hey, 1adam12 posted teh same question about his 85900 in the vintage forum. here was the reply i gave him
Its not all that tough but it does take time and patience. Stock swingarm might be wide enough to take up to a 180(as its been done on the gpz) but I would reccomend a swingarm swap if you want to go that wide.
Do you just want to change wheels or you want to do the forks as well? If you do forks its only a matter of a custom steering stem that will press into whatever forks you are going to use. And the brakes and everything off of that bike. If you just want to do the wheel its a different story. Because you have to make sure your calipers are in the proper place for whatever rotors you use. make sure the speedo drive gear isnt too wide and will offset your rim. Older rotors tend to be thicker then newer ones as well. I went from a floating caliper setup to a floating rotor setup.
for the rear the biggest thing is to make sure your chain and sprockets all line up. You may need to get a custom offset sprocket. I dont remember if your bike runs a 630 chain or not but a 530 conversion will be needed to run modern rear sprockets. Also keep in mind if clearance is a problem that 530 oring chains are wider then 530 roller chains. when ever mm counts. The rear wheel isnt as important to get centered as the front, alot of newer bike have the rear wheel offset factory. I like to have it centered but thats just me. If you end up changing the swingarm with the wheel you wont usually run into problem getting the rear caliper to work. if you just do the wheel again you have the same problem as the front with rotor diameter/location and thickness. I know my gpz caliper and gsxr caliper were similar but the gsxr rode below the swingarm and was much thicker(on the axle). If you swap the rear arm you have to make sure that the pivot width and diameter is close to that of your bike. I lucked out with the gsxr arm being a hair shorter but the pivot was a larger diam so i had to machine a few spots, but the inner race from the gpz arm slid right in. Then the problem of the rear wheel goes away and you need to focus on suspension linkage which can be tricky.
There are alot of things to think about before starting something like this. Really the best thing is mockups. Unfortunately when i did my swap I started in the middle of summer which i regreted loosing good riding time. If you decided to swap more then just wheels i would start with the front end because it is easier and then you can put the rear how ever you want to get the chassis attitude you are looking for.
If you have specific parts you are using or dimensions I can try to give you a hand. Right now a friend and I are getting a cnc business off the ground so in a few months I might be able to do some custom parts if you end up needing them, ie caliper mounts, steering stem, etc.
since i dont have a 900 this was all generic info but usually applies
Sounds like alot of work and I already have about 4-6 weeks ahead of me with the work I have now on the bike.
So I am thinking I will repaint my spokes and re-polish the lips and they should be ok.
But I think I will just raise the rear of the bike a lil to give it more of a moderm look.
I think I can make a bracket where the shock comes into the swingarm to adjust the leverage there.
I still need to buy a cycle jack before I can go any further on the bike itself.
I was thinking in the meantime I might just go ahead and polish my head cover, the side covers on the trans, and some other misc parts.
Might as well since I cant move onto the wheels until I get a jack.
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