I have a 91 XR250R and was wondering how much MORE power the 280 kit gives it and what is involved in doing it? Where can I get it? How much does it cost?Do I have to send my engine away? Does the 280 kit affect reliability any? Does it give the powerband a little hit? Does it hurt Bottom end performance? I know its alot of questions, Matt
Big bore kits with no other mods tend to improve bottom end performance and don't impact reliability if they are done correctly.
Check www.powroll.com/honda_xr_250r_86_94.htm for the answers to some of your other questions (price, etc. ) or you can call Powroll and ask for Pam. She can answer all your questions on the 280 kits. Pam is a regular contributor to DRN.
i put a 280 kit in my 98 xr from summers racing and was very happy. have the cylinder bored by someone who is familiar with 4 stroke motorcycles. the kit is basically a 77mm weisco piston and gaskets, they will also help with jetting. this is an inexpensive mod if you are capable of doing the labor. don't expect a firebreather, just a little more thru out the powerband.