If I want to put rims on that have 3/4 axles? Do I just change them to 25mm bearing which I have now? what do I need to do to the wheels if anything?

 

You change the wheel bearings in the wheels to the proper size. You may also need a sleeve to go in between the bearing that is also the proper size, 25mm ? Or you can put new 3/4" bearings in the wheels and buy a new 3/4" axles.

 

You may need new wheel spacers and also to ensure that the brake rotor(s) line up with the brake calipers. If you indicate a specific wheel for a specific motorcycle, I am sure someone on this forum will give you the specific answers you need.

 

Like the previous poster mentioned you need to be specific on they type of wheel. It is my understanding in order to use 1" or 25mm bearings in a OEM wheel the center needs to be bored to accept the center spacer. Depending on the wheel, most 3/4 axle wheels are narrower than those with the 25mm bearings so I am not sure why you would want to go with a narrower wheel?
CB

 

Most hubs that use a 3/4" bearing will have to have the center bored to accept the larger center bearing spacer for the 25mm bearings and axle. The O.D. of the bearings is the same size so the 25mm bearing itself will fit into the same hole that the 3/4" bearing was in. Another issue is that the 25mm bearing is a thinner bearing so if you use it in a hub that originally had a 3/4" or 1" bearing in it you will have to have custom cut outside spacers because the 25mm bearing will set deeper into the hub. You can not install new 3/4" bearings and buy a 3/4" axle because your lowers nor your swingarm will work with a 3/4" axle since they were designed for a 25mm axle.