Building the Solo 665 Hybrid!!!

[Miller Mod Saws]

Well boys I wanna do a kinda build thread on this saw. I'm really enjoying working on these and been playing with them in between my other builds. I wanted to show ya where I was at and open it up for thought and discussions. I know @Mastermind is getting ready to do some playing on these so hopefully he jumps in here and gives us some knowledge! So let's start with a vid of where there at now!

 

[Miller Mod Saws]

 

[Miller Mod Saws]

Let's start bye showing where I have them. I have worked up to where I have these saws now. So I'm gonna compare them directly. And not do the work up but bye all means ask away if ya have questions.

 

[Miller Mod Saws]

Saw 1 in the vid is running 1 base gasket and the numbers are 98/126 mains-128 secondaries and an 81 degree intake. This saw was running around 230 comp after a couple tanks of gas. When I tore it back down I opened up the squish a little and came out from the cylinder walls flat for about 3mm then angled it into the combustion chamber at a 2° angle to drop it just a tad. This was Randys idea so no credit on my end. I will check comp tomorrow. This saw is also running a flatter roofed exhaust

 

[Miller Mod Saws]

The second saw is running 2 base gaskets. The exhaust roof is more domed. Running g 220 comp after a couple tanks of fuel. 98/126 mains-128 secondaries/79 intake. Both saws are running the unlimited 272xp coil mod as well.

 

[Miller Mod Saws]

As I was building these my first saw I ported just like I would a 7910 and it just didn't have it. As I was playing I raised the exhaust. They seem to like a higher exhaust than a 7910. So this is where I'm gonna stop and open this up for debate!

 

[Miller Mod Saws]

I really like how both of these saws are running! That said as you can see in the vid the 79 intake is a tad stronger.

So here the question.

Why does the 665 hybrid like a higher exhaust?

Is it the longer stroke?

Hmmmm! Lol

 

[Mastermind]

I'm thinking it is because of the stroke. Even with the exhaust at 98°, I think it still has about 26mm from the squish band down to the top of the exhaust port. That means you can run a higher duration and still have plenty of trapped compression. That also means you are further along in the down stroke (crank angle) before the exhaust opens and pressure is lost.

Stroke changes everything.

 

[Miller Mod Saws]

I'm thinking it is because of the stroke. Even with the exhaust at 98°, I think it still has about 26mm from the squish band down to the top of the exhaust port. That means you can run a higher duration and still have plenty of trapped compression. That also means you are further along in the down stroke (crank angle) before the exhaust opens and pressure is lost.

Stroke changes everything.

Thank you my man. I've really enjoyed out conversations on this saw. Wait I enjoy all our conversations.

Let's see if we can twist some minds.

O wait mine will be the first. Lol.

 

[bryanr2]

watching the video, Im getting excited about getting mine back.

 

[huskihl]

37mm stroke on a 665?

 

[Miller Mod Saws]

37mm stroke on a 665?

Well good question. I've never measured it. But if you use a bore/stroke calculator one roughly has a 36.5 stroke the other 37.5. That's 1mm longer stroke or .5mm throw. Now that said running just one base gasket you have to take around 1.5mm(.058") out of the squish band for the cylinder to fit down on there. If some one has a link to a good calculator fill me in. Stock specs are 80.7cc on the 681 solo and 78.5cc on the 7910.

 

[awol]

The Dolmars have a 37mm stroke, and the Solo has a 38mm stroke. I only know this after having they're cranks chucked between centers in a lathe.

 

[Miller Mod Saws]

The Dolmars have a 37mm stroke, and the Solo has a 38mm stroke. I only know this after having they're cranks chucked between centers in a lathe.

Excellent. Thank you!

 

[Tractorsaw1]

Just need HSL to come out with the unlimited coil & the solo crank to really be in tall cotton!

Are the videos with the factory carb?

 

[Miller Mod Saws]

Just need HSL to come out with the unlimited coil & the solo crank to really be in tall cotton!

Are the videos with the factory carb?

Yes sir. I have some intake boots on the way now to see what I wanna do with the rwj4 carb!

 

[David Young]

how does the 65 cc jug compare?

 

[Miller Mod Saws]

how does the 65 cc jug compare?

This is saw #1 in the video above before I tore back into it and a stock 665!

 

[mdavlee]

I'd keep going on the exhaust.

 

[Miller Mod Saws]

I'd keep going on the exhaust.

But I'm scared.

I've thought about in the slower saw doing 96/126/and epoxy the intake back up to 79!