You don't have to disassemble the whole chassis, but you do have to pull the wheels from one side to unscrew and pull out the brush holder. Having done that, it is just four screws to take the side frame off and you can do a thorough inside cleaning.
To take the wheels off, you need something that will hold the bottom side of the frame while you use a big hammer and a nail set to drive the axle out of the wheel on the top - slowly, carefully, Be patient and it will come out.
I don't know what advice to give on resetting the wheels other than having an old vice like mine. IT's an 80 year old vice (from y father's workshop) that has 2.5" between the jaws and is well squared. Since the axles normally end at the wheel surface, it's easy to get the gauge right. Don't know what modern tools will do the job.
ML
