BMW K bikes (Bricks)

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51Back to top Go down   Front end wobble - Page 2 Empty Re: Front end wobble Mon May 04, 2020 5:33 pm

volador


Life time member
Life time member
@DeanG wrote:Surprise! Last week I installed a Laminar Lip.windscreen extension. I tried adjusting the little BMW lip to allow more air to flow under the Lip. Guess what? The wobble seems to have disappeared! Still seems too sensitive if this minor adjustment makes a difference. My intention is to move ahead with rebuilding front forks and replacing rear shock.

When you thought you read every thing a Laminar Lip wobble, bloody brilliant

Progressive springs and Ohlins rear damper to match your moto color nicely. ride on

    

52Back to top Go down   Front end wobble - Page 2 Empty Re: Front end wobble Mon May 04, 2020 10:21 pm

DeanG

DeanG
active member
active member
I intend to install new shock and springs. Probably go with Progressive components. Ohlins seem a bit too pricey for me...

    

53Back to top Go down   Front end wobble - Page 2 Empty Re: Front end wobble Tue May 05, 2020 5:02 pm

gorio

gorio
Silver member
Silver member
Wow. i wonder how that works? A laminar lip making some sort of turbulence that is upsetting the bike?
I had a Kawasaki Concours that tried to kill me the day I bought it. Both hands on the bars between 80-50kph when rolling off was the only safe way to ride it. A fairly common problem with that bike. Guess what finially fixed it?
There was one guy who answered every post about head shakes, low speed wobbles, and high speed wobbles the same way, Head Bearings. He would insist that they were worn, improperly adjusted or improperly installed. People would change tires, wheel bearing, springs, shocks you name it and although many of these thing would sometimes contribute to the problem nearly every one come back in the end with it being head bearings in one form or another.
I know you have said your mechanic has changed out the head bearings But did they pull the races quite often a really rotten job to do? Did the new races go in properly. Have they been adjusted properly and re-adjusted after seating in?
Before spending bags of money on other things I would pull the steering head apart and have a real good look. Maybe even pull and replace the races, Clean, check, re-lube the bearings and adjust them one more time. Way cheaper then replacing suspension. New springs and shocks are very nice improvement but may not be the answer.

Two cents worth.

    

54Back to top Go down   Front end wobble - Page 2 Empty Re: Front end wobble Tue May 05, 2020 5:16 pm

MartinW

MartinW
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I had to adjust and readjust my bearing 3-4 times before I got it right.
Regards Martin.


__________________________________________________
K75s Hybrid
    

55Back to top Go down   Front end wobble - Page 2 Empty Re: Front end wobble Tue May 05, 2020 5:24 pm

gorio

gorio
Silver member
Silver member
@MartinW wrote:I had to adjust and readjust my bearing 3-4 times before I got it right.
Regards Martin.
Good man for sticking with it rather then throwing parts at it. Any secrets to success to pass along?
I have been lucky with my BMW's they have all tracked pretty smoothly. I do usually do wheel bearings and head bearing in bikes new to me just because I like to know hold old they are for sure.

    

56Back to top Go down   Front end wobble - Page 2 Empty Re: Front end wobble Tue May 05, 2020 5:37 pm

Dai

Dai
Life time member
Life time member
Dean - if you have the time, try this.

1. Disconnect all control cables and the wiring from around the headstock i.e. instrument panel, left and right switches (you'll need to hang these forward of the forks), throttle, clutch and fast idle. If you can't easily disconnect the control cables, make sure there is as much slack in them as possible where they curve up to the handlebars. Make sure they don't catch anywhere when you move the bars from lock to lock

2. Jack the front of the bike up until the front wheel is just clear of the ground

3. Centre the handlebars

4. Put both hands one on each of the fork bottoms. Gently try to rock the steering assembly from front to rear. You are testing for the slightest amount of play - there should be absolutely none. Don't be fooled by the bike moving, which is why I said 'gently'. Any movement might be removable but... read on

5. Hold one end of the handlebars lightly in your fingertips and move the steering assembly from one side to the other. It should be absolutely smooth. Any feeling of 'tick-tick-tick' resistance coming through the bars is a sign of brinneling in (most likely) the lower headstock bearing outer raceway. 'Brinneling' is where the taper rollers have punched a groove in the outer raceway. This is a replacement job.

6. Make sure the handlebars are still centred. Tap the end of the bar sharply but not hard. The whole steering assembly should fall off to the otherside in one smooth motion. Any sign of resistance, first check that you're not snagging any of the cables. If there's no obvious snag then your headstock bearings are possibly too tight.

7. If you don't find any signs of brinneling, then (4) could be the headstock bearings being slightly too loose

Loose, tight or brinneled headstock bearings will all cause a weave. I don't know about Clymer but Haynes have lifted the BMW description of how to set the headstock taper rollers verbatim from the OEM workshop manual. That description assumes that the outer taper raceways are not fully seated after they have been pushed/pulled in. I always keep at least one outer raceway from every taper roller bearing I have ever changed. I tap the raceway flush with the headstock, then use the old raceway to drive the new one fully home. It goes in approximately a further 2mm from flush. I then adjust the bearings so that the tap test (6) is stiff. From there, I slacken off the adjuster in tiny increments doing the tap test while still testing for looseness (4). When the tap test moves quickly and smoothly but there is no looseness, the bearings are properly adjusted. This assumes that you did seat the outer raceways as described.

There are other methods for setting taper rollers but most of them assume the outer raceway is not fully home and start by getting you to keep tightening up the bearings until the bearing is pulled hard home. I don't like this method because if you're not familiar with the procedure, too much pressure can start brinneling in a brand new bearing.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

57Back to top Go down   Front end wobble - Page 2 Empty Re: Front end wobble Tue May 05, 2020 5:58 pm

volador

volador
Life time member
Life time member
'tick-tick-tick' BADA BOOM


__________________________________________________
1984 K100RS  1991 K100RS  Reap The Wild Wind... Ever Commute Is An Adventure
    

58Back to top Go down   Front end wobble - Page 2 Empty Re: Front end wobble Tue May 05, 2020 8:06 pm

DeanG

DeanG
active member
active member
Wow! Thanks for steering head bearings tutorials. New steering head bearings were installed and subsequently adjusted by a very competent BMW mechanic. Pretty sure this is not the problem.



    

59Back to top Go down   Front end wobble - Page 2 Empty Re: Front end wobble Tue May 05, 2020 11:36 pm

MartinW

MartinW
Life time member
Life time member
I had trouble with the knurled nut and ended up using a heavy duty strap wrench to get purchase.
Regards Martin.


__________________________________________________
K75s Hybrid
    

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