What kind of options do I have for my brothers 90 in boring it over. I have been looking for awhile and can't find any kits online or anything for it and I was wondering if mayber I can use a CRF100 bore kit in place of a 90. I am lost and just looking for some answers. My brother wants to get into racing and he doesn't have the smarts for it but i do.
Any help will be great and I am new on here and new to the racing scene but I have been riding for a few years.