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Still 661

Discussion in 'Milling & Saw Mills' started by chief1911, May 16, 2018.

  1. chief1911

    chief1911 ArboristSite Lurker

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    I have milled a couple logs with my new 661. It has the m Tronic setup. Everyone advises to run the saw lean when milling. I see why that is so. The theory is, if I calibrate the saw on 50:1 ratio, then to run it a little rich I can just add more oil to make it rich, like 40:1. Please correct me if I am wrong, or has anyone else done this?

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  2. stihlaficionado

    stihlaficionado God of ArboristSite

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    Lean when milling? I always thought it was rich when milling as the conrod bearing needs all the lube it can get
     
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  3. BobL

    BobL No longer addicted to AS

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    You have got this, as we say here isn Oz, completely arsed about in 2 directions.

    Firstly running the saw has to be run RICH not lean. This means adjusting the fuel mix to air ratio using the carby H screw.
    If you run it lean you will burn it out.

    You can run with any GAS to LUBE ratio you like but once you choose this, only THEN should you set the carby so that the saw runs rich.
    If you change the gas to lube ratio you should retune the Mix to Air ratio again.
     
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  4. Brian72

    Brian72 ArboristSite Guru

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    For milling, you want to run rich. Being m-tronic, you can't adjust the carb. Running 40-1 will get you more oil for some extra protection (I think some even run 32-1.) The saw will adjust itself to whatever mix you put in.

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  5. andy at clover

    andy at clover Woods!

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    You might read through this thread OP.

    It seems like the 661 was designed around (and for) 50:1 fuel.
    The Saw Tech at my nearest shop insists that the 661 M-tronic will be most capable of maximizing performance running 50:1.
    It's designed for 50:1 and will make it's calculations assuming that ratio.
    Use Stihl HP oil ( or similar synthetic) and 92+ Ethanol Free fuel whenever possible.


    Here is the number he gave to think about.
    With a full tank in the 661. The volume of oil difference between 50:1 vs 40:1 is about 4mls per tank (less than a teaspoon.)
    How much of those 4mls is in the crankcase at any given moment during operation?
    The M-tronic actively decides the air:fuel mixture. Giving that "chip" the best chance to perform seems to make sense.
     
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