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jpbush316
09-07-2011, 10:49 PM
I have a Stilhl fs90 that starts up fine, runs fine on idle but once the throttle is pulled it starts to sputter. Took it to repair shop and he put a new carb kit on it and cleaned out the muffler. Said compression was a little low, although the other mech thought it was good. Get home and try to use it and it's still doing the same thing. I'm stumped. Maybe a gas line issue? Any ideas?

themadcutter
09-07-2011, 11:57 PM
I am betting the coil. I had a fs110 that pretty much did the same thing (may have been a 130). I asked my shop guy about it and he said coil so I put one in and he was right.

2stroked
09-09-2011, 09:06 PM
I'm guessing coil also.

Shawn S
09-09-2011, 09:38 PM
My Stihl blower was doing the same thing last week. I pulled the spark arrestor and cleaned it up and the thing runs better than ever.
I would assume your trimmer probably has one too.

themadcutter
09-09-2011, 10:37 PM
My Stihl blower was doing the same thing last week. I pulled the spark arrestor and cleaned it up and the thing runs better than ever.
I would assume your trimmer probably has one too.


Yea I would check the spark arrestor first because its easiest. I ruled it out first on my trimmer.

2stroked
09-09-2011, 11:04 PM
Yea I would check the spark arrestor first because its easiest. I ruled it out first on my trimmer.

I'm guessing when it says that the dealer cleaned the muffler he also checked the spark arrestor.

themadcutter
09-09-2011, 11:33 PM
I'm guessing when it says that the dealer cleaned the muffler he also checked the spark arrestor.

That would probably be a very safe bet. I forgot the OP said that.

Shawn S
09-10-2011, 12:42 AM
I'm guessing when it says that the dealer cleaned the muffler he also checked the spark arrestor.

You would hope wouldn't you?? Since it was at the dealer we can also guess it was repaired correct? It seems that didn't happen. Who is the one back there in the dealer doing the work? Is it the guy who has been there 30 years and knows these things in and out, or the guy who started yesterday and has no idea what a spark arrestor is? :laugh:

I still say check the spark arrestor. Heck, just take it off and start it, if it runs good you know that's your problem. Clean it up and put it back on.

Always start with the simple stuff, and never assume the guy before has done anything unless you watched them do it.

unkownfl
09-10-2011, 12:43 AM
Sounds like carb is bad or dirty. Those are very tiny jets in there. Normally the coil just goes out and doesn't work at all. The coil doesn't know if the engine is under load or not unless its blowing the spark out because its to weak which I doubt.

themadcutter
09-10-2011, 12:48 AM
Sounds like carb is bad or dirty. Those are very tiny jets in there. Normally the coil just goes out and doesn't work at all. The coil doesn't know if the engine is under load or not unless its blowing the spark out because its to weak which I doubt.

I used to think that about coils but have since learned that they can be intermittent and sometimes just weak. I have even heard of some on chain saws that have some kind of rev limiter in them.

Mine would idol, though a little rough, and sputter out when I gave it the gas. The coil fixed it.

It could be the carb also. no doubt about that. but usually if its the carb i find it will die after a few seconds of full throttle. But thats probably not a hard and fast rule either.

unkownfl
09-10-2011, 12:59 AM
I used to think that about coils but have since learned that they can be intermittent and sometimes just weak. I have even heard of some on chain saws that have some kind of rev limiter in them.

Mine would idol, though a little rough, and sputter out when I gave it the gas. The coil fixed it.

It could be the carb also. no doubt about that. but usually if its the carb i find it will die after a few seconds of full throttle. But thats probably not a hard and fast rule either.

Usually, the coil will only be intermittent if its humid or the coil is hot. I did say normally. You can take the coil off another Stihl product and put it on there to test it. It's pretty easy to swap and most of the Stihl stuff use the same coil.