YZ 490 Porting Question

[Joe in Florida]

I have an 83' YZ 490 that I race on a Go Kart. We run on an 1/8 mile and a 1/4 mile clay oval track. I have two different cylinders that I can change when we are running at one or the other track.
The question that I have is, to get more torque on the bottom, do both Transfer and exhaust ports need to be lower or just lower the exhaust port? I have .020 before the piston is flush with the top of the cylinder. If I machined the .020 off of the bottom of the cylinder, what would I need to do to which ports working towards getting more off the corner?

I would appreciate any info that will help me get off the corners better.

 

[ZeCatfish]

Lowering the ports will lower the powerband, not sure about the cross over verses the exhaust.

 

[Joe in Florida]

Thanks for the info,
I cut the .020 off the base of the cylinder, with the exhaust port
opening @ 88 deg after TDC and a squish band clearence of .053 the combination of the two should help. Also switching from 100 oct to 114 fuel.
Thanks again,
Joe