The Bimotas had 3 problems, the first being they were a Bimota! The injection was the second, it worked most of the time but was abit hit and miss with the throttle responce, the third was they had some probs with the barrels, this was sorted and once coupled with a set of carbs the bikes werent too bad, they did sell some "SP's and Corsa's" like this but not many. All the ones we sold ended up going back and everyone got a 6 or a 6R for free, i can't remember which. They never made much power though.
As for 28 carbs, Ive not seen a set myself but most flat slide type carbs lend them self to being bored alittle so im sure there is some scope in there. Try talking to some on the MX guys as 125 lads are always having carbs bored.
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If I have to take the carbs off once more...