when the size of your main jet exceed 190(more or less) be sure, that carb wont respond on a 4 stroke engine nor designed to do so

all 4 stroke high performance carb from mikuni (as i use TM 33 pumper on my 200CC!!) use acc pump and flat side pistons

a guy fits the mikuni TM 40 by cutting the frame and rewelding it on the same shinery here ... the performance was great