Gday there, New to the forum and this is my first post in an attempt to be helpful. A good way to test for wear is to kick the bike up onto the centrestand and get the rear wheel up, grab the swingarm with both hands and try to move it side to side. If there is ANY movement whatsoever the bushings need replacing, if no movement then they are good to go. If you do replace with the factory specs nylon-plastic ones be vehwy vehwy gentle as they will split and crack and do all sorts if you hammer them in too hard. I would suggest getting the steel ones and making sure you grease it like theres no tomorrow. Worn bushings are the sneakiest of handling killing ailments, mine felt like a new bike when i replaced them on my cb650z.