Author Topic: Dolmar 7900 Porting Info  (Read 3789 times)

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Offline Mastermind

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Dolmar 7900 Porting Info
« on: December 30, 2011, 01:11:36 am »
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.
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Offline rms61moparman

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Re: Dolmar 7900 Porting Info
« Reply #1 on: January 02, 2012, 07:16:47 pm »
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

Offline Mastermind

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Re: Dolmar 7900 Porting Info
« Reply #2 on: January 02, 2012, 07:24:41 pm »
I've not tried finger ports YET. I do need to do that though.
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Offline rgclmc

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Re: Dolmar 7900 Porting Info
« Reply #3 on: January 02, 2012, 07:32:21 pm »
What does blowdown refer to?

Offline Cut4fun .

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Re: Dolmar 7900 Porting Info
« Reply #4 on: January 02, 2012, 07:45:47 pm »
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.
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Offline Mastermind

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Re: Dolmar 7900 Porting Info
« Reply #5 on: January 02, 2012, 11:34:07 pm »
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. :)
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Offline rms61moparman

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Re: Dolmar 7900 Porting Info
« Reply #6 on: January 05, 2012, 06:35:33 pm »
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

Offline Mastermind

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Re: Dolmar 7900 Porting Info
« Reply #7 on: January 05, 2012, 06:55:28 pm »
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.
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Offline EHP

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Re: Dolmar 7900 Porting Info
« Reply #8 on: January 05, 2012, 09:30:01 pm »
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

Offline Mastermind

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Re: Dolmar 7900 Porting Info
« Reply #9 on: January 05, 2012, 09:36:38 pm »
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.....
Mastermind Work Saws
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