Cylinder Stuff

Porting Thoughts
This page is under construction: Public Notes (Culled)

There is no one right way. I have seen them cut in all KINDS of configurations. Here are a few guiding principles. The ROOF of the third port needs to POINT UP to the spark plug. There are are a few different ways to look at timing it. You can either time the third port 1.5 -2 degree BEFORE the transfers open, at the same time, or AFTER the transfers open. Timing the 3rd port BEFORE the transfers is good for low-end torque. Timing the 3rd port AFTER the transfers is good for high rpm HP. Timing the 3rd port at exactly the same time as the transfers is a balance between the two.

This port has to get fed by crankcase gasses when the piston is at BTC, so there has to be some connection between the 3rd port, and the crankcase, when the piston is down there. This either involves cutting out that trench down from the intake port, into the skirt of the cylinder, thereby connecting the intake port with the crankcase at all times. Or, it involves cutting a hole in the piston that lines up with the intake port when the piston is at BTC, again, to facilitate a connection between the crankcase and the intake port (and thus the 3rd port) at BTC.

60 120
21 16

Exhaust: Somewhere around 120 degrees upwards towards TDC and approx. 21mm wide. /// Intake: 60 degrees on the down towards BDC and approx. 16mm wide. — Make a note and save those numbers as a base.