Im trying to buy a engine case on **** for my nephew, I think his bike is a 99 rm 125. How can I tell for sure. The frame # is js1rf15c9x2100637 and engine #f114-152830. I need the right side case and can buy both sides, matched pair for 125.00 buy it now price, Is that a deal??tHANKS FOR ANY HELP.