New K75 owner, need fork seals

[90K75]

Hi all,

I'm a new K75 owner. Its a 1990 with about 50,000 miles. Everything seems to work pretty good on it but the front fork seals leak. I looked on Max BMW and there are various part numbers even within 1990. What's the best way to figure out which seals and bushings I need? I have done this on a GS 500 before and it was fairly easy. I have watched youtube videos for the K bike.







Thanks
Dylan

[rbm]

Try first cleaning out between the seals and tubes using a special shaped plastic, Sealmate I think it is called.  An old fashion 35mm negative works also.

[Laitch]

The best way to figure out which bushings and seals you need is first to disassemble the fork legs then compare what you have with the parts in the MAX diagrams. I find two gasket rings (fork seals) listed for the K75 at MAX—pre-08/91 or 08/91 on. Order a couple for your bike based on either where your bike's year lands in those ranges, or by the appearance and measurement of the parts after disassembly. You can also order based on a lucky guess. My experience with MAX is that they ship quickly.

The Sealmate/film negative seal cleaning can work and Sealmate has videos on Youtube showing the technique. It may work more effectively if it's used when the leak is first discovered. If the bike is ridden while the seals leak, oily grit may infiltrate the brake assembly resulting in more work.

Your bike appears to be an RT. Did you run the VIN through an online checker to verify its year and model?

[johnny]

greetings 90k75...

that motobrick is not oem or nearly oem and its not all there... has a modified rs faring upper... hard to say why... wad up perhaps... the forks may not be for the vin either...

id 1st try the sealmate or similar... if you are gonna do the seals id do the upper and lower bushings at the same time... gotta figger it out like laitch laid out...



j o

[Scott_]

Dylan, Greetings and welcome.
I won't comment on the forks, but I will say that you might want to check your gas cap assy. I see in the pictures that the hinge is mounted forward.
Normally the hinge is to the rear. There is a reason for this.
On the left side there is a hole/notch for the purpose if draining rain water from under the gas cap. Unless a PO modified the cap mounting(drilled another hole), yours is most likely covered and blocked.

Nice looking bike.

[90K75]

Thanks everyone,

I will try the sealmate but I think so much fluid is gone, I need to fill it anyway. It nose dives hard.

Gas Cap - it current flips forward, thanks for the tip that it should come backward

Fairings - it seems like an odd bike. Either someone broke a mirror off and then replaced it with stalk mirrors, or it was more stripped bike that the fairing was added to.

I haven't found any real mechanical monkeying yet. Shaft splines are the next task.

Thanks
Dylan

[johnny]

greetings...

its the fork springs that effect the nose dive more than anything...

id drain the forks and fill them with automatic transmission fluid to spec levels before going any farther... a t f will cause the seals to swell... ride it a couple hundert miles and try the sealmate... drain and fill with honda ss8-10 10wt suspension fluid... that and new fork springs may be all it needs...

there is more whack to that moto than a mirror... butts it may turn out to be a good runner...

j o

[90K75]

The VIN checks as a RT.

Jonny, the bike was bought as a project, so I'm more interested in the mechanicals. Any other hot button items I should check? I'll drain the forks and refill. Probably get progressive springs. Next on the list if the spline check. Sealmate ordered as well.

[The Mighty Gryphon]

Nothing to add except that I am really digging on that RS fairing.  Especially how the pop off mirror/turnblinker assemblies have been removed.  The wheels are turning, and I am beginning to think I need another K75 project.  Something like a K75 in an 11 hundert RS fairing.  Or maybe just a bikini RS fairing.  Oh crap...

[K1300S]

nice corbin seat...don't see those very often.  it is really darn low though.  i can flat foot...while on the center stand.