Maybe you could fit a Suzuki L650 Savage air cooled engine........you could fit a Triumph 2,300 cc triple....or a small block Chevy....you could buy a BMW F650 with full warranty....you could move to a country that sells bigger bikes....

Hmmmm...you're up awfully late. And here I have wasted a day thinking about this stupid subject when I don't actually own a CBR!!!

I have no idea why Goodspeed list different bore-up kits for the same engine, I can also see differences in CBR-125R and Honda Sonic 125 which is the identical engine. It is not the first time I deal with Goodspeed, and I can ensure you that if you call you get the same answer I say. The engines of all 3 motorcycles (CBR-125, Sonic 125 and CBR-150) is the same. (For the CBR-150 the only difference is the cylinder, piston and head assembly)

For people thinking to bolt-on a CRF-250 cylinder or CBF-250 cylinder, I would say not get you hopes up and not talk about it in a motorcycle garage, you will surely become the laugh of the day