That sounds like mine did. I put a new plug, cleaned the oil and grass offof it, dumped the old gas and mixed up new fuel using high test gas and now it runs perfect.
I'm pretty sure that there is a problem with the carb., with it being a FS-86 it should be old enough to still have adjustments on the carb. if so I'd start by turning the low (L) side needle out (counter clockwise) about 1/8 turn and see if that helps. If the carb. has no adjustment or only hi (H) then I would change the metering diaphragm on the metering side of carb.. As far as a timing issue it's not, unless there is a problem with the flywheel. on a 2-cycle string trimmer the timing is set were they have the flywheel keyed to the shaft and is non adjustable.
Answers & Comments
That sounds like mine did. I put a new plug, cleaned the oil and grass offof it, dumped the old gas and mixed up new fuel using high test gas and now it runs perfect.
I'm pretty sure that there is a problem with the carb., with it being a FS-86 it should be old enough to still have adjustments on the carb. if so I'd start by turning the low (L) side needle out (counter clockwise) about 1/8 turn and see if that helps. If the carb. has no adjustment or only hi (H) then I would change the metering diaphragm on the metering side of carb.. As far as a timing issue it's not, unless there is a problem with the flywheel. on a 2-cycle string trimmer the timing is set were they have the flywheel keyed to the shaft and is non adjustable.