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Thread: 1985 K100RS aftermarket rear shock.

  1. #1

    1985 K100RS aftermarket rear shock.

    I'm in the process of selecting a replacement rear shock. Ted Porter has told me that their "go-to" replacement for the older K-bikes is the YSS Z series. While I don't want to unnecessarily spend money on a high-end shock that I don't need, I also don't want to waste money on something inferior. So, has anyone here put a YSS on their K-bike?

    Thanks,
    Tom

  2. #2
    Liaison 20774's Avatar
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  3. #3

    Good stuff in there. Thank you.

  4. #4
    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by mcmlcccvrs View Post
    I'm in the process of selecting a replacement rear shock. Ted Porter has told me that their "go-to" replacement for the older K-bikes is the YSS Z series. While I don't want to unnecessarily spend money on a high-end shock that I don't need, I also don't want to waste money on something inferior. So, has anyone here put a YSS on their K-bike?

    Thanks,
    Tom

    I bought a YSS from Tom Cutter for my K75S a number of years ago when YSS was relatively new to the US market. It was a great improvement over the stock shock (most anything is in my opinion) and really improved handling and comfort. Tom had it dialed in for compression/rebound and pre-load settings, and I would buy one again without hesitation.
    Greg Feeler
    Ambassador & amateur K-Bike collector, it seems
    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

  5. #5
    I bought a YSS by the way from Ted Porter.

  6. #6
    Bluenoser
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    You can still get Progressive Shocks that fit the rear of your bike. They have two different length models and then one heavy duty one. Depending on your use, either of the normal ones would be fine. If you are inseam challenged then the lower model would work. If you check Bob's BMW they show them available, and they are on Ebay and a few other places.

    For info purposes I use the Progressive Heavy Duty model on my 1995 R100RT mono with a sidecar and it is really stiff. Works well in that application but unless you where a very heavy individual with a load, then the normal ones would work better on your RS. Not knocking YSS or any other higher end shocks but a lot of us don't need that level of shock, especially on a 35 yr old bike.
    1995 R100Rt with Kenna Sidecar, 1986 K100RT

  7. #7
    Quote Originally Posted by mcmlcccvrs View Post
    I'm in the process of selecting a replacement rear shock. Ted Porter has told me that their "go-to" replacement for the older K-bikes is the YSS Z series. While I don't want to unnecessarily spend money on a high-end shock that I don't need, I also don't want to waste money on something inferior. So, has anyone here put a YSS on their K-bike?

    Thanks,
    Tom
    I went with IKON on my 1995 K75. Very happy.

  8. #8
    +1 on the Progressive shock


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    Brian Hinton
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  9. #9
    Registered User jad01's Avatar
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    FWIW, I have Progressive shocks (rebound and preload adjustable, heavy springs) on one of my air heads- I like them pretty well, and have had them rebuilt once previously. I have them set up to my riding needs, and worked with them to get what I needed. I'm 6 ft, 200lbs.

    I also have a Progressive shock on my K75; I don't like it at all. It's the short shock installed by the prior owner, preload adjustable only, and relatively new (less than 10K miles). I find it doesn't match my needs well. It has too little travel for my taste and too little adjustability within that range of travel. At the softest rebound setting, it bottoms routinely and at the highest setting (the only one where it doesn't bottom) it is very harsh. Replacing it will be the next purchase I make for that bike.

    My point is that regardless of what shock you purchase, I think you are doing well by working with a vendor (Ted Porter) that will help you with sizing and set-up so you are pleased with the result. Any good vendor will help you find a brand that fits your budget and need (they want you back as a customer). I recommend Ted Porter based on my experience, but there are a number of good vendors noted on the forum that would serve you well. I'm sure if that YSS is what he's recommending, it is a good quality product and value.
    Last edited by jad01; 04-15-2020 at 01:29 AM.
    Jim (MOA 83200)
    '78 R80/7 (Anastasia) and '84 R100RS (The Millennium Falcon), '86 K75C (Icy Hot)
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  10. #10
    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by cycleman2 View Post
    You can still get Progressive Shocks that fit the rear of your bike. They have two different length models and then one heavy duty one. Depending on your use, either of the normal ones would be fine. If you are inseam challenged then the lower model would work. If you check Bob's BMW they show them available, and they are on Ebay and a few other places.

