Tried DIY, but no replies to date. Sthil FS38 bent shaft line trimmer. Stopped while in use as though it had been switched off. Has spark, but replaced plug & CD unit anyway, cos I had one here. Stripped carb. Can't see anything wrong. Ex system off, & not blocked. None of this made any difference. When pulling start cord, fires occasionally out of the carb. Just one pop. Nothing else. Ever. Starting to think crankcase seal. Any other ideas before I ring the Echo agents for a replacement! TIA. PS - 100ks over water from the nearest agent.
intrade,
Apr 10, 12:11am
i tell you what is wrong. The flywheel has shered off the key and is now in the wrong position for the spark. hence it fires out the carb. You got to pull it off and repair the key. Well that is what it sounds like from your discription above.
richard112,
Apr 10, 12:19am
Hey, intrade. Thank you. Been thinking it sounds like the timing was out, but that's impossible. OK, It's not. I'll get back out & have a look at that.
whqqsh,
Apr 10, 12:44am
some just have a plastic 'key' moulded as part of a plastic flywheel, shear off easily
richard112,
Apr 10, 1:17am
Thought we must have had it. Can't actually see the keyways, but the magnets in the flywheel appear to arrive at the CD unit just before tdc, so I think it's probably not that. Would probably need special tools to get at it without butchering as there is a centrifugal clutch on the shaft immediately in front of the flywheel. Flywheel is alloy. Thanks all.
alfred011,
Apr 11, 5:40am
the simple way to get off flywheel nuts and clutches is remove sparkplug and feed in rope to lock piston then you dont get any damage.
jmma,
Apr 11, 5:44am
Seized it, No oil in the petrol.
supernova2,
Apr 11, 5:56am
Stuffed reed valve!
jmma,
Apr 11, 6:12am
Don't have one (o:
skin1235,
Apr 11, 5:13pm
then think again, it will be the keyway it doesn't have to be completely shorn off to stop the engine - briggs and stratton mowers do the same ( especially if you find a brick hidden in the lawn lol) and aften they have merely squeezed the keyway, the flywheel has only moved a 1/2mm on the shaft and not completely shorn the keyway off also if you think about it, the magnets should be well past the tdc point when the piston gets to tdc, they produce the current to load the capacitors that give the spark, if they're only just getting there the capacitors will not be charged, you will however get a spark later in the cycle once they have charged - thats the single pop out of the carb occasionally
skin1235,
Apr 11, 5:17pm
as someone else has said, remove the plug, feed thin rope down the hole until you can feed no more, this locks the engine while you remove the clutch, - some are left handed threads so use caution, the clutch id also the flywheel nut, once it is off you can often tap the flywheel and it will come off, some have to be pulled off, be careful if you are trying to prise it off, the engine case is not very thick and will crack if you're leaning on the wrong bit
skin1235,
Apr 11, 6:40pm
#10 assumes cdi ignition, if it is simple coil type the spark occurs at breakdown/reversal of current, ie as the second magnet enters the coil poles what you describe is typical of keyway blown, the spark will be severely retarded
alfred011,
Apr 12, 5:27am
That stilh is probably just a ryobi in orange and white plastic.
richard112,
Apr 12, 4:40pm
Been away for a day. Thanks all. Very very meticulous about Oil. 50:1 stihl oil since new. No reed valve. Hadn't heard of the rope trick before. Excellent. Problem is that the centrifugal clutch is on the shaft hard up against the flywheel, and couldn't see how to get that off without butchering it. Snoopy below from DIY may have answered that. I've looked for a fastener & couldn't see anything, so it must be bloody small. Unfortunately, already ordered a new machine, but I'll go back & try one more time out of principle.
Snoopy "End of the day it will be a flywheel key by the sound of it. Where the shaft goes in to the end of the clutch there is usually a small no2 torx screw-however you need a long torx tool to undo. Undo that and the outer of the clutch comes off. Then the clutch plates are threaded and unscrew-the plates are effectivley the flywheel nut".
cowlover,
Apr 13, 8:57am
How can a2 stroke work without a reed valve!
richard112,
Apr 13, 2:25pm
If there is no reed valve, you'll find they have a longer than usual inlet manifold. Some even swan neck shape. (Very stubby swan neck) so I guess it's a pulse thing. I guess. Back to 15 above. Had a look. Snoopy was right, but the tools I have are too fat to fit down the hole to the screw. Will have to grind one down. Sadly out of time now, and the new machine & long grass are calling. Thanks all once again. I've learned a hell of a lot here.
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