How To Use A Dolmar 7910 Top End On A Solo 665

[Mastermind]

Really simple stuff here fellers.....

The victim......a NOS Solo 665.







The top end.....



I like the 7910 top end on this saw for a few reasons.

For one thing, the 7910 uses the new style light weight piston.



This piston seems to increase transfer....and that's a good thing.

Now the Solo 665 had a 2mm longer stroke than the 7910, so you have a couple of choices. You can use a spacer under the jug, or you can cut the squish.

I chose to cut the squish. I'm building this saw as a 20" 8 pin rim saw. Not a cant cutting toy, but as a working saw that will be used in medium sized wood. By cutting the squish I was able to increase compression, and keep the cylinder base at the factory thickness for strength. I also like the way the timing numbers work out that way.

Now I took .060" out of the squish band, and used a Dolmar base gasket. The Dolmar base gasket is rubber coated metal VS the paper type gasket in the Solo. With that gasket in place the squish clearance is .018".

 

[Mastermind]

Now......let's compare the Solo jug to a Dolmar 6400 jug.

The Solo is a closed port design.





The Dolmar 6400 is an open port design.

 

[Warped5]

I chose to cut the squish. I'm building this saw as a 20" 8 pin rim saw. Not a cant cutting toy, but as a working saw that will be used in medium sized wood.

So why bother burning through time and money on this?

 

[weedkilla]

So why bother burning through time and money on this?

Really?

 

[Mastermind]

Now, here's a few pics of a stock 7910 jug VS the ported 7910 jug.

The stock exhaust is tiny.

 

[Mastermind]

So why bother burning through time and money on this?

Well Ted.......I'm doing my best to give the feller that this saw belongs to exactly what he asked for.

 

[Mastermind]

Now.......the exhaust after opening up.

 

[Mastermind]

The stock intake is also pretty small.



And after some grinding...

 

[weedkilla]

Now.......the exhaust after opening up.

On that last pic - have you completely removed the anti reversion lip/step on the top and sides and just blended it smooth on the bottom? But kept the floor height at stock?

 

[Mastermind]

Anyway.......this thread ain't really about porting. It's just to help someone get an available top end on an older saw should they choose to do so.

 

[rburg]

Is this the 665 you owned at one time or is it a different saw? The Solo is definitely a good looking saw.

 

[Mastermind]

On that last pic - have you completely removed the anti reversion lip/step on the top and sides and just blended it smooth on the bottom? But kept the floor height at stock?

That really ain't an anti-reversion lip. It just allows that weird 7910 muffler to mate with the exhaust port.

But yeah......I raised the exhaust and widened it enough to remove all that on the sides and top. If I lowered it any at all I would be seeing the piston begin to free port at the floor of the exhaust.

 

[Mastermind]

Is this the 665 you owned at one time or is it a different saw? The Solo is definitely a good looking saw.

Yep.....this is the one I've had for a couple of years. It's found a new home though.

 

[Mastermind]

On that last pic - have you completely removed the anti reversion lip/step on the top and sides and just blended it smooth on the bottom? But kept the floor height at stock?

Here's a pic of the 7910 muffler......you'll see what I mean.

 

[weedkilla]

That really ain't an anti-reversion lip. It just allows that weird 7910 muffler to mate with the exhaust port.

But yeah......I raised the exhaust and widened it enough to remove all that on the sides and top. If I lowered it any at all I would be seeing the piston begin to free port at the floor of the exhaust.

Thanks, that was what I was figuring. And thanks for correcting me on that lip.

 

[Stihl working hard]

Now.......the exhaust after opening up.

Great pics as usual Randy very informative

 

[Mastermind]

This thread was a dud LMAO.

 

[glock37]

Like a fart in a elevator ?


Sent from my iPhone using Tapatalk

 

[cgraham1]

This thread was a dud LMAO.

I liked it. Thank you, Randy.

 

[weedkilla]

This thread was a dud LMAO.

Re name it - masterminds 7910 with stroker crank build.