Disklavier

Hi, I am new to the group. I would like to know how I can clean the solenoids and their housings in my disklavier. The solenoids in the middle section of the piano are getting stuck. When I took them out of the piano and moved the plungers in and out of the shaft i could feel that they are pysically getting stuck. Some are easy and free in their housings moving correctly while others are not moving corectly.
What could I use to clean them?? I have tried to replace them with the correct part no through Yamaha but when the parts arrived they were different in diameter and would not fit in their shafts. There must be someone out there that would know how to perform this maitenence on the dkv. This must be a problem for other owners. I would appreciate all the help I can get. this problem is driving me mad!!!

Thanks everyone in advance

Wayne