BMW K bikes (Bricks)

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1Back to top Go down   Fork mismatch Empty Fork mismatch on Tue May 21, 2019 10:39 am

Michael Sydney

Michael Sydney
Silver member
Silver member
I am still new to bikes so maybe this is a simple question. I recently bought a 1984 K 100 as a project (I also have an '83 K100 as my regular bike)

The "new" bike had leaking fork seals. Replacement was easy, but when I put back in the yokes found that the two sides are different lengths. To easily slide the axle through I would need to lift one fork tube about 10mm higher in the upper yoke.

Should I simply compress one side to insert the axle with the two uppers level with top of upper yoke?

PS, the fork tubes are certainly in the same plane, just length difference.


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Living in the past! K100 '83 and R65 '83.
    

2Back to top Go down   Fork mismatch Empty Re: Fork mismatch on Tue May 21, 2019 2:39 pm

tinyspuds

tinyspuds
Life time member
Life time member
Someone on here with BMW teles will tell you the likely cause and resolution. But in the meantime do not attempt to ride with one leg compressed as you suggest.Fork mismatch 797640


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1985 BMW K100RT + Hedingham HUB and LL’s. VIN 0028106. (Not blind to the irony of an April 1 production date).
1954 Royal Enfield 350 Bullet. Original.
    

3Back to top Go down   Fork mismatch Empty Re: Fork mismatch on Tue May 21, 2019 6:49 pm

Snod Blatter

Snod Blatter
Life time member
Life time member
To be clear, that is not normal!

Are you sure they're the same type of fork? Are the markings on the inside near the mudguard the same on both?


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1989 K100RS SE ABS 8v  VIN: 0149214
Others: 1.5 x Honda CBX250RS-E, '94 CB250, '95 TRX850, '16 Z250SL
http://justbikethings.blogspot.co.uk/
    

4Back to top Go down   Fork mismatch Empty Re: Fork mismatch on Wed May 22, 2019 12:08 am

Basic2

Basic2
Platinum member
Platinum member
Michael, you didn't miss a spacer when you were reassembling one leg?


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K100 Basic 2
11/1987 6308319K100CJ
Marakesh Red
    

5Back to top Go down   Fork mismatch Empty Re: Fork mismatch on Wed May 22, 2019 2:01 am

chris846

chris846
Life time member
Life time member
I think you need to strip the forks. It's possible (but not the only explanation) that one is incorrectly assembled - if the damper rod isn't seated correctly in the bottom of the slider then the assembled fork will seem 'longer'.

The damper rods are retained by a single bolt which is accessed through the bottom end of the slider. Undo that bolt before you remove the spring - that'll stop the damper rod from turning.


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Sometimes I'm not really Suzi Quatro.
    

6Back to top Go down   Fork mismatch Empty Re: Fork mismatch on Wed May 22, 2019 9:01 am

Laitch

Laitch
Life time member
Life time member
@chris846 wrote:I think you need to strip the forks.
Indubitably. Smile

Michael's posts on this forum about his moto don't seem to indicate that the fork assembly has been thoroughly inspected, maintained with oil replacement, or checked after damage that might have occurred in accidents since he has owned it. It's conceivable that extension and compression are being effected by lack of fluid viscosity, sludge, broken or fatigued springs, and maybe bad bushings.

Disassembling of the fork legs, confirming correct assemblies, cleaning their tubes, inspecting the bushings, springs and other parts, then replacing what might be worn or damaged should be undertaken. After that, they could be measured.


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1995 K75 77,000 miles
Fork mismatch Usa-lo10
    

7Back to top Go down   Fork mismatch Empty Re: Fork mismatch on Wed May 22, 2019 9:49 am

Michael Sydney

Michael Sydney
Silver member
Silver member
A few more details!

I dismantled the forks, one at a time, and reassembled as I found them. The axle was tight on removal and required some force to remove but this was probably due to a little corrosion but I have since cleaned and oiled it.

No spacers that I found. The damper rods fastened easily to the single bolt at the bottom. Springs went back in with end pieces in place and correct amount of oil into each thoroughly cleaned assembly.

I will disassemble them again and compare the damper rod lengths.


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Living in the past! K100 '83 and R65 '83.
    

8Back to top Go down   Fork mismatch Empty Fork mismatch solved on Fri May 24, 2019 1:46 am

Michael Sydney

Michael Sydney
Silver member
Silver member
Well, it was simple, but not what I expected.

Earlier I just replaced fork seals so had not touched the damper rods. Today I removed the forks again and found a definite mismatch in rod length so removed both dampers from the stanchions.

The damper assembly is held together by screwing the piston down the rod to achieve a length of 258 mm according to Haynes. One piston was loose, the other nearly falling off! Clearly the thread locking compound had failed.

So, no lost parts, nothing broken, but a 24 hour wait for the Locktite to set, then the fun of getting the damper with piston ring back in place Smile


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Living in the past! K100 '83 and R65 '83.
    

9Back to top Go down   Fork mismatch Empty Re: Fork mismatch on Fri May 24, 2019 4:18 am

TacKler

TacKler
Life time member
Life time member
Good news then Michael.  

Meanwhile as the Loctite is setting you could do a run up to Sofala on one of the other bikes?   Wink


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Red 1991 K75S
    

10Back to top Go down   Fork mismatch Empty Re: Fork mismatch on Fri May 24, 2019 8:21 am

Michael Sydney

Michael Sydney
Silver member
Silver member
@TacKler wrote:Good news then Michael.  

Meanwhile as the Loctite is setting you could do a run up to Sofala on one of the other bikes?   Wink
Ah yes, there are some members there this weekend? Never quite understood the post, started in 2017, and nothing in the calendar. Perhaps organised rides could be made a sticky to get attention?

Anyway, a long solo ride and no booked accommodation. Maybe next time.


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Living in the past! K100 '83 and R65 '83.
    

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