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My trusty Stihl has let me down

Discussion in 'Lawn Mowing' started by Envy Lawn Service, Jul 6, 2005.

  1. Envy Lawn Service

    Envy Lawn Service LawnSite Fanatic
    Messages: 11,087

    Well, as always, it seems that all my stuff all breaks down at the same time and it always picks the worst possible time. A few weeks back, all the mowers broke the same day and on that same day my regular use 2 cycle stuff started getting stubborn on me.

    Well, now it is yesterday, but my trusty Stihl trimmer laid down on me, and so did the Echo blower. Errr! Well anyways, about the same thing happened to me less than a year ago. Before they would crank and then act like they were running out of gas and die. Well, that mystery turned out to be the fuel lines. I replaced it all on both.

    Now, this time around, both will crank and run, but neither will accelerate. They just choke, fall on their face and die if I don't let off quick enough. They were both also a little stubborn to prime. The lines seem ok. So I figured it was a good time to go ahead and change the fuel filters and air filters.

    I did this to the Echo first and it didn't help. But during the process of messing with it I decided to mess with the high speed screw. After running it up and down within it's capped limits a few times, it cleared right up and now runs fine.

    My stihl trimmer on the other hand is a different story. I changed out the filters and set all the carb screws to spec. I even removed the muffler to clean the carbon from the exhaust ports. There was nothing reall there but a little gumming around the edges, which I cleared and put it back together. But it still would not accelerate. The high speed screw will only adjust 3/4 of a turn within it's capped limits and does not help. But the low speed screw has a lot of adjustablity. No capped limits. So I ran it out farther and farther. Finally I got it working. I used a full tank of gas and when I stopped to refuel, it went right back to the same thing. I've messed with it and messed with it. I can't get it going.

    But as a side note, while changing the filters out, I spilled some of the gas out of the tank onto the floor. I stood in it while working a bit more and when I stopped to clean it up, I realized it had melted the rubber soles of my sneakers!!!!! Rubber just rolled right off when I wiped the bottom of my shoes!

    What in the heck gives with that????? If it did that to my shoes, geez then, what is it doing to my fuel lines???? And why would the gas be doing that?

    I'm not sure what to think now. Is this my problem? Is something else wrong? Or do I need to figure out how to remove the limit cap on the high speed screw? What?

    Not sure what to do and this sucks.
    It was already a short week and now I'm even further behind.
  2. Roger

    Roger LawnSite Fanatic
    Messages: 5,938

    My next door neighbor bought several items of power tools from the previous owner. One was a Stihl hedge trimmer, short shaft model. I believe it has the same power head as my FS85/FC85 tools, with a 22" double edged cutting bar. It may be the same power head as you have on your trimmer.

    He was having the same problem -- it ran, but would choke out when applying the throttle. He asked me about it, and I did the obvious things you did, but to no avail. My time was limited and I suggested the next step would be a carb inspection. I'm fuzzy on exactly what he did because we didn't see each other for a long time - schedules didn't mesh. But, I believe he either: (1) replaced the carb, or (2) rebuilt it with a new diaphram. He did get it running in a normal fashion.

    One more point - Before he got it fixed, I seemed to recall he could make it run faster, albeit not right, but usable to some extent, by running it with partial choke.
  3. mtdman

    mtdman LawnSite Gold Member
    Messages: 3,143

    DId you clean the spark arrestor screen on the muffler exhaust? If that gets carboned over, the trimmer won't accelerate or run properly. I always take those off, first thing, when I get a new piece of stihl equipment.
  4. Envy Lawn Service

    Envy Lawn Service LawnSite Fanatic
    Messages: 11,087


    I do the same thing. So that's not an issue. But what I did decide to do was just to call Stihl. Great informative guys. After talking with them I decided to go ahead and pull the lines to see how they looked once everything was laying out. Turns out the part of the line that was in the tank was very soft and swelled out.

    This time, I replaced this line with some different stuff. Same outside diameter, but smaller inside. So I also had to convert it over to an Echo fuel filter... which did not hurt my feelings at all because the Stihl fuel filters cost more than twice as much and have an aggrivating habit of floating so it looses fuel pickup when tilted, ect. While I was at it, I cleaned everything off and pulled the carb. I spray cleaned what I could without doing a full disassembly.

    I did get it back to going. But it is still very very tempermental after starting.
    It also will not run when tilted to either side.
  5. mtdman

    mtdman LawnSite Gold Member
    Messages: 3,143

    What model is it?
  6. lawnman_scott

    lawnman_scott LawnSite Fanatic
    Messages: 7,547

    If i have a problem like that I take the carb apart and spray it real good woth carb cleaner and it usually fixes the problem.
  7. Envy Lawn Service

    Envy Lawn Service LawnSite Fanatic
    Messages: 11,087

    It is an FS 85 R
  8. dishboy

    dishboy LawnSite Fanatic
    from zone 6
    Messages: 5,904

    At this point if it were me I would put a new diaphram in the carb as well as completely empty your fuel source and remix with fresh gas.
  9. scottishmaximus

    scottishmaximus LawnSite Senior Member
    from ohio
    Messages: 286

    Since you said your blower and trimmer are both having problems, I would try some new gas. Bad gas or too rich or lean of mix. You may want to check the inside of the muffler for a clog as well. Could bad gas be the culpret for your mower troubles?
  10. Envy Lawn Service

    Envy Lawn Service LawnSite Fanatic
    Messages: 11,087

    I was thinking the same thing since it chokes out when tilted.

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