Echo CS-590 wont idle, scoring on new piston. Air Leak?

[freebilly]

I would like to comment on the piston scoring due to high end lean condition. The OEM carb on cs-590 has an extra fuel "nozzle" on the high circuit. It has been well documented on this site. I believe it is difficult to lean these saws on the high end. IF, the carb is in working order...

That is correct, another reason I am confident it wasn’t running lean on the high side.

 

[ZeroJunk]

That is correct, another reason I am confident it wasn’t running lean on the high side.

Well, WTF was it ? You run out of stuff. I suspect you were off on the cylinder on your original rebuild.

Or, whatever. They do not gall for no reason.

 

[stihltech]

Never say never. That is how you get a scored cylinder. If it is truly air and vacuum tight, you have a lean condition. The WHOLE fuel system is still suspect.
Too many years in a shop I guess.

 

[stihltech]

That extra jet to let the fuel in around the high speed jet must not be plugged or you will get you have now as the end result.

 

[telecasterfool]

That extra jet to let the fuel in around the high speed jet must not be plugged or you will get you have now as the end result.

I have a 590 with the 620P carb. I have removed the plug that has the extra "nozzle" for the high circuit, and replace it with the carb manufacturer's plug that does not have a nozzle. This has been well documented already on this site. If someone wants the part number for the replacement plug, I could dig it up. This modification removes any extra fuel on the high circuit, and makes the carb run like any other old school carb. Saw runs fine, I'm just sure to keep it rich on the high end, and tune it for the seasons like any other saw. Please ask any clarification questions you like. I'm not picking a fight - information exchange is what I'm here for.