honda make a 250cc v-twin... they had a vt250f back in the 80's, and then they had a vt250/spada in the late 80's/early 90's... then recently they brought out the VTR250 which is pretty similar to the spada motor
the spada motor is probably the pick tho, as it made more HP (about 36) and had 6 gears whre the VTR250 was detuned a bit (32 hp) and only has 5 gears. the spada was a little more revvy.. with a pipe they are pretty fun. both motors can tend to go thru cam chains + tensioners... they make a lotta noise when they go but its not that big a job, unless you ignore the 'clack clack clack' sound for a few months
shouldnt be hard to get a motor cheap because they are a very common grey import