Stihl FS 110 trimmer bogging out.

[Green Zone]

I have had this trimmer for many years. This year it has been bogging out. Acts like the exaust is pluged but the screen is clear. So the cutting head just barely turns at full throttle. I needed to just clean up a small area so I run it. Before I got done it just came to life and worked like it should. Thought my problem was solved. Took it out on a job and the same thing works bad for a few minutes then comes to life and is fine for as long at needed. Tried it again today same process. Suddenly comes alive after 3-5 minutes of just barely running. New spark plug, clean air filter, tried it with no filter same issue. So it works bad, then suddenly good. Any ideas??
So if you can imagine if it was flooding then cleared up it would pick performance over a few seconds. But this in instant from bad to good. Thinking electrical.

 

[bertsmobile1]

Remove the muffler and check for carbon fouling the exhaust port.

 

[Green Zone]

Remove the muffler and check for carbon fouling the exhaust port.

Correct me if I am wrong, but it would not work good if the port was plugged. It would be a continuous problem. This is not continuous. It clears up on it's own and works fine.

 

[Fish]

Are you sure that this bogging is not from a clutch drum bearing going bad and locking up off and on?

When it starts bogging again, shut it off, and then turn the trimmer head by hand, and note any resistance and/or noise.

 

[StarTech]

Can be also be Crankcase seals leaking

 

[bertsmobile1]

Depends upon how much build up is in there.
As always we are trying to make a diagnosis based on the words you typed which is quite difficult.
So if you want me to elp you, pull the muffler off
While you are there check the piston rings for scoring & the cylinder wall on the other side.
If you don't want help from me then don't do it.
I have a simple rule that I work under on this ( and other ) forums.
I ask people questions
If they don't provide the answers, I don't bother to ask any more questions till they do.

From what you have typed it could be a lot of silly things but I have assumed that you know the difference in the sound of an engine that is choking on it's own exhaust, one that is dieing lean & one that is dieing rich .
You said it seemed to be choking as if the screen was blocked but the screen was not blocked
Well the next thing back from the screen is the exhaust port
While the muffler is off give it a shake and see is some foreign bodies fall out.

 

[StarTech]

This is a 4180 4-mix engine. So even though you use two cycle mix it is actually a four cycle engine.

Also make sure the valves are adjusted to specs (New gasket is required when adjusting the valves) and that you are not having carburetor problem due stiffening of the metering diaphragm or loose impulse hose.

 

[Green Zone]

Depends upon how much build up is in there.
As always we are trying to make a diagnosis based on the words you typed which is quite difficult.
So if you want me to elp you, pull the muffler off
While you are there check the piston rings for scoring & the cylinder wall on the other side.
If you don't want help from me then don't do it.
I have a simple rule that I work under on this ( and other ) forums.
I ask people questions
If they don't provide the answers, I don't bother to ask any more questions till they do.

From what you have typed it could be a lot of silly things but I have assumed that you know the difference in the sound of an engine that is choking on it's own exhaust, one that is dieing lean & one that is dieing rich .
You said it seemed to be choking as if the screen was blocked but the screen was not blocked
Well the next thing back from the screen is the exhaust port
While the muffler is off give it a shake and see is some foreign bodies fall out.

Thanks, I am sure you know more about this engine than I. Because I know nothing. I can remove the muffler and check the exaust port for build up. But the idea of a loose part in the exaust is a good idea. Thanks for trying to help me.

 

[Green Zone]

This is a 4180 4-mix engine. So even though you use two cycle mix it is actually a four cycle engine.

Also make sure the valves are adjusted to specs (New gasket is required when adjusting the valves) and that you are not having carburetor problem due stiffening of the metering diaphragm or loose impulse hose.

Star Tech, thank you for the reply. When I get to adjusting of valves, that is something the dealer will need to do. The difficult part of my problem is the trimmer works perfect after first 3- 5 minutes of poor performance.

 

[StarTech]

You can that yourself but you need the kil from Stihl as it a special feeler gauge in the kit. PN 4180 007 1005.