stihl FS 74

[Shady Brook]

Anyone have any thoughts why an FS 74 will run, sort of on nearly full choke, but will die quickly if I let the choke out? She is smoking a great deal, in the viscinity of the muffler, and also around the head. Anyone know what minimum compression should be on this unit? I have changed out the carb, and exactly the same symptoms. Gas is not an issue, I am thinking it is bigger and more expensive things. Does this sound like the engine is on it's way out. Tons of black crud buildup in the exhaust area leading to the muffler.

Any thoughts are greatly welcome.

Thanks
Jay

[P&J Lawncare]

did you pull the screen out of your muffler if not it can build up with carbon fast.

[Shady Brook]

screen is not an issue
Jay

[Fish]

Remove the muffler and look at the piston and
describe what you see.
Fish

[Shady Brook]

Couple small abrasions on the piston's side. Piston does not receed all the way below exhaust port opening. Not sure what else to say.

Jay

[Fish]

Any piston scoring is bad, and the future for your
trimmer is bleak. Hate to say it, but your money would
be best spent buying a new one. If you buy the same
model, at least you will have one for parts. If you want
a different brand, look at Shindaiwa or Echo. Putting
in a new piston and/or cylinder would approach the
cost of a new one, and then still you would need to
find out what damaged the piston to begin with.
Fish

[khouse]

Fish is right. Sometimes you just have to get a new unit....