Modding the Dolmar 7900

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I ran Jd's Treemonkey 7900 at Wiggs last gtg, it was impressive to say the least. I havent ran a xpw yet that wanted any of it imo. Id like to have one myself one day.:rock:

And that saw has been improved upon since then...
The stumpkita of Andy's OWNED 2 XPW's at our spring GTG...
There are some good recipe's for the 7900's out there...
Plus they're just plain sexy...
And you cant port your way to SEXY!!!
:msp_tongue:
 
Sure, but there just isn't enough metal to work with, in some important places - at least that is how I understand it...

As I understand it, the 7900 is far from the most modification friendly saw ot there....:msp_wink:

Five years later and you are still spewing stuff that you have no personal experience with. Have you modded one of these? Have you had a modded 7900? :chatter: No picking on you, but really? Don't interject wtih he-said she-said stuff....

I have this new brick that is super lightweight and has carbon nitrade in it, so it drops trees like a light saber.
 
I ran Jd's Treemonkey 7900 at Wiggs last gtg, it was impressive to say the least. I havent ran a xpw yet that wanted any of it imo. Id like to have one myself one day.:rock:

And that 7900 beat over half of the 660 buildoff saws with the same bar and chain set up as them. Thanks again for letting me use your bar and chain.

I cut most of my wood with that saw. I may have to send my heated handle 7900 down to Scott.:hmm3grin2orange:
 
Because that's the way I choose to do it. I check stock squish, figure out how much I want to take out of the chamber then do a little math in my head on how much to take off the base after to achieve desired squish, just the way I do it.
I do it that way too, for two reasons.
1. The mandrel will find any ridge, burr etc and will also double check how perpendicular I cut the squish band in relation to the bore.
2. Cutting the base last makes it much easier to fine tune your squish. Cut, measure, cut again, easy peezy.
 
I do it that way too, for two reasons.
1. The mandrel will find any ridge, burr etc and will also double check how perpendicular I cut the squish band in relation to the bore.
2. Cutting the base last makes it much easier to fine tune your squish. Cut, measure, cut again, easy peezy.

Yup thanks Nik, exactly what I do, easy to slide the cylinder off the mandrel check squish, and slide it back on if a little more needs to come off. I learned my lesson the first time cutting a squish band, left a ridge, sucked when I had to set it back up again in the lathe, now I check very carefully after taking it off the lathe, I use a small flat blade screwdriver to feel for any ridge where I machined. This time I learned that my test indicator is a POS, I need to get a nice one, I bought a cheap one and well, that's what I got.

The build now is on hold till I get another piston. Not going to use the stock one, should be able to make it work fine, however I wish I would of known before I did the machine work, oh well.
 
The 7900 is one of my most valued saws. It always puts a smile on my face. Watching
 
Anyone have any experience with the new slab sided piston for the 7900? Is it worth the money to get? Does it give any advantages in skirt width?

Coming from the throttle end of this.

I have two modded 7900's with each piston setup.

To ME, I noticed no difference between the two. Chain makes more of a noticeable difference than teh guts when running them. :msp_thumbup:

Randy -

Sweet video BTW.
 
went to far already?

No, haven't done anything yet, just the machine work as I posted. I just got a inside tip on a good piston to try in the 7900, and I'm going to try it and see what happens, ordered the piston, hopefully will be here in a week.

What I meant was, I wish I knew about the piston swap before I did the machine work, since the crown height is a little different, but easy to overcome, will either take a little off the top of the piston or run a thicker gasket.
 
No, haven't done anything yet, just the machine work as I posted. I just got a inside tip on a good piston to try in the 7900, and I'm going to try it and see what happens, ordered the piston, hopefully will be here in a week.

What I meant was, I wish I knew about the piston swap before I did the machine work, since the crown height is a little different, but easy to overcome, will either take a little off the top of the piston or run a thicker gasket.


An 046 piston should fit . ;)
 
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