Are K75 / K100 Front Fork Springs Identical

[AgPete139]

Howdy guys,

I'm the proud owner of a red 1987 K75C that I brought back to life 2 months ago. I got her for $850, with just shy of 4k miles. She hadn't been ridden since 1991. I went to register her and the Tax Office did a double take at the last registration date & mileage.  :dunno  It was entertaining.

At any rate, I have been lurking and using Google to search MotoBrick for answers. So, I searched before I ask this question...  :nono I have performed all work myself, minus the new fork rebuild using Progressive springs, BMW seals, and 15W fork oil (Progressive's recommendation.)

The spongy-feeling right fork was leaking, I am told. I am not sure why, but it was worn to the point that the fork seal has trouble sealing and it will slowly leak fluid again. The bike mechanic put in an even HEAVIER weight oil for this reason. It's way, way too stiff.

K75's like the K100 fork upgrade for the better brakes, etc.

WILL I BE ABLE TO USE MY K75C PROGRESSIVE BRAND SPRINGS IN K100 FORKS IF I OPT TO DO THE SWAP? WILL I BE ABLE TO MATCH THE SPRING PRELOAD AND CENTER IT WITH THE SPACERS ACCURATELY?


Thanks in advance for any help. I decided to finally sign up after seeing such a polite and helpful community.

Pete

[johnny]

greetings agpete139...

welcome to motobrick...

when i do fork seals i also do the upper and lower fork bushings cause thats generraly the reason for mechanical leaks... and of course a sealmate type device for debris leaks...

have run 7.5wt 15wt  20wt before... im in the 10wt camp right now...

j o

[mjydrafter]

I think it depends on the forks, K100 vs. K75.  My bike originally had a set of non-braced K100 forks.  I swapped them out for a set of braced K75 forks.  I think the brace helps a lot.

That would be the biggest thing to consider.

It looks like the PN is the same from a K75 to a K100 on the Progressive's, so to answer your question they should work if you get 1987 k100 forks, but I think you'll lose the brace.  And they take a different 1 piece fender. 

You might look through some of Duck's posts, I'm pretty sure he has swapped about anything that can be, including a better, later front end.

[AgPete139]

Thank you.

I'll give it another look. I love the library.