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New here - 346XP with a ground electrode that broke off in the cylinder

Underwhere

Underwhere

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Was bucking some logs yesterday when I felt the chainsaw bog a little bit. At least I thought I did. I wasn't sure.

Suddenly I hear "clacking" coming from the saw and I immediately shut it down.
My first thought was that it had overheated and was detonating so I let it cool off for a few minutes and tried to restart it.
I gave the pull cord a tug and it was locked up.

So I started to disassemble it and noticed the spark plug was fairly loose in the cylinder. Then I noticed the ground electrode was missing.
I have a cute little scope camera and took some shots of the piston head and the cylinder walls. The head looks like it was nicked up a bit but the walls don't look too bad.

Any advice on what to do next?
I was thinking of just tossing a new plug in and running it.

Then the idea of buying a new piston and cylinder came to mind...maybe modifying it for fun. Never done that before.

I bought mine used back in 2013.
I'm assuming it is the 50cc NE version because it has a silver clutch cover but no green fuel cap.

Any guidance would be appreciated here.
 
buzz sawyer

buzz sawyer

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Are you sure the plug is correct for the engine? Maybe contact the spark plug mfg? Defective plug? Have you pulled the muffler to look for other scoring? I'd be concerned that something might have gotten on top of the upper ring and is waiting to score. I think I'd at least pull the jug to check.
 
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John Lyngdal

John Lyngdal

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I'd pull the jug as well, especially if you can't find the electrode metal, as it could be in the muffler or crankcase.
The piston looks like it needs to be replaced. I'd lightly clean the cylinder bore with oil and 600 grit just to see if there is more damage than the pictures show.
Please post more pictures of the spark plug as it would be nice to know the manufacturer and part number.
 
Underwhere

Underwhere

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Ok thanks for the advice.
I'm mechanically capable just never concentrated on chainsaws. By "jug" do you mean the cylinder head? I gotta figure out how to get it apart. Shouldn't be too hard.
 
Underwhere

Underwhere

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Out of curiosity if I pull the "jug" would this be the time to do some dremel work?
I saw some videos of someone grinding down the bottom of it.
 
Underwhere

Underwhere

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That spark plug is missing the compression/sealing washer. With that gone it will stick down into the cylinder too far and the ground electrode may contact the piston. Time for a full tear down and inspection. AKA... hunt for that missing piece.
I think that's just a bad picture. I remember pulling the washer out with it.

I will find that missing piece. Will be fun.
 
Tobystihl

Tobystihl

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I've had two 550xp's in for repair with this same problem, I believe the plugs were Bosch. In Both cases the pistons were fubar but the cylinders were Ok.
My fingers are firmly crossed for you, Good luck!
 
Underwhere

Underwhere

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OK so I finally found my tools (away in boxes at the moment).

Here is the piston head, then cleaned up with 800 grit.

And here is the cylinder.
The walls seem totally unscathed though there is a cylindrical dent in a port. It's not rough though.

The top of the cylinder seems a bit nicked but not too bad... I guess that is relative and I don't know what to compare it to.

 
Underwhere

Underwhere

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Some questions:
1. Would you replace the piston and the cylinder? Just the piston?

I have a few more questions and I thank you guys for your patience. Again I'm not a chainsaw guy so I am struggling through some terminology and some some modifications.
I bought this saw used from a guy who seemed to make a business of restoring saws. I'm assuming he himself already made some changes.

1. My cylinder had no gasket. Can I assume he did this to increase compression? He used some orange sealant.
2. My muffler has no cat and had no screen. Is the MM just to cut some holes in it and weld on short piping so the exhaust can breathe a bit better?
3. I see the exhaust port has a carbon deposit outline. Should I grind away and open up the port to match this outline?
 
grizz55chev

grizz55chev

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OK so I finally found my tools (away in boxes at the moment).

Here is the piston head, then cleaned up with 800 grit.

And here is the cylinder.
The walls seem totally unscathed though there is a cylindrical dent in a port. It's not rough though.

The top of the cylinder seems a bit nicked but not too bad... I guess that is relative and I don't know what to compare it to.

seen worse!
 
Underwhere

Underwhere

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grizz55chev

grizz55chev

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On the other hand an aftermarket cylinder and piston is apparently only $30
Just say no to the aftermarket cyl., yours is still good! Many manufactures use the Meteor brand piston and like i said earlier, its a bargain at around $40.
 
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