It’s not the port timing, or squish or fuel itself.
The MT on this particular saw can’t fatten up the tune enough to control rpm on a saw that gets too hot. Two reasons why:
Fuel mix too thick to flow enough
Saw heat above capacity that MT is programmed/designed to handle.
So if saw gets too hot from too much compression regardless of squish, the system tries to fatten up the tune. If the fuel mix is too thick of a viscosity, it can’t flow enough fuel to rectify the situation regardless of how fat the MT tries to make the tune. Then all sorts of bad stuff starts to happen in the MT computer.
So in the right situations, compression, ambient temp and fuel mix won’t affect anything. But take too much out of the squish band and make the chamber too small and There’s a problem Houston.
Saw run around 185psi stock. Cutting the band for a nice flat tighter squish is likely all that’s needed. Pull 50 out of the chamber and keep squish at 15 and the saw likely has 275 psi and gets too damn hot.
Bigger MT saws have bigger jets, needles, seats, etc-So they likely aren’t affected by the issue as often.
I’d venture to say that saws that don’t have the issue have either better cooling systems, lower factory compression or a fuel system that’s large enough to flow more.
