Hi Juan

I don't believe there are issues within supermoto re v-twins (i.e Aprilia RXV450/550 v-twin) but there is potentially an issue with motocross.

AMA (american) MX regs has previousley had a singles only policy but Aprilia are trying hard to get this changed, a lot of countries follow either the AMA or the FIM rules pretty closely.

Not sure what set of rules various countries follow, however, unless your at national level i can't see it being too much of an issue.....

Mark