my english might be bad, but i try my best...
pictures needed. ive seen this problem here in EU. 550xp is a very good saw when u are a "home hobby technician" (pro loggers here are just dumb*sses and wont care about their tools)
in times there were some updates to that saw line (545/550xp) and what might be the case here.
common problems here so far are:
*piston ring pin/stopper loose in piston after few (to 100) hours on it. result: wrecked Cylinder & Piston.
*crankcase gasket leakage. result: scored Piston & Cylinder
*cylinder gasket leakage(tightening bolts regurally is needed, by the client/owner also). result: scored Piston & Cylinder
*cylinder transfer covers and seals leakage. result: scored Piston & Cylinder.
*crankshaft or bearing failure, crank spins in bearing(no matter what side). result: bad vacum/pressure in crankcase. result: saw wont start, work properly when engine cold or warm. some had scored cylinder piston aswell.
*crankshaft lower needle bearing breaking, big tolerances. result: basically worst what u can imagine, seen also splitted rods. everything is possible
*crankshaft bearing breaking both sides. result: engine is permanently stopped. have seen also working ones, but these were only making some kind of dying noise.
*carb failures(maybe due a bad patch of fuel, maybe bad part from the carburettor supplier...). result: saw wont idle, rev up, or even start.
*heavy abuse of the saw, dull chain and large wood, very dirty chainsaw, low cooling effect, overheating - the engine/ECU do not now what to do. result: piston ring burns in piston groove due carbon
*have seen also a non quality JASO FB fuel mixig oil fail, due the lubrication and overheating - the engine/ECU also wont know what to do. result: piston ring burns in piston groove due carbon.
*have also seen after 150 hours, the worn out oil seals on both side of the crankcase. Result: saw wont idle, rew up, and some times scored piston & cylinder.
and yes im still a Husqvarna fanboy (still have the legendary old ones for me, to keep)
