# Stihl trimmer problems (long post warning)



## Knuckles (Aug 31, 2009)

I hope you guys can help me. My father brought over his Stihl FS 80 trimmer (cira: 1995) this afternoon with complaints that it stalls when the engine gets hot. Says it starves for gas when you squeeze the trigger.

This thing has a "California" carb on it. As in, it doesn't have any external adjustments other then a idle screw. I've never seen anything like this before. It's kind of a pain since it runs lean as hell. But you can't do anything about it.

I haven't had any time to really check it out yet. What should I look for? I've rebuilt carbs before, but those wouldn't even start without acting stupid. This trimmer will fire and run for a few minutes before it dies. 

What is getting hot that's causing it to act up?


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## joatmon (Aug 31, 2009)

I had one that acted just as you described. Many frustrations, a twice stumped dealer and still no resolution.

Tom Hall said replace the card. Did it. Runs perfect. Here's the thread I initiated: http://www.arboristsite.com/showthread.php?t=97362&highlight=fs80

Good luck,


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## 2000ssm6 (Aug 31, 2009)

joatmon said:


> I had one that acted just as you described. Many frustrations, a twice stumped dealer and still no resolution.
> 
> *Tom Hall said replace the carb. Did it. Runs perfect.* There's a thread here I initiated: http://www.arboristsite.com/showthread.php?t=97362&highlight=fs80
> 
> Good luck,



That and there was something about the plastic intake block cracking and expanding when hot, could have been on the fs85 though....


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## Rookie1 (Aug 31, 2009)

Id go through the fuel system. Check fuel lines and filter. Then I would rebuild carb or at least take it apart and clean it. If its that old I wouldnt be surprised if it had junk in it.Also if its ran this long with a no adjustment carb it must be set pretty good from the factory to have not leaned out and scored the piston all these years.


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## Scooterbum (Aug 31, 2009)

+1 carb for that is cheap.
Might check your exhaust screen while your at it.


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## joatmon (Aug 31, 2009)

2000ssm6 said:


> That and there was something about the plastic intake block cracking and expanding when hot, could have been on the fs85 though....



Brian,

That's what the dumba$$ dealer told me. He had me fooled, for a while. I ordered that part and it didn't do the job. ole Tommie set me straight. That thing runs good now.


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## 2000ssm6 (Aug 31, 2009)

joatmon said:


> Brian,
> 
> That's what the dumba$$ dealer told me. He had me fooled, for a while. I ordered that part and it didn't do the job. ole Tommie set me straight. That thing runs good now.



Let's act like I didn't even mention that detail, LOLOLOL.


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## THALL10326 (Aug 31, 2009)

Knuckles said:


> I hope you guys can help me. My father brought over his Stihl FS 80 trimmer (cira: 1995) this afternoon with complaints that it *stalls when the engine gets hot*. Says it starves for gas when you squeeze the trigger.
> 
> This thing has a "California" carb on it. As in, it doesn't have any external adjustments other then a idle screw. I've never seen anything like this before. It's kind of a pain since it runs lean as hell. But you can't do anything about it.
> 
> ...



Could be a coil, could be a carb. That stalling when hot comment needs to be described in a little more detail. A bad carb causes problems from start up, not just after it warms up. So, is this unit starving for fuel from start up or only after it warms up? If that unit runs fine untill it gets fully warmed up it could be starving for fire instead of fuel. A coil going bad will run fine from cold start up but once hot it acts up...


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## Knuckles (Aug 31, 2009)

THALL10326 said:


> Could be a coil, could be a carb. That stalling when hot comment needs to be described in a little more detail. *A bad carb causes problems from start up, not just after it warms up.* So, is this unit starving for fuel from start up or only after it warms up? If that unit runs fine untill it gets fully warmed up it could be starving for fire instead of fuel. A coil going bad will run fine from cold start up but once hot it acts up...



Right. That's my experience with *** carbs also. This one will start and you can actually use it for a little bit before it starts acting up. Suddenly you'll squeeze the trigger and it'll just bog down as if it's running out of gas. That's as best I can describe it.


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## Scooterbum (Aug 31, 2009)

Could be borderline compression also.


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## THALL10326 (Aug 31, 2009)

Knuckles said:


> Right. That's my experience with *** carbs also. This one will start and you can actually use it for a little bit before it starts acting up. Suddenly you'll squeeze the trigger and it'll just bog down as if it's running out of gas. That's as best I can describe it.



Welp if its the carb and its starts stalling after fully warm try closing the choke some and see if it picks back up. That will forced feed it fuel. If it still shuts down, stalls, won't restart untill the unit cools off thats the sign of a coil going bad. Don't fret, a coil is cheaper than the carb and very easy to put on. Being its a 1995 model what you describe points more to a coil than a carb. Try the choke and see what it does. If it does pick right back up and run you will know for sure its starving for fuel in which you replace the carb.


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## THALL10326 (Aug 31, 2009)

Scooterbum said:


> Could be borderline compression also.



Very good point. Its a 1995 model so its got some age on it. I would pull the muffler for a look see as well. I've seen many FS80's scored bigtime and still run full throttle but will not idle. Landscapers love those units, hard to kill...


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## Knuckles (Sep 1, 2009)

I'm embarassed, but I got it fixed.

3 yrs ago I borrowed said trimmer. I noticed it had a cracked gas tank. So, being a good son, I replaced the tank and fuel lines. Filled it with gas, ran it a minute or 2, then gave it back to my dad.

Talked to dad today. Says he hasn't ran it much since then because it acts like it starves for gas. (he has a homeowner trimmer for around the house. The FS80 he uses for heavy brush.)

I started checking things I'd replaced and discovered that fuel lines float.

Anyone guess what I forgot to install _inside_ the gas tank, 3 yrs ago?


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## THALL10326 (Sep 1, 2009)

Knuckles said:


> I'm embarassed, but I got it fixed.
> 
> 3 yrs ago I borrowed said trimmer. I noticed it had a cracked gas tank. So, being a good son, I replaced the tank and fuel lines. Filled it with gas, ran it a minute or 2, then gave it back to my dad.
> 
> ...



Yup, the filter. Gotta put that back in there...


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