Looking at the angle of entry of the intake charge from the transfer ports of a Grubee engine it is easy to see that too much of that charge will just go out the exhaust port instead of staying in the cylinder and contributing to engine power. With a Dremel or Black&Decker rotary tool and some JBWeld you can fix the transfers so you pollute less and get much more engine power. Please see the section on my site about this by clicking on my signature link.