What's up with this exhaust port?

[ErnieG]

I got this saw as a parts saw and have no idea what was done to this exhaust port ... anyone ever see this before ?
It appears to have been ran as it is but not by me .
It's a 2186 by the way
Ernie

 

[Maintenance supervisor]

I got this saw as a parts saw and have no idea what was done to this exhaust port ... anyone ever see this before ?
It appears to have been ran as it is but not by me .
It's a 2186 by the way
Ernie
View attachment 1167108

It's a step that's supposed to increase the flow of the exhaust without making it a bigger hole, it does work .

 

[huskihl]

Does the piston go above the hole at top dead center?

 

[ErnieG]

Does the piston go above the hole at top dead center?

No it doesn't

Ernie

 

[thompsoncustom]

It's a step that's supposed to increase the flow of the exhaust without making it a bigger hole, it does work .

how does it work? since 90% of the pressure is bleed off when the port cracks open I don't see how having a cutout in the bottom would do anything.

 

[huskihl]

Some west coast port guys will do that to intentionally free port the bottom of the exhaust skirt. It may or may not help pressurize the case in an attempt to push more charge through the transfers. The notch would actually need to be below the skirt at top dead center though. Looks like someone copied it without really understanding what it was and how it actually worked. Same as the lungs or Mickey Mouse ears in the intake

 

[RedneckChainsawRepair]

Yep but not the step part.

Was a west coast thing at one time. Some folks tried it this way too in mid west.

IMO not needed.

394 came from Oregon a local brought in.