Dolmar 64xx/73xx/79xx series, smurfs and solo 665/675/681 thread

[Big1066ih]

I like a 372, a 7900 feels like a 372 with more grunt.

I'll take my mmws 372oe over the bigbore 6421 anyday for cutting firewood. Although the porter of the bigbore could be why I feel that way

 

[Hedgerow]

Case compression can make or break a saw. I am a firm believer of how the direction of scavenging loop effects more than velocity.

Case in point, I have added a fairly thick spacer to run a certain piston in a 7900. One would think it would have blown case volume way out. BD in the range of 26-29.

Made for a solid, wide band 5 cube.

There’s some “feel” in that area.

Case compression is good in some saws to a point, then backwards you go:.

A fast saw should feel “free”, and loose..

Quick from mid to top, but not necessarily from idle to mid..

It’s hard to explain.

Don’t need 200 lbs of comp to get there either.

Though 200 lbs of comp works great in most work saws though.

 

[Hedgerow]

I’m really starting to like this stock 390 I got from some guy out east back at the GTG..

I opened up the exhaust a little, and added some fuel.

Such an improvement over the 660..

 

[Hedgerow]

Seems like a lot of compression for a stocker.

 

[huskyboy]

Why would it pop? Lol
A properly maintained saw shouldn't pop. Lol

The av mount on the cylinder to the handlebar of the older 7900’s was a known weak point supposedly if pinched and yanked on or running a long bar. The newer improved style has a limiter built into it. “Popping” the av mount is what I meant. “Popping” from too much advance is a different thing all together.

 

[huskyboy]

I'll take my mmws 372oe over the bigbore 6421 anyday for cutting firewood. Although the porter of the bigbore could be why I feel that way

The am cylinders don’t run as good as oem. I’ve owned a ported 372xpw and ported 365 special myself. Great saws, but the 7900 is a improvement over both of them.

 

[Hedgerow]

The am cylinders don’t run as good as oem. I’ve owned a ported 372xpw and ported 365 special myself. Great saws, but the 7900 is a improvement over both of them.

It takes a special 7900 to whip a proper 50mm 372 in the 5 cube class.

Husky’s are runners.

 

[huskyboy]

It takes a special 7900 to whip a proper 50mm 372 in the 5 cube class.

Husky’s are runners.

I’m talking worksaws, not square wood racing. I do understand where your coming from though. There is a lot of potential in a 372 for that.

 

[Hedgerow]

I’m talking worksaws, not square wood racing. I do understand where your coming from though. There is a lot of potential in a 372 for that.

A few years ago there was a 066/660 build off...

IIRC, there was a 365 special that slapped the 36” bar on and beat most of them..

Not the top one, but most of em...

Maybe I’m remembering wrong..

 

[Hedgerow]

Oh, and HP is HP...

It’s up to the operator to make it how he wants it.

Gear it up , gear it down..

Chain it, etc...

 

[RI Chevy]

Your giving away all your secrets. LOL

 

[huskyboy]

A chain/sprocket makes or breaks a saw for sure. As does tune.

 

[Hedgerow]

Your giving away all your secrets. LOL

No, trust me..

There’s a lot of running/ tuning / feeling, to be done just getting there... few are those who find it..

 

[TreeLife]

No, trust me..

There’s a lot of running/ tuning / feeling, to be done just getting there... few are those who find it..

It's an art, to complete and compliment the powerhead...

 

[wcorey]

Does the newer 7910 slab side piston have more case compression than the windowed 7900 piston?

Are you thinking along the lines of that it's lighter and therefore reasonable to assume it displaces less volume or that since it's non windowed it's somehow taking advantage of the upside down cup pushed into water thing?
Or none of the above...

I seem to remember back a ways some discussion on this or a similar subject but either way I kinda don't get how the two pistons would have much of a differing effect on case comp.

 

[huskyboy]

Are you thinking along the lines of that it's lighter and therefore reasonable to assume it displaces less volume or that since it's non windowed it's somehow taking advantage of the upside down cup pushed into water thing?
Or none of the above...

I seem to remember back a ways some discussion on this or a similar subject but either way I kinda don't get how the two pistons would have much of a differing effect on case comp.

The upside down cup thingy

 

[wcorey]

The upside down cup thingy

Yah, that's a tough one to get your head around.
I tend to think it has no bearing in this particular instance but it's hard to explain why.

 

[Hedgerow]

The upside down cup thingy

There’s much re to it than that...

Those windows give way to a fuel source.

But hey, there’s more going on there than that.

 

[Big1066ih]

Oh, and HP is HP...

It’s up to the operator to make it how he wants it.

Gear it up , gear it down..

Chain it, etc...

No arguing it comes down to operator when its square wood. I inarguably had the fastest saws and chains at our little gtg today but I SUCK lol so...i got beat.

 

[Hedgerow]

No arguing it comes down to operator when its square wood. I inarguably had the fastest saws and chains at our little gtg today but I SUCK lol so...i got beat.

Sharpen those chains...

Gear em right...