Usually the putty type ramp in the crank is done after the crank is drilled a little deeper into the front side of the crank to lighten it up more, the putty stuff fills that hole in and "helps" the flow a bit. If you do some searches online for anything relating to a 2-stroke engine (dirtbike, snowmobile, etc...) or the exhaust system for a 2-stroke engine you will be able to learn more than any info you find that is from a r/c website.