Topic: Swapping fork caps on a CB650C

[NateTheBookie]

Hey all, I just got some progressive springs and tapered rollers for my front end, I'm going to start monkeying with them soon. I was looking at the instructions for the progressive springs and they recommend starting with no air assist.  I'm currently running '80 650 Custom Forks and triple trees on my '82 nighthawk (I like the handlebar setup better, and the forks from my parts bike were in better shape than the nighthawk forks). I'm thinking about dropping the fron end my .5-1" or so, and I would like to simplify my head setup as much as possible, so I was thinking about removing the air assist system altogether.

I could just plug the holes on the stock 650C caps, but I would rather find some standard airless caps that fit these forks. Does anyone know if the CB550 or 500 fork caps would fit the tubes on the 650, or if there's another size/model that would swap?

[Mainerider]

Did you mean to say that you have '81 forks? The '80 didn't have air assist.

[NateTheBookie]

...Hmm... I might have to check on that then, The forks are off my parts bike, which was mostly a skeleton when I got it. I thought it was an '80, but I guess not, I'll have to look up the VIN. Would the '80 650C caps swap in?

[Mainerider]

If I remember correctly, they are the same. Just FYI, I installed the Progressive Suspensions springs in one of my 1980 650s and to get the desired preload I installed a washer and a 3/4 tall piece of PVC piping on top of the springs. For my 175 lb. weight it was just right.

The air assist feature on the '81 was just to allow adjustable preload, in the event of a passenger or other variable load conditions; most often it was used to blow out fork seals by owners using an air hose to inflate  the forks with, instead of the required hand-held bike pump.