Topic: 550 fork internals (clarified); Tube/spring lengths?

[Dimitri13]

One fork bottom is (I assume to be) original to the bike, and the other is an ebay special. All three forks were identical internally.

But they look like this:



No damper rod and locknut, a different shaped damper tube, and no spring seat.

Is this correct? Does it perform differently than the illustration?


I'm installing new Progressive fork springs and new CycleX fork tubes. The springs measure a hair over 19", and the tubes measure between 21-22" (I have them installed already and can only roughly estimate where the bottom is while measuring).

With the tube all the way up and the spring all the way down, the spring sticks out over an inch. This is making it nearly impossible to screw on the cap by myself. I remember my old springs sat below the top of the tube. They were progressive (the style, unsure of the brand) as well. Is this correct or is something out of whack?

[LesterPiglet]

The damper rod was in 500 forks.

[Dimitri13]

Thanks les, I had a feeling that was the case.

[Dimitri13]

Also an issue with fork tube/spring length. Check first post.

[Dimitri13]

Could it be the small "bottoming out" spring is unnecessary and causing the extra height?

[Dimitri13]

Well I received a reply from the company I purchased the springs from:

"What you have is common. Just install them as to the instructions that came with them. The stock spring measurements do not matter when installing Progressive springs. "

Is this true? What are the Progressive spring's measurements supposed to be?

[PeWe]

Here is the instruction to my progressive fork springs I bought end of 80's. Instruction still the same except available on internet in pdf.
http://www.progressivesuspension.com/pdfs/forkSprings/3055.pdf

[Dimitri13]

I have the same instructions. It mentions most forks have springs and spacers that don't go above the top of the tube. Judging by how my old springs were, I'd assume that holds true for this bike.

The spring sticks out over an inch. It's extremely difficult to get the cap on. That seems like way too much preload?

[Dave Voss]

The spring sticks out over an inch. It's extremely difficult to get the cap on. That seems like way too much preload?

When I rebuilt the forks on my '78 CB550, about one inch of spring (which I think are stock) was exposed and needed to be compressed to thread in the top cap, it took some force but was not that difficult to do.  Once assembled and installed, they didn't seem to have too much pre-load (the static sag is normal) so yours may be just fine.

[PeWe]

I removed the 1 inch plastic spacers I used first time. The bike got bad handling with the springs. Heavy front wobble at ~170km/h. OEM springs steady all the way to 210km/h according to the speedo.

Springs will be preloaded by the top nuts with almost 1 inch when springs were max a few mm under the top of fork tube upper position.
Plus followed the instruction of max 140mm oil level without springs and fully collapsed. 199/200cc oil.
My bike is a CB750 K6-76