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#Post#: 6102--------------------------------------------------
Dolmar 7900 Porting Info
DIR By: Mastermind
Date: December 30, 2011, 12:11 am
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Hello guys. I see a lot of knowledgeable folks hanging out here.
Thought I might try to get a discussion going on building the
7900. I've never done one, and am intrigued with this saw
because of the many things I've heard about them.
1. The skirts are not very wide.
2. Many different piston can be used with a spacer.
3. They "like" a bunch of blowdown.
I do plan to build one soon and would like to glean some
knowledge from folks that have some experience with this model.
#Post#: 6207--------------------------------------------------
Re: Dolmar 7900 Porting Info
DIR By: rms61moparman
Date: January 2, 2012, 6:16 pm
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Have you tried finger ports yet Randy??
One of the most impressive 7900s I've seen is finger ported and
is is a butt kicker and name taker!
Mike
#Post#: 6208--------------------------------------------------
Re: Dolmar 7900 Porting Info
DIR By: Mastermind
Date: January 2, 2012, 6:24 pm
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I've not tried finger ports YET. I do need to do that though.
#Post#: 6210--------------------------------------------------
Re: Dolmar 7900 Porting Info
DIR By: rgclmc
Date: January 2, 2012, 6:32 pm
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What does blowdown refer to?
#Post#: 6214--------------------------------------------------
Re: Dolmar 7900 Porting Info
DIR By: Chainsawrepair
Date: January 2, 2012, 6:45 pm
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The one I had had finger ports put in it by Dave Neiger. That
saw was the best running 7900 I ran back in 07-09 till these new
ones are coming out like ginks.
#Post#: 6220--------------------------------------------------
Re: Dolmar 7900 Porting Info
DIR By: Mastermind
Date: January 2, 2012, 10:34 pm
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What does blowdown refer to?
It's the time from the exhaust port opens until the transfer
ports open.
I remember when Frank's saw was built. I would like to run that
puppy. :)
#Post#: 6338--------------------------------------------------
Re: Dolmar 7900 Porting Info
DIR By: rms61moparman
Date: January 5, 2012, 5:35 pm
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Well Randy,
I've got a couple of..."candidates" around here if you start
thinking you want to practice.
How about a BB 7900?
Mike
#Post#: 6339--------------------------------------------------
Re: Dolmar 7900 Porting Info
DIR By: Mastermind
Date: January 5, 2012, 5:55 pm
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I have one on the way and two others in the wings. I just wonder
if finger ports are the way to go on these saws? ;D
For you though Mike........anything my friend.
#Post#: 6355--------------------------------------------------
Re: Dolmar 7900 Porting Info
DIR By: EHP
Date: January 5, 2012, 8:30 pm
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see that is where you get into trouble , are these real worksaws
or run a couple tanks a year cutting wood or cookies and are
called worksaws , If the saw is going to be run 8 plus hours a
day 5 or 6 days a week and is to last 2000 hours plus then
finger ports are not the way to go , One thing I have built and
that is alot of 7900's , I even built 4- 7300/7900 for Dolmar
themselves with 3 of those going to Africa , 7900 to me is a
great saw and I like them alot , the only thing I change is the
ring , I like the husky ring better and I feel it stands up
better . Now on the saws for dolmar I had to use their piston
and their coil setup so that limits you alot right there cause
the 7900 sure is a narrow skirted piston so ports are narrow as
well . These saws they are putting different pistons in that
makes you build a spacer plate and lots of other stuff is not
what I call a worksaw , Reason for so much blow down is the
crankcase volume is very tight on them , if you raise the
transfers up like on a ported 372 it will lay down in the cut
once you put it under load , I'm talking like cutting 20 plus
inch stuff
#Post#: 6356--------------------------------------------------
Re: Dolmar 7900 Porting Info
DIR By: Mastermind
Date: January 5, 2012, 8:36 pm
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That's the stuff I'm looking for on this. I've built more than a
few saws, but the 7900 is new to me.
The saw I'm thinking about will be more of a GTG saw than an
everyday worksaw, so.....
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