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#Post#: 47961--------------------------------------------------
Converting Solo 665 to a 681
By: KilliansRedLeo Date: October 16, 2014, 12:03 pm
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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.
DexterDay 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.
Dexter is going to covert one of his 665s to a 681 using a new
OEM Solo P/C kit. I measured the two pistons and the deminsions
of the pistons are the same except the weight, the slab sided
Dolmar is a little lighter than the windowed Solo.
I read somewhere that a couple of builders favored this route on
the Dolmar 7900 but I have no specific knowledge or opinion on
how the piston would perform in a stock 681 saw. Any thoughts?
???
#Post#: 47970--------------------------------------------------
Re: Converting Solo 665 to a 681
By: aclarke Date: October 16, 2014, 3:10 pm
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Tim, i'd go lighter in the reciprocating mass, I.e piston, rod,
etc. I can't See any advantage to a heavier piston . Slab side
is 15 grams or so lighter. Maybe use a stihl double butted pin
(tapered internally) Adding mass to the rotating flywheel could
be a hindrance or help. It's gonna take power to accelerate the
heavier mass so in cases like a hot start saw race where you can
spin up the mass prior to hitting the wood where the stored
energy could be utilized. Real world use it would be a wash IMHO
#Post#: 48051--------------------------------------------------
Re: Converting Solo 665 to a 681
By: KilliansRedLeo Date: October 18, 2014, 11:24 am
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Thanks Adam, any Idea which Stihl wrist pin?
#Post#: 48058--------------------------------------------------
Re: Converting Solo 665 to a 681
By: aclarke Date: October 18, 2014, 7:03 pm
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I'll check in a few and get back. ..
#Post#: 48073--------------------------------------------------
Re: Converting Solo 665 to a 681
By: farmboy Date: October 18, 2014, 9:10 pm
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I wanted to use the slab piston in my 665/681. Cut the wrong
side on intake port had to use AM windowed piston ring pin in
center. Plan on sending slab piston out to relocate pin to the
center. Don't know why Dolmar put the ring locating pin on the
side on the slab piston. IIRC the slab piston skirt is about
2mm wider than windowed piston.
Shep
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