Mastermind Meets The MS661 C-M

[big t double]

.........
Now get this........the bore is 56mm, and the stroke is 37mm.
..........

so a larger bore and shorter stroke than a 660...does this drastically affect how it gets ported? only ask because im stupid.

 

[Mastermind]

It should make it handle poor fuel a little better......but that's all I can see.

The engineers that build these things are smart........real smart. They make me slow down and really look things over when I see a big change like this.

 

[mdavlee]

That's almost a copy of the 395 specs. The stroke on it is 38mm if I remember right.

 

[ELECT6845]

Good you seem a little grouchy here lately.

 

[Stihl working hard]

This post was the worst part of my day

Welp, Millie, Jon, and the grandkids are gonna go look at some Christmas lights. That's makes for a good time for the little wife and I to slip off alone.

happy wife happy life

 

[Buffhunter]

You can doooo it Randy!!!!! You can do it allll night longgg!!!!!

 

[ernurse]

Have a good night Randy...you deserve it. After all it's only a saw that we can't even get yet.

 

[bryanr2]

I think I'd rather get a brand spankin' new 2188 (ported) from/through MasterMind or Terry. Could probably also get a nice 32" Total bar with it for that price.

Sorry for the derail. Back to waitin' on Randy to have a 'productive' evening with his better 1/2...............and then put some more 661 teaser pics.

I like a 2188. I have a W model. Looking forward to seeing how they all stack up in "my hands" soon.

 

[wap13]

Bite me Neal. I've been damn busy.

Everyone want a piece it seems.

Timing numbers????

Exhaust: 98
Transfers: 123 - 128
Intake: 81

Now get this........the bore is 56mm, and the stroke is 37mm.

Working on the machine work now. I'm taking my wife out tonight.......I don't wanna hear no **** about it either.

So its 91.1 cc's on the 661 vs 91.6 on the 660, or is my math off?

 

[HuskStihl]

Hmmmm, spring AV.....a more over square cylinder..... That usually means better RPM's/hp at the expense of torque.....I can't put my finger on it, but it's reminding me of something.....

 

[mdavlee]

Hmmmm, spring AV.....a more over square cylinder..... That usually means better RPM's/hp at the expense of torque.....I can't put my finger on it, but it's reminding me of something.....

Sounds like a husky

 

[nmurph]

Sounds like a husky

You didn't just go there??????

 

[mdavlee]

You didn't just go there??????

I did. I wondered why they did it and not keep the stroke the same to be at 94cc like the 395. It doesn't seem to need any more cc to whip the snot out of a 390 as is

 

[HuskStihl]

You didn't just go there??????

Oh no he dint.... Two snaps up!

 

[shootingarts]

It should make it handle poor fuel a little better......but that's all I can see.

The engineers that build these things are smart........real smart. They make me slow down and really look things over when I see a big change like this.

Randy,

No rush at all but if and when you get time I'd appreciate an explanation of the shorter stroke handling poor fuel better in a two cycle, I'm trying very hard to understand these little beasts. The reasons for going to a longer stroke compared to the bore in cars and light trucks was to deal with pollution issues and the reductions of lead in gas way back when. Before sophisticated computers in the early seventies longer stroke gave the engines more effective dwell time and more room for error or inconsistent conditions. Just as a general statement, the more time something has to happen in a combustion cycle the less critical the timing of everything happening is.

Were this a four stroke engine I would think that the computerized ignition and carb control allowed a more oversquare engine rather than the shorter stroke being a benefit to aid consumption of inferior fuel. No accident that two of my favorite engines, the 289 Ford and 302 Chevy, couldn't be produced in the seventies. The 289 Ford was the most oversquare factory V-8 in any of my manuals and the 302 Chevy was next behind it.

The short stroke big bore four cycles were screamers but they were inefficient and dirty, I loved them! When I was going to run an open wheel class limited to 355CI I was putting a 302 crank in a smallblock 400. I was also planning to turn about a thousand RPM tighter than most of the "standard" 355's. The 661 should be able to turn a good bit tighter than the 660 if the controls let it. That means that it should love to be modded!!

Hu

 

[Officer's Match]

^ Agree, DZ's and MO's were just nasty. I had a '68 Z-28 with a 40 over blue printed 302 with an aluminum flywheel and 456's that was very feared in my town.

 

[procarbine2k1]

Sounds like a husky

Blasphemy!

 

[mdavlee]

Blasphemy!

I guess if they couldn't beat it they would copy it and paint in white and orange

opcorn:opcorn:opcorn:

 

[HuskStihl]

I was funnin' with my earlier post, but that saw (at least on paper) could easily feel like a really strong (and really expensive) 390. 300 bucks less gets u a new ported 2188 from some other TN builder. Just sayin'

 

[Mastermind]

Hu, From what I've studied on combustion chamber design, dwell time, and detonation.....it appears that the guys at Stihl have been reading the same stuff.

They have designed the quench area with a wide, flat band.....quite a lot wider than the 660. That in itself helps with detonation resistance. Then the shorter stroke allow dwell time to be shorter......again, that should make the engine more tolerant of detonation.......which is why I said it should handle poor fuel better.