Aftermarket MS660 Performance

[MustangMike]

4,500 RPMs is way different than 14,000, but the point about diminishing returns I'm sure is valid.

 

[brshephard]

I found this link, about compression and more heat generated, as well as knocking, not really sure if holds up to chainsaws. But it’s worth thinking /looking into. Maybe another reason why some chainsaws grenade

http://www.bridgestonemotorcycle.com/documents/higher_compression6.pdf

Good read.
I've learned from folks on here that these saws have pretty low compression ratios, like less than 10:1.
They also have pretty low specific output.
An MS660 is 92cc/8hp = 8.7cc to make 1 hp

My stock Skidoo snowmobile is 160hp/800cc = only 5cc to make 1 hp

That's how guys can get away with 200+ even in production falling saws.

Is 200+ better though? I'm not sure. Thats why I joined here, to try and learn the tricky design stuff.

 

[MustangMike]

But, power to weight is were the chainsaw shines, and why is stays 2 cycle!

 

[brshephard]

Braaap!

 

[brshephard]

New jug came in today.
What numbers should I try?
Its at 97/128/82 stock
Here's some pictures:

 

[brshephard]

And the transfers:


The combustion chamber looks big compared to the farmertec

 

[Wonkydonkey]

I don’t know if you got a squish reading, but it’s a starting point weather you use any type of gasket, that’s if you don’t have a lathe. I can’t remember if said you did or not.

 

[MustangMike]

Tough #s!!!

 

[Fruecrue]

This one is 101/119/83
.018” squish
.040” pop up
195 psi compression.

 

[brshephard]

Nice job! Chain looks money too.
Did you find more torque going with a shorter blowdown?

 

[Fruecrue]

I didn’t mess around with blowdown so I can’t comment on any difference.
Pop up, timing, and port width were the big gains.

 

[brshephard]

I see, nice work.
I think I'm gonna go 101 as well.