I know the theory has merit.
Keeping the the piston, head, and cylinder cooler by using a thermal barrier and shoving the heat out of the pipe should have several benefits.
The pipe will get hotter as more of the heat is shoved out the cylinder.
But that will improve scavenging as you are changing the wave speed in the pipe.
You should also keep the engine cooler longer which all by itself keeps that fresh early power longer.
That is the hoopla, but does it really work?
Let's take a walk down memory lane...
Remember when windowing the KX500 piston was the big rage?
Why?
Because on the land speed bike, the piston crown was getting very hot and needed to be cooled.
Adding the window gained 3HP on the dyno so of course everyone wanted it.
It wouldn't really help most stock bikes or trail riders but Supermoto or desert guys could use it.
Due to the current round of engine mods I'm experimenting with I could use the extra cooling but, I can't use a window...
So, let's try it and see what we get
Here is a couple of pics for your enjoyment..
Jason Meyer CR500 Expert. I know, I know, it's a valve slinger but some of the principals are the same..
Alex Ward KX500 Guru