I guess if I was to try this, I would use a Leopard carb, HL-334AB, although I would find it rather awkward reaching back to fiddle with the needles to tune on the fly.
In my opinion, I can’t see any thing wrong with the Mikuni TM28 carb. Once you get the jetting down for the tracks you visit, it’s just a matter of watching the air quality and adjust accordingly. Of the 4 tracks I go to, I only have to change the jetting for 1 track, it is 1,500 feet higher in elevation, one step down on the main jet and I’m on my way.
Gary
#55 Honda CR80