550xp mk2 dies at full throttle under load

[Wood Doctor]

Looks like it was vapor lock and/or heat. I let it cool down and then it fired right up several times in a row with the warm start technique. Like many Stihl saws I have worked with. the fast idle setting is a must on start up. I am a bit surprised that the manual says to prime it with the purge bulb several times even when warm. Anyway, it's a go and thanks Guys.

 

[treemuel]

Revisiting this post because the saw started acting up again with the same issue! It has run perfectly since taking apart the carb and cleaning the screen (about a month of consistent use). I also swapped the fuel filter for a blue top one. Then yesterday all of a sudden it started doing the same thing as before–dying at full throttle, particularly when I flip the saw on its side. Seems strange that the carb could have gotten clogged up so soon... Or maybe that wasn't the underlying issue but something else I did in the process of rebuilding it temporarily fixed whatever it was? Any ideas out there? Figure I'll just pull the carb apart again, but I'd love to get to the bottom of this and not keep dealing with it.

 

[Motorka]

Had this problem on h 55. Dissemble carb and put him in ultrasonic cleaner.

 

[Wood Doctor]

I would next do a compression test or inspect the piston. You could be needing a new top end rebuild. That was what killed the 550 XP that I worked on. The ring was flat against the piston on the intake side.

 

[big_eddy]

If it’s happening when you flip the saw on it’s side, time for a pressure/vac test. Could be a crank seal going.