Stihl fs90 spinning on idle

[shiggins]

Hi, im new to the group.
My fs 90 wasn't idling. Woudl start well and then stall when letting it idle. Haven't used it in a couple of years. Used new fuel etc.

I went to check what the L and H screws were set too so screwed them in seated and then back to position. Both 3/4 turn, however It didn't matter as they are fully open to the restrictor caps anyway.
I screwed the idle in a bit and gave it a bit of carby cleaner.

It's running now but when I back the idle off it keeps spinning and eventually stalls while spinning. If I hold the spindle at the cutting end it stalls straight away. The clutch spring is ok although looks a bit rusty.

Any help ?

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[Turd Ferguson]

I'd try a new carb - especially if it hasn't run in awhile. Aftermarket carbs are cheap enough and pretty straight forward to replace. While you are at it new fuel lines and filter wouldn't hurt.

 

[Canadian farm boy]

I’m not familiar with this model but it sure looks like 1 of the clutch shoes is stuck. If the clutch is slightly engaged it will drive the spindle even at idle and can cause the stalling at idle speed and your idle tuning issues.

 

[shiggins]

I'd try a new carb - especially if it hasn't run in awhile. Aftermarket carbs are cheap enough and pretty straight forward to replace. While you are at it new fuel lines and filter wouldn't hurt.

The primer was broken so it's a good shout. The carb could have some *s-word in it.

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[shiggins]

I’m not familiar with this model but it sure looks like 1 of the clutch shoes is stuck. If the clutch is slightly engaged it will drive the spindle even at idle and can cause the stalling at idle speed and your idle tuning issues.

The top one ? Good point. I'll get it off and have a look.

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[Filthyphil]

Im having the same problem with mine. The clutch was sticking. The drum and clutch was all rusty. I cleaned everything up and tried again its good till i hit the throttle then it get stuck again. It seems simple and should be easy to figure out but i cant seem to fix it. Gonna end just buying a new clutch.


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[shiggins]

Im having the same problem with mine. The clutch was sticking. The drum and clutch was all rusty. I cleaned everything up and tried again its good till i hit the throttle then it get stuck again. It seems simple and should be easy to figure out but i cant seem to fix it. Gonna end just buying a new clutch.


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I think they are pretty cheap hey.

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[Filthyphil]

I think they are pretty cheap hey.

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I wanna say the full setup was like $80. More then i wanted to spend. I just got three more in a parts lot i bought. Gonna try to make one good clutch from those three machines but im not gonna hold my breath.


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[JB-PlantHeirloom]

Did you solve it? From my experience it is almost always the springs are bad. BUT, I had one where the pivot was bad. If the spring is weak, it will drag on the drum and make it hard to start or kill the engine because the engine is not hitting it's peak torque before the clutch engages.

On a Ryobi it had the same type problem, BUT, the cable inside the tube was wrecked and it would stall the motor when engaged and made it hard to start because it would not freely spin.

 

[Onan18]

I have tried cleaning up rusty clutches that stick time and time again, always end up replacing them after wasting an hour or better trying to save them.