In loving memory of Kenis D. Keathley 6/4/81 - 3/27/22 Loving father, husband, brother, friend and firewood hoarder Rest in peace, Dexterday

Solo 665 to 681 Conversion

Discussion in 'Chainsaws and Power Equipment' started by KilliansRedLeo, Oct 13, 2014.

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  1. Cut4fun

    Cut4fun

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    Corn farmers aren't worried. Free supply for their cost of planting and taking in. Unlimited supply on hand. Fed from outside straight to their heat source. Remember reading about it when I thought about doing it.

    I aint eating no field corn either. Been there tried that. :zip:
     
    Cut4fun, Oct 15, 2014
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  2. DexterDay

    DexterDay Administrator

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    My Pellet furnace will burn anything.

    But price was always the factor for me.

    Hijacked... My bad KRL ;)
     
    DexterDay, Oct 15, 2014
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  3. SquareFile

    SquareFile

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    You eat field corn in many different ways
     
    SquareFile, Oct 15, 2014
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  4. mdavlee

    mdavlee

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    Trying to quit all that.

    Dex hurry up and get this swap done. Are there going to be before after videos with timed cuts, weather condition, and barometric pressure that day:whistle:
     
    mdavlee, Oct 15, 2014
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  5. Cut4fun

    Cut4fun

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    Yep you did it and I ran with it. ;):whistle:
     
    Cut4fun, Oct 15, 2014
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  6. DexterDay

    DexterDay Administrator

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    Yeah Mike, I was gonna do just that.. Don't know about the pressure ;)

    But, it was gonna be as follows.

    Run 3 passes as is (65 cc) with 18" bar and chain.

    Then swap the tops and install 681 slug and jug
    Documenting and taking pics of all the steps. Then we will run a tank through it with a different bar and chain/20"/to help seat the rings and break it in a little.. And then make 3 passes with 18" bar and chain.

    Same Cant and try to make it the same day if at all possible.
     
    DexterDay, Oct 15, 2014
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  7. lukem

    lukem

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    My phone has a barometer...yours might too. Just sayin.
     
    lukem, Oct 15, 2014
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  8. DexterDay

    DexterDay Administrator

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    It does everything else.. Literally.
     
    DexterDay, Oct 15, 2014
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  9. mdavlee

    mdavlee

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    I was just picking about the temperature and pressure. If you do it in a day or two it shouldn't change the wood much unless it's frozen.I
     
    mdavlee, Oct 15, 2014
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  10. KilliansRedLeo

    KilliansRedLeo

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    OK guys, time for some advice. Dolmar changed the piston configuration for the 7900 from windowed to slab sided. Most think that the change made for better performance out of the 7900.

    Dexter and I were discussing using the new Dolmar 7900 piston in this project instead of the Solo windowed piston that comes in the Mahle OEM Solo 681 P/C kit.

    I read somewhere that a couple of builders favored this route but I have no specific knowledge or opinion on how the piston would perform in a stock 681 saw. Any thoughts?
     
    KilliansRedLeo, Oct 16, 2014
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  11. the GOAT

    the GOAT Banned

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    For the tests to be considered valid you need to make some cuts with a control saw before each run with the solo. ;)
     
    the GOAT, Oct 16, 2014
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  12. DexterDay

    DexterDay Administrator

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    You pick... ;)
     
    DexterDay, Oct 16, 2014
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  13. Aclarke

    Aclarke

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    Slab sided is much lighter. 15+ grams.

    Don't think the flow is compromised vs. The windowed piston. Also, less reciprocating mass will be a net gain, however small.
     
    Aclarke, Oct 16, 2014
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  14. the GOAT

    the GOAT Banned

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    the GOAT, Oct 16, 2014
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  15. KilliansRedLeo

    KilliansRedLeo

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    OK, Adam, I agree the reduction in reciprocating mass I believe would lead to higher RPMs, but also a corresponding loss in torque, do you think not?
     
    KilliansRedLeo, Oct 16, 2014
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  16. w8ye

    w8ye

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    The torque factor because of weight would come more into play from the external rim of the flywheel rather from the reciprocating piston weight.

    Then of course the counter balances on the crank will effect torque?
     
    w8ye, Oct 16, 2014
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  17. KilliansRedLeo

    KilliansRedLeo

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    Both good points! w8ye, OBTW what does w8ye stand for? Been thinking about that since I was on another site, still have not yet figured it out!
     
    KilliansRedLeo, Oct 16, 2014
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  18. mdavlee

    mdavlee

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    I know Randy prefers the slab sided. I've not done one with that piston. I hope to experiment with one sometime this winter.
     
    mdavlee, Oct 16, 2014
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  19. KilliansRedLeo

    KilliansRedLeo

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    Mike good point about Randy's preferences. I'm thinking that the slab sided piston may very well work much better when used in conjunction with porting the engine. However I'm not sure what it alone would do when used in a non-ported stock Solo 681. We do know that the stock timing numbers of the 7900/681 jugs are very close if not identical. So it stands to reason if Dolmar went to the slab sided piston, for a benefit known only to them; we could assume that benefit would also apply to the Solo. Could we not?
     
    KilliansRedLeo, Oct 16, 2014
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  20. mdavlee

    mdavlee

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    I would think it would benefit a stock saw as well.
     
    mdavlee, Oct 16, 2014
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