Too much compression?

[jmssaws]

My 66 makes 230 with the squish over 030.
There's a big difference in squish when the chamber is cut some or a bunch.
020 can be 200 or 250,depends on the chamber.

 

[Cj genever]

Yeah, the 262 cylinder had a decent crown to it. I'm surprised it is this high without popup

 

[jmssaws]

U can't use a popup it makes far to much power! Everybody knows this.

Honestly if your exhaust doesn't need lowered a popup should do just fine.
I don't build saws with them anymore only because of replacing the piston.
My 372 has had a popup in it for years and I've not felt the need to replace it.

Everyone that has built saws for a long time started with pop-ups, a 90cc stihl is what changed all of it.

 

[drf255]

To the OP,

If that's compression after running the saw and you want to reduce it (I wouldn't), you can chamfer the SB to chamber interface. It won't affect port geometry or the benefits of a large wide tight squish.

A little goes a long way though.

My Stihl 036 runs at 215 psi and hasn't had a single issue on any fuel.