all the xs motors are pretty much the same. pre 79 has a points ignition, 80 and later is CDI. the carbs on a pre 79 are MUCH better though, and i can build an electronic ignition for an XS for under $20 from scratch. if you look hard enough, you can find a decent XS motor for next to nothing. i got mine free actually. i put a post on craigslist a while back stating i was looking for an XS frame and/or motor, and i had a guy GIVE me the motor that's in my chop. i even tried to give him some money. he wouldn't take it. XS's were made from around 72 to 83, and they made a friggin million of them, so if you look in the right places, they can be had for cheap. hell, i had a guy come into the shop the other day telling me he GAVE AWAY a pair of complete xs's, with titles. i was PISSED, to say the least. i would have gave him $100 a piece for them, chopped them up, and made a small fortune on selling them!