Gents,
I have a spare set of stock RD 350 cylinders, still at stock bore, that I am considering having bored to +.25 or +.50 mm, as well as converting them to RD400 head gaskets and fitting dowels to locate heads.
Is it worthwhile having a local 2 stroke shop clean up the transfer ports first. Just removing any steps and casting flaws in the upper part of the transfer ducts and the ports. And maybe cutting the boost ports a bit deeper as well. No plans for more exhaust port duration, however.
If you have an air compressor you could buy a die grinder at Harbor Freight and clean up the ports yourself.
if you local shop has a porting tool, then yeah its not bad idea, the roofs of those ports shaped and cleaned up can def help.
I do have straight die grinder, a Dremel etc, but no right angle handpiece. And since those are pretty expensive, I am looking at having this done by a somewhat local shop. I can easily deal with intake and exhaust ports myself, but do not intend to change timing, maybe just improve the exhaust port finish to slow down carbon buildup.
Sand blast
Reducing and removing the ledge is basically the first thing you do. Matching the sleeve at the divider is common. I see a lot of knife edged cylinders there. Knife edging is easy but it's old school. Nice rounded and blended ports are preferred. Then clean up and set port timing.