I had a conversation with mike on this a couple weeks ago yes the kyosho spur does fit with no mods but depending on what kv your motor you may need a extremly small pinion. my motor is a 2000kv I would need a 11t pinion maximum the problem is when there so small the mod 1 pitch gets thown off a little. He did suggest a 51t spur from a HB lightning then you could go with a slightly bigger pinion. here is a tidbit of information he filled me in on is the x1-crt is geared the same as a buggy hence the reason for that large spur.