I'm not sure if it applies to mini bikes but another thing I wanted for my Briggs motors was a compression release, so about 30 years ago I figured out how to make one. It does the same thing a Whizzer motor compression release does. That is it lifts the exhaust valve off the seat slightly. I've had dirt bikes with a release in the head of my 2 strokes but it spit fuel/oil all over the bike, very messy. I take the governor out of my Briggs motors and use the shaft bushing to install the lifting lever. A cable attaches to it and is activated with a hand lever on the bars. Very simple and fairly easy to make. The motors start easier and I sometimes use it as a brake in a slippery corner where I don't want to lose traction.
