cylinder. You'll probably need to put a hone to it to find out.

 

[oldbigred]

Thats deffinitely a thought. The guy said something about someone else running ethanol in it...but that has higher octane around here so that shouldn't cause predetonation. But you are right there is a good portion of the top edge of the piston melted...and the ring almost appears to be melted as well...as far as the cyl I think I'll prolly take it down and talk to a local saw shop and get their opinion, but as far as I can tell it should clean up.

 

[poulson01]

Looking at how much of the top of the piston on the exhaust edge is missing, I would think pre-detonation might have been your culprit. Usually with a lube issue the piston will still retain edge, and in some cases it will raise a burr on the exhaust side. It doesn't look like it actually deposited any of the piston on to the cylinder. You'll probably need to put a hone to it to find out.

+1
Looks overheated. If straight gas had done it, you'd see the intake side washed out and scored.

 

[Jacob J.]

Make sure you get every bit of aluminum smear off that cylinder wall or your new replacement piston and rings won't last very long.

 

[teacherman]

Nice melt on the piston! I would do a search for muriatic acid cylinder cleanup, and follow the directions carefully. Looks like a lot of aluminum transfer to me.........

Hope you get it running again!

 

[oldbigred]

Thanks for the help guys. I've read a little on muriatic acid use...will have to revisit some old threads to make sure i know what i'm doing before i start. Also, seeking a bit more info...Grandedog thought it looked like predetonation could have been the cause, what are some common causes of this (where do I need to start looking to fix the problem)?? Thanks again.

 

[excess650]

Thanks for the help guys. I've read a little on muriatic acid use...will have to revisit some old threads to make sure i know what i'm doing before i start. Also, seeking a bit more info...Grandedog thought it looked like predetonation could have been the cause, what are some common causes of this (where do I need to start looking to fix the problem)?? Thanks again.

Detonation, or "pinging" is usually too low octane fuel, or advanced timing, or both. If there was significant carbon on the piston or in the combustion chamber, it would effectively raise the compression and require higher octane. Likewise, if those deposits got hot enough, you might get pre-ignition.

 

[oldbigred]

Well, I dont see that there is much in the way of carbon deposits anywhere on either the cylinder or the piston. So I suppose I should look at the ignition to make sure things check out there and if so I will have to assume low octane fuel was the culprit.