    For info purposes I use the Progressive Heavy Duty model on my 1995 R100RT mono with a sidecar and it is really stiff. Works well in that application but unless you where a very heavy individual with a load, then the normal ones would work better on your RS. Not knocking YSS or any other higher end shocks but a lot of us don't need that level of shock, especially on a 35 yr old bike.
    Everyone's tastes are different, but I wouldn't dismiss the handling potential of the classic K-bikes by dismissing them as "a 35 yr old bike." They surely are, but they are also a platform that was well ahead of it's time, and with a dose of modern suspension parts, brakes, and tires, can be both highly enjoyable and very competitive with many more modern bikes.

    The K-series introduced the motor/transmission as a stressed member of a trellis-like frame for BMW, resulting in an extremely rigid system. Although the 2-valve models are limited to bias-ply tires, there are some very modern design tires available (Pilot Actives are one of my favorites). Combine those with modern brake pads (EBC HH for example) either with the stock rotors or something like the EBC semi floating rotors and steel braided brake lines for greatly improved stopping.

    A quality rear shock is about 70% of a bike's suspension in my experience, and today there are some really good options (purpose of this thread). Although many will say they don't need, or can't tell the difference with, a higher end shock, my experience is that most people actually are the Princess and the Pea, and will and can tell the improvement. I have two K75s - one with the basic pre-load-only Progressive and one with a fully adjustable YSS - and they are night and day for comfort and handling, at least for me. The early BMW K-bike front forks are nothing to write home about, but with a good quality set of springs, set to the correct sag and with the right amount and viscosity of fork oil can perform very well, and with a decent shock will run circles around any Airhead for handling. Upgrade them with the Race Tech cartridge emulator kits for a dramatic improvement.

    Naturally, this is all a matter of personal preference, but for myself, I've gotten a lot of bang for the buck on my 2-valve K's with moderate upgrades: suspension, brakes, and tires.
    Greg Feeler
    Ambassador & amateur K-Bike collector, it seems
    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

  11. #11
    GMR 2010 Rally Chair blakduc1's Avatar
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    K100RS Shock Upgrade

    Greg Feeler is spot on with his post, in my opinion. I rode an '85 K100RS for years and many many miles. It had the cartridge emulators in front forks and an Ohlins rear shock. That was the best thing I could have ever done for that bike. It changed it into something much better. Set up right it rode better, handled and was pretty fast. The handling was what really gave it "superpowers" and it could run the mountain twisties faster than folks think the K100RS can. Ran it in the Blue Ridge 500 one year with the other "hooligan" riders going for low times. Took it to some track days, including Road Atlanta. Great for touring and moto camping. Those bikes have many strong points but the suspension was not one of them. It needs the upgrade. That is a good move. I don't know much about the YSS but sounds like it should be good. Probably any really high-quality rear shock would help that bike a lot once set up right. However I strongly encourage you to also get the forks done with cartridge emulators.

  12. #12
    So are you talking something along the lines of Race Tech fork emulators? I wrench my own bike. Is this something I can do?

  13. #13
    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by mcmlcccvrs View Post
    So are you talking something along the lines of Race Tech fork emulators? I wrench my own bike. Is this something I can do?
    It looks like no one replied to your question. I think it would help you to read about how cartridge forks work vs. dampener rod forks. The key part is that cartridge forks (especially the Race Tech cartridge emulators) can provide velocity sensitive dampening whereas dampener rod forks have mostly fixed dampening. The very simplified installation in classic K-bike forks boils down to taking the forks apart, drilling out the dampener rod flow holes until they are so large that they have no effect. Then you reassemble the forks, drop in the cartridge emulators from the top and install the specifed Race Teck springs and oil. This is all documented on the Race Tech web site.

    https://www.racetech.com/page/id/80
    Greg Feeler
    Ambassador & amateur K-Bike collector, it seems
    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

  14. #14
    About 10 years ago I put a YSS shock (from Tom Cutter) on my 92 K75S. It is still there and works great. I've been two up around the US and ridden solo plenty of times.

  15. #15
    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by robsryder View Post
    About 10 years ago I put a YSS shock (from Tom Cutter) on my 92 K75S. It is still there and works great. I've been two up around the US and ridden solo plenty of times.
    Ditto! Same shock for my K75S from Tom Cutter. I don't ride two-up on that bike, but the shock is still working great.
    Greg Feeler
    Ambassador & amateur K-Bike collector, it seems
    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

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