Another chainsaw dyno...

[rogue60]

Interesting, I considered the term 'bogging' as when the engine quickly falls off the torque curve, the revs drop and the centrifugal clutch slips. You can often fix that problem with a richer jetting in the low speed circuit to increase the low speed torque to keep the revs up.

In your definition, it was a clutch that slipped at lower revs. In other words, you could keep leaning on it, the engine had the torque, but the clutch would begin to slip.

EDIT: I wonder if the later clutch with the lighter shoes and stronger springs was an EPA idea. That is, it made the user keep the revs up so there was less emissions out the exhaust port at very low revs.

Yes it would bog and clutch slip it was only happy if keeped in the upper rpm range bit hard to do cutting hard hardwood 3/8 chain was better it didn't load the saw as bad but I don't like 3/8 That's why I run 90cc to pull .404 and they used to the old Aussie 660 was fine running same bar chain.
I thought at the time it must of been that Stihl was reading chainsaw forums and tried making a cookie cutter lol
Wasn't a one off my dad has two 661 he goes off he's nut about the bogging and clutch slip. This is with stock 661 no mods.

 

[Terry Syd]

I'm like you, I like an engine with heaps of low end torque so that I can keep leaning on it and then notice that it isn't cutting because the clutch has started slipping, usually below 6,000 RPM.

Oh, that's right, you also cut Ozzie hardwood - LOL.

 

[rogue60]

I'm like you, I like an engine with heaps of low end torque so that I can keep leaning on it and then notice that it isn't cutting because the clutch has started slipping, usually below 6,000 RPM.

Oh, that's right, you also cut Ozzie hardwood - LOL.

Wasn't that I'd lean on it just normal cutting in the meat of the power but the 661 at that working rpm is right on a knife edge of bog or no bog the heavy clutch made mine a different saw for lack of better words gave it some balls...

 

[Bigmac]

Wasn't that I'd lean on it just normal cutting in the meat of the power but the 661 at that working rpm is right on a knife edge of bog or no bog the heavy clutch made mine a different saw for lack of better words gave it some balls...

I had the same issue with my stock 661, I did a bgd muffler mod,(big single outlet) and maxflow, then a timing advance, completed different saw! No bogging at all, and I can dog it in pretty hard now and it won’t bog down, I run 3/8 8-pin 36” I am still thinking about trying your 660 clutch mod. The more the marrier! Before the mods, I thought the 661 was a turd!

 

[rogue60]

I had the same issue with my stock 661, I did a bgd muffler mod,(big single outlet) and maxflow, then a timing advance, completed different saw! No bogging at all, and I can dog it in pretty hard now and it won’t bog down, I run 3/8 8-pin 36” I am still thinking about trying your 660 clutch mod. The more the marrier! Before the mods, I thought the 661 was a turd!

With your mods and the clutch mods would be a grunty saw.
Only problem finding a new old style heavy 660 clutch to use the shoes and springs from.
The one I used was out of my old part saws.
The part numbers are superseded order a ms660 clutch and Stihl sends you this light rubbish lol yes it has the same light shoes as 661 but springs are still 660
The last of the ms660 you could buy here had this light clutch in it.
You guy's might have a better dealer than me and can track one down am sure they would be still out there? My dealer just says that's all you can get now.

 

[mdavlee]

The only other saws I’d like to see are ported 385/390. I’ll send a stocker in after next weekend when I’m home for a few days. It seems to be pretty strong and I’ve not even opened the muffler up like I used to. I would like to see Lee’s 60mm 166 on there eventually.

 

[qurotro]

With your mods and the clutch mods would be a grunty saw.
Only problem finding a new old style heavy 660 clutch to use the shoes and springs from.
The one I used was out of my old part saws.
The part numbers are superseded order a ms660 clutch and Stihl sends you this light rubbish lol yes it has the same light shoes as 661 but springs are still 660
The last of the ms660 you could buy here had this light clutch in it.
You guy's might have a better dealer than me and can track one down am sure they would be still out there? My dealer just says that's all you can get now.
View attachment 247639

Well the chinese clutchs are the heavy shoe one.. Maybe just use its shoes? The spindle might crack as I read.

 

[qurotro]

The 660 clutch assy in the Stihl system now shows 1144 clutch shoes in the list which means... They are all 661 shoes..

 

[Terry Syd]

Thread those holes in the shoes and screw in some bronze/brass bolts. You can actually make them have more mass than the original 660 shoes.

 

[Red97]

Thread those holes in the shoes and thread in some bronze/brass bolts. You can actually make them have more mass than the original 660 shoes.

Some heavy metal Mallory bolts

 

[Moparmyway]

Some heavy metal Mallory bolts

I’ve seen slugs, blocks, even darts made with heavy metal, got a link for threaded bolts ?

 

[dustinwilt68]

I would be interested in seeing what @Redbull661 Zeus saw makes for power, that saw stood out to me when I got to try it, he had another 661 also, booth were great runners.

 

[Red97]

I’ve seen slugs, blocks, even darts made with heavy metal, got a link for threaded bolts ?

Prolly have to turn them on a lathe.

Might be able to run a die down a rod.

 

[huskyboy]

I would be interested in seeing what @Redbull661 Zeus saw makes for power, that saw stood out to me when I got to try it, he had another 661 also, booth were great runners.

I would be fascinated to see the torque curve side by side on a graph with John’s 661 stroker to see if there is a difference across the curve vs a normal stroke ported 661. The stroker was no joke when I ran it.

 

[RI Chevy]

There's another one in CNY...
661 Showdown...

 

[dustinwilt68]

Would be interesting to see the difference for sure Mason, is all the extra work of the stroker worth it? Also curious and I am asking because I have never seen or ran it, is the stroker a work saw or race saw?

 

[Red97]

There's another one in CNY...
661 Showdown...

Send em Jeff...

 

[huskyboy]

Would be interesting to see the difference for sure Mason, is all the extra work of the stroker worth it? Also curious and I am asking because I have never seen or ran it, is the stroker a work saw or race saw?

It looked like a “worksaw” Dustin but I’m not sure. You would have to ask John about it. I would guess the more oversquare saw would have a max torque peak that is similar to the stroker... but the stroker would probably have a flatter curve over the rev range is my guess. But who knows I could be wrong lol. 3mm is a lot of stroke difference though.

 

[RI Chevy]

Send em Jeff...

I don't have one...lol
But if I did, I'd send it...

 

[dustinwilt68]

For sure, I have heard it is an amazing saw, lot of thought in that build for sure!