Stihl fs490

[laustin956]

Hi got a stihl fs490 the clutch has suized over the last few months rev it no head spin the it did move but at low revs it cuts out took it apart and a bit rusty. What the best way to clean it and do you need to grease it

Edited January 24, 2016 by laustin956

[adw]

The clutch on a brush cutter cannot seize, the clutch will be connected to the crankshaft, there will then be a bell housing with a drum in that sits over the clutch, the drum will be connected to a shaft which runs down the inside of the tube, the other end will fit into a gearbox which then turns the head, so which part has seized, take the gearbox off, does the shaft turn with the engine at full revs, if yes the gearbox has an issue, if it does not turn the shaft may have seized in the tube, many tubes have oilite bearings so do not need grease, some have nylon liners which do need grease, the gearbox also needs grease.

[laustin956]

Hi the 3 part of the clutch don't move only if i force them with a screwdriver to open the up the engine runs fine

[adw]

The clutch is centrifugal, so the shoes only come out as the engine revs, there are strong springs that hold the shoes in because you do not want the shoes coming out at idle, so as long as you can open them with a tool i would say its ok.

[Benny4817]

The clutch is centrifugal, so the shoes only come out as the engine revs, there are strong springs that hold the shoes in because you do not want the shoes coming out at idle, so as long as you can open them with a tool i would say its ok.

just beat me to that comment then lol check each item in line that it actually moves and grease where needed gearbox etc

[WoodED]

Does the engine rev or sound like its jammed? Check the cutter head is on correctly, if bits are missing it can lock up,

If none of mine or the other sujestions bring you anyluck then take it to your dealer

[Benny4817]

may even be just as simple as some foreign object string plastic grass rope binder tape etc stuck between head and gearbox ,, was it working fine then just stopped have you have head off and any chance you have not put all plates covers back etc if so the space will be reduced and head will catch

[laustin956]

Like i say if I use a screwdriver and pull the clutch shoes out they say out and will not pull in

[Haironyourchest]

my bet is that the culprit is that plate that is held on with three bolts in the photo. There is more than likely a mirror plate on the other side of the clutch shoes. The shoes must be able to move between these two plates in order for the centrifugal action to fling them out far enough to contact the clutch drum.

 

The clearance between the shoe, sandwiched between these plates, is pretty tight. If rust or gunk has built up, it could be causing the shoes to stick.

[GardenKit]

Stihl brushcutter clutches do seize easily, I see a lot of them.

I must admit to not having seen a 3 shoed clutch, but the 2 shoed ones seize regularly.

The shoes are sandwiched between 2 plates and a little rain on a hot clutch causes the shoes to rust and stick between the plates.

The shoes also have a pivot bush which easily rusts.

This sticks the shoes hard enough for centrifugal force be insufficient to move the shoes out.

Dissmantle, cleqn, lubricate and reassemble.

 

There are some images of the two shoe version on post 14 of this thread

http://arbtalk.co.uk/forum/maintenance-help/95574-sthill-fs450-vibration-2.html