Wobbles

[79beem]

Did I mention the strong handlebar wobbles at 60kph, if i ride one handed? ( No hands gets real bad,real quick).  

<57/63>kph it settles down again.

Put her up on the center stand and turned,tugged and pushed the front around with nothing evident from my bullying.

Did much the same to the wheel to no avail.

There is a small amount of fork fluid sitting under the fork cap on the yoke.

Any ideas chaps?  :-?  

[Barry]

If it did that with no hands it might be considered normal. Even one hand though should be enough to damp out any oscillations.

Could be a number of things but first thing to check is correctly adjusted steering head bearings. Correctly adjusted means no slack in the bearing at all and just the smallest amount of pre-load enough to cause some slight drag so that the handle bars fall under their own weight side to side but not too quickly.  Of course there is a special BMW tool and torque values to observe that a BMW shop would use. I think most people don't do it that way and have no wobble problems.

Here's a procedure on how to do it although I hesitate to post this link because it's a lengthy all encompassing article.

http://bmwmotorcycletech.info/frontforks.htm

and another one

http://w6rec.com/duane/bmw/wobbles.htm

[montmil]

79er,

Place the bike on center stand with the front wheel off the ground.

Slowly turn the handlebars full lock, left to right, back n' forth. Do you feel any notchiness -if that's a word?- in the steering? Any gritty feeling could indicate worn out steering head bearings that may have become brinneled.

As Barry noted, if the bars are falling off center with some force, the head bearings could be too loose due to wear or maladjustment by a PO. An inspection, fresh grease and an adjustment may help.

Is the front wheel balanced? Tire pressure correct? Fork fluid levels per spec?

And a final thought... Is the rear swingarm properly torqued? That may be a reach

Monte

[clonmore1]

Great links Barry,

Could be useful in the near future as the rebuild starts on the way up!

Thanks

[79beem]

Ahem!

Low tire pressure was the cause.
I know, I know, check it every ride.
Lesson learnt.

[nhmaf]

With my BT45 tires on, I once had a wobble that would come and go like clockwork between 40 - 45 MPH.   After a couple miles on the road I turned around and went back home to the garage.  The cause was that the front tire pressure was down to about 24 PSI (I normally run it at 35 PSI).   A little air, and problem solved.  Always check, especially if you haven't riden the bike in a few weeks' time!

[steve hawkins]

Also, when tyres get worn they can also show this by a little wobble of the handle bars, especially whist decelerating.

I had a BMW K100RS that used to let me know when the rear tyre had had it, by giving me a gentle little 'shimmy' when decelerating down though 30 mph or so.

New boots and she was happy again.  But you have to ride your bike a lot to learn to speak her language : )

Tyres would always be the first place to look for errant handling.  Its also the easiest to check.  Condition and pressures.

Rev. Light

[Barry]

I'll 2nd steve's comments on tires and it's not always obvious which one is to blame. I learnt something when a new front tire didn't cure a wobble but a new rear tire did.