BMW K bikes (Bricks)

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1Back to top Go down   Front-end Vibration Empty Front-end Vibration Mon Nov 08, 2010 4:08 am

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My K100RS has had BMW-made accessory bars fitted. The riding postion is very comfortable as they are higher, however, I get a numb left hand riding at around 4,000 rpm. I'm trying to locate the original bars to see whether they make a difference although they'll be much lower.

Another thing is the low-ish speed wobble from the front-end. Is there any way to get rid of it or, at least, dampen the effect?

Thanks, Martin

    

2Back to top Go down   Front-end Vibration Empty Re: Front-end Vibration Mon Nov 08, 2010 5:04 am

Crazy Frog

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Martin,

The vibration at around 4,000 rpm is the trademark of the K100 Very Happy and I don't think replacing the bars will change anything.

On my K100, I can take my hands off the handle bar at any speed and the front end doesn't move at all.
A front end wobble can be the result of many different problems and the goal is not to damp the effect but to find the cause and fix it.
it could be:
- Tire not balanced properly (most common cause) - Try the Dynabeads -
- Worn tire
- Triple tee bearing too tight (usually this implies a heavy steering at low speed)
- Wheel bearings worn (very easy and cheap to replace)


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Front-end Vibration Frog15Front-end Vibration Logo2101986 k75, 1985 K100rt, 1985 K100rt/EML GT2 sidecar, 1999 K1200lt/Hannigan Astro Sport sidecar.
    

3Back to top Go down   Front-end Vibration Empty Re: Front-end Vibration Mon Nov 08, 2010 5:09 am

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The tyre is almost new, it was fitted before I bought the bike. I'll check whether it has been properly balanced though. I think that could be an issue as the bars turn easily.

    

4Back to top Go down   Front-end Vibration Empty Re: Front-end Vibration Mon Nov 08, 2010 9:57 pm

K-BIKE

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Get someone to sit on the rear of the bike on the centre stand and then see how it feels as you turn the front wheel back and forth with it off the ground,
Is there any notchiness in the centre? Then try to pull the forks (holding at axle level), forward and back is there any movement?
Regards,
K-BIKE

    

5Back to top Go down   Front-end Vibration Empty Re: Front-end Vibration Tue Nov 09, 2010 1:39 am

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Not only checking the points above, but surely returning the handlebars to spec will alter the frequency of the vibration felt at the bar ends?

    

6Back to top Go down   Front-end Vibration Empty Re: Front-end Vibration Mon Nov 29, 2010 3:15 am

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I have mentioned before, my bike has higher and wider "Comfort" bars, almost 27" across compared to the original 22"! But one thing was bothering me, the choke light would come on on full lock, not too important but not ideal. This weekend I decided to chop 2 cms off each end of the handlebar. Obviously this has cured the choke cable issue but it also seems to have reduced the vibration I was feeling. I can also get a better rear view in the mirrors although I just might get a set of spacers to push the mirrors out just a little more.

    

7Back to top Go down   Front-end Vibration Empty Re: Front-end Vibration Mon Nov 29, 2010 3:17 am

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@K-BIKE wrote:Is there any notchiness in the centre? Then try to pull the forks (holding at axle level), forward and back is there any movement?
Regards,
K-BIKE

Checked this weekend, there is no notchiness in the headraces.

    

8Back to top Go down   Front-end Vibration Empty Re: Front-end Vibration Mon Nov 29, 2010 6:50 am

japuentes

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Martin K100RS wrote:Another thing is the low-ish speed wobble from the front-end. Is there any way to get rid of it or, at least, dampen the effect?

Hi there, check the rear strut, wen worn/loose it causes/increases the front wobble at low speed.
Best regards
JAP

    

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