Luggage Storage in JR Stations

Hello all,

Do all JR stations have luggage storage - large enough for large suitcases? Specifically - I'm staying in Kyoto for two days and then plan to stay at a Ryokan in Kameoka. I would like to check out of my Kyoto Ryokan and travel via JR with my luggage to Arashiyama (leave my luggage at the station) spend the day in Arashiyama, pick up my luggage and continue west via JT to Kameoka.

I would also like to do the same thing in Okayama (and leave my luggage in the station for the day)