Power down? and blue smoke on my trimmer...

Discussion in 'Mechanic and Repair' started by vomeisentor, Oct 21, 2009.

  1. vomeisentor

    vomeisentor LawnSite Member
    Messages: 23

    I have a STIHL FS85 and was running fine. Well, I poured in bit of Seaforam into the 50:1 mix in the tank and cranked the machine after 10 min. or so. The machine started up just fine except blue smoke came out at the start up, then got improved during operation, then came out more during idle. The engine also seems to sound and work weaker....

    For the smoke: I probably put too much oil in it, so I poured the gas out, put the regular mix of engine oil in. But it still did not fix the problem. I let it run for a while, but no improvement. Tip here ??

    For the power: There are TWO Carburetor adjusters. One for Low speed screw and LA IDLE speed screw. I played it with it and now the engine power does not seems to kick power once it had when I go full throttle. I do not have the manual for this model, but looked it up on line, the diagram of the F85 on the manual looks different than mine. It has three (HIGH, LOW speed screw, and LA (Idle speed screw). How do I adjust the right setting on mine?

  2. SunState Lawn Care inc

    SunState Lawn Care inc LawnSite Senior Member
    from Jax, FL
    Messages: 351

    If you have adjusted the carb and still bad try and Check your exhaust port it may be clogged up or if it has a screen over the exhaust like echo does clean the screen or just remove it totaly. I remove mine after they clogand have NEVER had any problems with the after removing the screen.
  3. RonAyersMotorsports

    RonAyersMotorsports LawnSite Senior Member
    Messages: 854

    Factory settings for H speed and L speed screws on a FS85 is 1 turn out. If anything different well you just really have to have an ear and know how to set these carbs. Check the exhaust port first. If clogged then clean. Then restart. Turn H screw in slowly with throttle wide open while running. If engine trys to stall out or run out of fuel open until unit runs at wide open speed. Once achieved turn it just slightly out past to make it a little rich (unit will sputter slightly). Now if unit won't idle then turn LA screw or idle screw in until it does. Now do the same process with the L screw as before with the H. Don't touch the H screw now. Then turn LA screw back out until unit is able to idle and cutting head won't turn. This is a much easier process to show than describe sorry.

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