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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: ed3541 on October 24, 2019, 10:18:36 AM

Title: K 75c Fork Springs
Post by: ed3541 on October 24, 2019, 10:18:36 AM
Hi,
I have a 1995 K75c with squishy forks. A mechanic supposedly rebuilt my forks but the fluid leaked-out on to my brakes. I'm wondering if I can install fork springs in both tubes (like my old K75s). Does anybody know what parts I'm gonna need to put springs in both forks?
thanx,
Ed




Title: Re: K 75c Fork Springs
Post by: Laitch on October 24, 2019, 10:43:27 AM
The K75C's last year of production was 1990. If yours is a 1995, it isn't a C-model.

A 1995 K75 should be equipped with a Showa fork unless the entire assembly had been swapped with an earlier model. The Showa tubes have external diameters of 41mm. The internal parts of both the left and right Showa tubes are identical. There already are springs in both tubes. First, determine the size of the tubes.

Your fork is squishy likely because there is little fluid in it. Did the fluid leak from the seals around the tube? Your mechanic might have used aftermarket seals. Original equipment seals are preferred.
Title: Re: K 75c Fork Springs
Post by: ed3541 on October 24, 2019, 01:59:10 PM
Thanx Laitch,

I'm gonna get some OEM seals.

Ed
Title: Re: K 75c Fork Springs
Post by: Laitch on October 24, 2019, 02:38:29 PM
Take a close look at those tubes, ed. If they are pitted where they enter the lower tube, they are likely to make any seal leak.
Title: Re: K 75c Fork Springs
Post by: Martin on October 24, 2019, 04:32:30 PM
To extend the life of your seals pack heavy silicone grease between the seal and the dust cover. It stops road crud from getting to the seals and probably keeps them lubed and flexible. Change the grease occasionally more often in dusty conditions. I changed the seals on my brick when I first got it over 20+ years ago.
Regards Martin.
Title: Re: K 75c Fork Springs
Post by: The Mighty Gryphon on October 25, 2019, 07:06:58 PM
Headlight isn't K75.  Probably isn't a K75S because those had 3 spoke wheels.  That would make it likely to be a chopped up RT. 

If I remember right, the RT had longer travel softer forks than the other models, and I think they used a couple more ounces of oil as well.  If they weren't filled properly, I could see them being pretty soft and squishy.  Brake dive on my K75RT can be pretty alarming at times even when filled with the correct amount of fluid.
Title: Re: K 75c Fork Springs
Post by: Chaos on October 25, 2019, 07:48:31 PM
It's been cut up, missing rear cowl. Hard to say what it started out as.  Didn't RT's have the radiator hose outside the crankcase cover?  Or am I just getting senile?
Title: Re: K 75c Fork Springs
Post by: Past-my-Prime on October 25, 2019, 08:22:56 PM
It's been cut up, missing rear cowl. Hard to say what it started out as.  Didn't RT's have the radiator hose outside the crankcase cover?  Or am I just getting senile?

Mine's an RT and the radiator hose goes through the fairing, not through the crankcase cover.
Title: Re: K 75c Fork Springs
Post by: Martin on October 25, 2019, 09:13:11 PM
It's got 75s mirrors with the more streamlined back. And early 75s's did have the eight spoke wheels. What's on the compliance plate?
Regards Martin.
Title: Re: K 75c Fork Springs
Post by: volador on October 25, 2019, 10:51:00 PM
Has the proper K75S petrol tank, indentation just above the lowest lobe & fairing prong tank front & tastefully removed side mounting hole,
K75S handlebars and as stated the streamlined/rounded back mirrors
'95 may or may not have 50A alternator

K75 Brembo: 41,3
K75 Showa: 41,0

http://www.motobrick.com/index.php?topic=5606.0
http://www.k100-forum.com/t2921-fork-oil-k75
https://ibmwr.org/index.php/1998/06/01/fork-spring-installation-tips/
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/showaprog/showaprog.htm
https://www.realoem.com/bmw/en/showparts?id=0572-USA---K569-BMW-K+75+S+(0563,0572)&diagId=31_0923
https://www.realoem.com/bmw/en/showparts?id=0572-USA---K569-BMW-K+75+S+(0563,0572)&diagId=31_0924
Title: Re: K 75c Fork Springs
Post by: volador on October 26, 2019, 10:26:08 AM
https://www.youtube.com/watch?v=tVWHfyG4jB4

https://www.youtube.com/watch?v=gRnAhiClzoY

https://www.youtube.com/watch?v=TVMr25fnTnU
Title: Re: K 75c Fork Springs
Post by: Laitch on October 26, 2019, 10:48:08 AM
'95 may or may not have 50A alternator
A 1995 original K75 will have the 50A alternator but like any used moto. parts might have been swapped along the line. ed needs to run the last seven digits of both his motos' VINs through the realoem VIN checker (https://www.realoem.com/bmw/select.do?kind=M&arch=1) to determine what the motos might have been originally.
Title: Re: K 75c Fork Springs
Post by: ed3541 on October 26, 2019, 01:08:28 PM
A 1995 original K75 will have the 50A alternator but like any used moto. parts might have been swapped along the line. ed needs to run the last seven digits of both his motos' VINs through the realoem VIN checker (https://www.realoem.com/bmw/select.do?kind=M&arch=1) to determine what the motos might have been originally.

Yes I did the Vin# search and determined that it is a K75 not a K75c
thanx,
Ed