How To Fix The MS661 Bog

[Mastermind]

Never been banned. Never had one of my threads locked. But bruised vaginas? Yeah. I've done that

Please sir. No pics.

 

[jacob j.]

Even just idleing the ms660 in ones hand, you realise its a saw from a past generation. Is there much wieght difference between pistons in the 661 compared too 660? Arhhh saw details......its all in the details. I think guys like G.Bell advocated a chamfered piston skirt for better lubrication?

I've seen something about that. I've also seen documentation of an exhaust gas dissipation groove mentioned on the bike forums. I've seen a couple of saw builders run such a port and they called it a "rafter port."

 

[huskihl]

Please sir. No pics.

Awe heck no. That was waaaay before digital cameras lol

 

[Mastermind]

I've seen something about that. I've also seen documentation of an exhaust gas dissipation groove mentioned on the bike forums. I've seen a couple of saw builders run such a port and they called it a "rafter port."

Partner P70 has that type of exhaust port. I think they called it a Tee port.

 

[DSS]

You can reduce vibration in modern Stihls by making the piston lighter.

Like out of a tunafish can?

 

[Mastermind]

Like out of a tunafish can?

 

[Adirondackstihl]

Partner P70 has that type of exhaust port. I think they called it a Tee port.

Pics?

 

[Mastermind]

I probably have some.....but I'm not sure if I can find them. I ported a P70 when I first started building saws.

I'm sure I took pics......but I've gone thru a lot of hard drives since then.

 

[CR888]

I've seen something about that. I've also seen documentation of an exhaust gas dissipation groove mentioned on the bike forums. I've seen a couple of saw builders run such a port and they called it a "rafter port."

Before today, I had never seen/ heard of such a 'rafter port' ....that's why I always enjoy & usually learn something when reading a jj post, especially when ya tell us what mods guys were doing to saws before I was born.lol So what is the principle function behind the rafter port? Your probably sleeping atm so its given me something to google.

 

[Mastermind]

The slot above the exhaust port bleeds off compression at low speeds......like when cranking. Once decomp valves became common, they were not used any longer.

 

[awol]

Pics?

Not a P70, but here is one similar, a P100.

 

[Mastermind]

Thanks Alan.

 

[czar800]

Before today, I had never seen/ heard of such a 'rafter port' ....that's why I always enjoy & usually learn something when reading a jj post, especially when ya tell us what mods guys were doing to saws before I was born.lol So what is the principle function behind the rafter port? Your probably sleeping atm so its given me something to google.

Well said!

 

[angelo c]

Not a P70, but here is one similar, a P100.
View attachment 6874

I say that's an AM Circlip that got busted in the cyl....nasty looking.....

J/K...

 

[Moparmyway]

Here is a second way of getting rid of any problems

 

[Moparmyway]

No running problems now !!
Stock untouched from Redbull, 404 RS in hard oak

 

[stihlman441]

I changed to the new coil/controller it improved the top end but still has the un even idle after the cut and has never had the bog issue

 

[TJ the Chainsaw Mechanic]

Thanks for posting a solution! Good stuff to know as alot of guys have purchased 661's in my area.

 

[Moparmyway]

I changed to the new coil/controller it improved the top end but still has the un even idle after the cut and has never had the bog issue

Even without the mtronics, my little snort after the cut is still there. Its way less noticeable, but allways there

 

[VinceGU05]

If it is running well.......I wouldn't worry.

Here's what I've noticed on the ones that need more fuel. You will come off of a big cut and the saw will hurt around for idle and sound "off"......

my 084 does that:/