To be honest im not sure on the liter bikes, id say go ahead and stick with a quad/dirtbike mastercylinder because they are smaller, my zx636 had a pretty big mastercylinder on it. I bought an 08 yfz450 mastercylinder off of yfzcentral and put it on with my stock lines and calipers and it made a huge difference, so since the yfz front calipers bolt right one..I bought a pair for 50$ shipped and put them on, and it did make a difference, but what made the biggest change was the mc. And I agree with broncbob, the trx450 mc should be equally as good!
heres a post I did over on e2s!
http://forums.everything2stroke.com/showthread.php?t=27924