Building off of the information in this post Port Timing & Duration, I've created a spreadsheet for DIYers to mess around with engine building.
The blue numbers are the ones to mess about with. and you'll find how adding a spacer, changing stroke, rod length, bore affect your port timing on the three stock yamaha cylinders:61x, 62t,64x.
The blue numbers are the ones to mess about with. and you'll find how adding a spacer, changing stroke, rod length, bore affect your port timing on the three stock yamaha cylinders:61x, 62t,64x.