Yes, you can replace just the inner ,but i don't think you can buy the inner cable. I think the main cause of cable failure is lack of lubricant, you will get warning signs, bouncing speedo, noise from the cable to name two. Chain lube is an easy way to lube the cable. When I bought one for my Yamaha XV250, I tried to get the inner cable, but the genuine one was only about $20, complete, inner and outer.