BMW K bikes (Bricks)


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1Back to top Go down    K100 cafe racer build on Thu Jul 21, 2016 4:23 pm

tyetye

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Looking for some info.
me and my son's are building a cafe racer with my k100. 
I'm looking for a rear shock that's an inch or 2 longer than the standard RS model. Something from another bike maybe to try and keep cost down
thanks.

    

2Back to top Go down    Re: K100 cafe racer build on Fri Jul 22, 2016 11:26 pm

Holister

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You could try a shock off a K1100 or other later model K100 with paralever rear-end. They measure 385mm. A std K100 is about 350mm. So you'd get about 1˝"
The problem with this is you will push the driveshaft down a few more degrees and and place more stress on the uni-joint because the driveshaft is already angled down to start with and you'd be pushing the driveshaft past its normal range of movement.
You'd also be changing the geometry of the frame slightly and placing more weight forward. The front end would probably become a bit more responsive.
Also, I think the paralever shock is a little stiffer due to it's bottom mount being a little further back placing it at a less upright angle.

Just my thought. Cheers


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1988 K100RT     VIN No.  0094680
1989 K100RT     VIN No.  0097367 (naked)  
1996 K1100RS   VIN No.  0451808
     Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

3Back to top Go down    Re: K100 cafe racer build on Sat Jul 23, 2016 3:52 am

K75cster

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Does anyone know if the R100gs uni joint is different to ours, as they have a greater angle and behave just fine mile after mile. Gaz what about the R80gs, is it a greater angle than the k's you own?
There must be a safe range to operate in.


__________________________________________________
Keith - 1987 K75c with r100rt replica fairing and half of a 1984 K100rt

The Clever are adept at extricating themselves from situations that the wise would have avoided from the outset - QUOTE from david Hillel in Out of the Earth.
    

4Back to top Go down    Re: K100 cafe racer build on Sat Jul 23, 2016 4:11 am

RicK G

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Uni joint range 0° to 16° for continuous running with 24° as an occasional maximum.
At 0° the rollers dont spin and so leave marks across the inner and over 16° the rollers will spin fast enough to generate excessive heat leading to the eventual destruction of the bearing surface and ultimate failure.


__________________________________________________
If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

5Back to top Go down    Re: K100 cafe racer build on Sun Jul 24, 2016 7:19 am

andyldean

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If its height you are after I mounted my seat a little higher on the frame.

I have seen what looks like a second hope welded on top of the frme to give the same result


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1987 K100RT (cafe racer)
1991 K100RS (soon to be my sons cafe racer)
    

6Back to top Go down    Re: K100 cafe racer build on Sun Jul 24, 2016 8:58 am

Garyk100

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Years ago I got a set of Koni shocks for a xs850 yammy, they were a a bit longer maybe inch and half, made it sit up higher, but was scary trying to go around corners it just wanted to go straight, put a set of xs1100 shocks on and was perfect, just my experience so maybe Ks are different. Gary


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The early bird catches the worm, but the second mouse gets the cheese

1991 K100rs16v
1993 K1100LT
    

7Back to top Go down    Re: K100 cafe racer build on Sun Jul 24, 2016 9:39 am

indian036

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I'm with Garyk100.
Apart from the angle of the driveshaft Uni joints (Rick G),lifting the back end will change the steering rake angle. I don't have enough expertise to say how much of an issue it would be, but without serious expert input I'd be reluctant.

Sort-of relevant experience was with a Mini Cooper S. For a short time, the springs which pull the rear end down on the hydrolastics were not fitted. The extra ride height at the rear changed the steering geometry so much that it was difficult to go around any corner without tyre squealing.

Also on Uni joints, someone who raced minis used to have the suspension height set so he driveshafts were horizontal. He attributed his success at the time to the competitors who had their minis lowered as much as possible losing energy from inner uni joints running permanently angled, in otherwise very comparable cars.

Rear ride height on mini was personal experience, drive shaft angle hearsay, but direct from the person who did it and very knowledgable about minis in both road and racing settings.

Bill


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1985 K100RT  VIN 0028991  My original Very Happy   (Historic rego)
1985 K100RT  VIN 0029036  BOB the Blue Old Bike  (Historic rego)
1990 K100LT  VIN 0190452  Work in progress
1984 K100RT  VIN 0023022  Work needing lots of progress

1986 K100RT  VIN 0090542  Work needing lots and lots of progress
1993 K1100LT  VIN 0183046  Work in progress
1993 K75S  VIN 0213045  Newest toy, slightly non-original
    

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