ok first of all, numbers arent everything. I will tell you many numbers that you can cut the intake and exhaust durations to, but honestly thats half the battle. 65% of the bore on exhaust width is a good safe number, but still they can go more. Depending on the shape, again numbers arent everything! Trust me, ive been porting for almost 5 years now, still doesnt even amount to the dirt under your nails compared to a "builder" but ive done many sets and seen many outcomes. Ill tell you some numbers to start with but thats all they really are; compression, pipes, timing, carbs,rider weight, and lenght of track are just a few things that all play a role. ooohhhh and maybe the ummmm.....shapes and angles of the ports might have a role in this
Im not saying this will work best for what your setup is your riding style but they are numbers, thats all you asked for; but remember they are just numbers
199/127
stick with the 65% of the bore for exhaust width to be safe.
the rest is up to you, also dont forget that higher durations doesnt always work best for every application..it is your decision to cut the cylinder, i just provided a couple simple numbers i hold no responsibility here. GOOD LUCK.