New front end for K75

[kedw44@gmail.com]

I am thinking about swapping out my forks for either a Suzuki, Honda or Yamaha front end. I know of a handful of companies that make triple trees, stems and other parts for this but am unclear about what wheels, brakes, spacers and whatever else may be needed and used. Does anyone have experience with this?

 

[pglaves]

I am thinking about swapping out my forks for either a Suzuki, Honda or Yamaha front end. I know of a handful of companies that make triple trees, stems and other parts for this but am unclear about what wheels, brakes, spacers and whatever else may be needed and used. Does anyone have experience with this?

I'm curious. Why? What year/model K75?

 

[kbasa]

I am thinking about swapping out my forks for either a Suzuki, Honda or Yamaha front end. I know of a handful of companies that make triple trees, stems and other parts for this but am unclear about what wheels, brakes, spacers and whatever else may be needed and used. Does anyone have experience with this?

Cognito moto has a variety of solutions for you: https://cognitomoto.com/products/gs...0-frame-conversion-stem?variant=3724292522024 In this, you guy a modern GSXR fork and swap out the stem, retaining the original triple trees, which is a fairly elegant solution. Getting a master cylinder to work with the calipers will present some potential challenges.

I keep having thoughts of an R100R with a modern fork and brake setup with a modern radial up front and a K11 wheel on the back sporting modern rubber.

FWIW, I put RaceTech stuff in my airhead and it made a world of difference in compliance and control, so that may be an option for you that will get you modern innards without having to graft a whole assembly on up front.

 

[98lee]

I'm curious. Why? What year/model K75?

My questions also. Does your bike have the Showa or the Fichtel-Sachs forks? Sport or non sport F-S?

What are you trying to accomplish that you couldn’t do with spring and oil tuning?

Are you planning on also changing the rear to paralever?

 

[kbasa]

Cartridge style forks are a huge improvement over damper rod forks.

Add in the seriously better brakes that come with these modern forks and you've upgraded not only your suspension compliance and performance, but you're getting modern braking capabilities, too.

I elected to swap the innards for RaceTech cartridge emulators on my R100 and it made a big difference, but it's nowhere near the performance a more modern true cartridge. Add in an ability to use radial tires and it's a big step forward for a K75. I'd go with the K11 rear wheel that holds a radial rear tire, as well.

Modern rubber on both ends. Upgraded braking up front. Far better compliance and the unsprung weight advantages of a male slider fork will bring a K75's fairly primitive front suspension into the modern age.

 

[98lee]

An Airhead is a generation before the Bricks. Even more antiquated.

At the time, the K75S with the Sport suspension,was declared by the motorcycling press, “the best handling BMW by a good margin”.

If you are trying to get a modern bike, why not just buy a used modern bike. It would be less expensive.

 

[lee]

Cartridge style forks are a huge improvement over damper rod forks.

Add in the seriously better brakes that come with these modern forks and you've upgraded not only your suspension compliance and performance, but you're getting modern braking capabilities, too.

I elected to swap the innards for RaceTech cartridge emulators on my R100 and it made a big difference, but it's nowhere near the performance a more modern true cartridge. Add in an ability to use radial tires and it's a big step forward for a K75. I'd go with the K11 rear wheel that holds a radial rear tire, as well.

Modern rubber on both ends. Upgraded braking up front. Far better compliance and the unsprung weight advantages of a male slider fork will bring a K75's fairly primitive front suspension into the modern age.

Thanks for the explanation. I can see these mods being worth it if the person has the ability to do the work.
It's no different than taking a 60s muscle car and using modern brakes, suspension and steering to make it more fun to drive.

 

[kbasa]

An Airhead is a generation before the Bricks. Even more antiquated.

At the time, the K75S with the Sport suspension,was declared by the motorcycling press, “the best handling BMW by a good margin”.

If you are trying to get a modern bike, why not just buy a used modern bike. It would be less expensive.

Where's the fun in that?

Note that the K75 was delivered 38 years ago. If you can score one for short money, and there are plenty, along with a few hundred bucks for an entire front end and bolt it up, why not take this opportunity to retain that old school K bike, but with far better running gear? Damping rod suspensions were largely gone from bikes by 2000, so why not take the opportunity to make it work better? I think I was all in for $400 on the Racetech emulators and it took me a weekend in my garage to do.

And the entire time, I was thinking that a Cognito steering stem and a late model fork would work even better.

I keep thinking I need a late R100R for this treatment after adding floating rotors, radials and cartridge emulators to my R100. "How much more awesome would this bike be with real running gear?"

Different objectives, I guess, but I'm all for modernizing old stuff to make it work even more like the designers hoped it would.

 

[kbasa]

Thanks for the explanation. I can see theses mods being worth it if the person has the ability to do the work.
It's no different than taking a 60s muscle car and using modern brakes, suspension and steering to make it more fun to drive.

You bet. It's not hard to swap the front end. Take fork legs off the new front end, press the stem out of the bottom triple tree, press the Cognito moto one in and bolt it up. Sort out braking and a fender and you're good to go.

Reminds me of the 356 Outlaws in Porsche land.

 

[kedw44@gmail.com]

The bike in question is a ‘87 K75c with F&S forks. I want the superior handling and stopping of a Japanese front end. I am aware of Cognito Moto and three other makers of parts for this. I am hoping to be in touch with someone who has successfully made this swap.

 

[98lee]

So you’re going to go for superior braking with a rear drum brake?

The ‘87 K75C did have terrible front handling because it had 2” more front travel than any other K. The damping on those early C forks was really bad too. Brake dive made the bike no fun to ride.

You have much more than forks to make that bike handle and stop$$$ Good luck.

You might want to research the cost of getting the right throttle/ brake lever perch and master cylinder BEFORE you commit to the conversion.

 

[pglaves]

Mine, Old Smokey, which died in an accident at 370,000 miles was an '86 with those same forks. When the parts became available I removed all of the fork innards and replaced them with parts for the K75S. Then a little tweaking of the spring preload spacers and the volume and viscosity of the fork oil transformed the handling of the bike. I was happy with the change.

 

[98lee]

Mine, Old Smokey, which died in an accident at 370,000 miles was an '86 with those same forks. When the parts became available I removed all of the fork innards and replaced them with parts for the K75S. Then a little tweaking of the spring preload spacers and the volume and viscosity of the fork oil transformed the handling of the bike. I was happy with the change.

Yep

The early K75C was the only K75 that didn’t come standard with the very capable F &S Sport forks or the Showa forks.

 

[pglaves]

Yep

The early K75C was the only K75 that didn’t come standard with the very capable F &S Sport forks or the Showa forks.

The K75T too but it was just a C with a better seat,different headlight, no little fairing but better windshield and bags.

 

[jawjaboy]

I put Progressive fork springs in my '86 K75C forks which helped the ride and handling but I didn't/don't have anything to compare it to so it might still be bad handling. [emoji23]


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