Handlebar wobble at 45mph

[gyraffoclops]

I've notice a peculiar thing with my bike. If I'm riding with no hands(just for fun/testing) my handlebars wobble quite violently BUT only at speeds around 45. Any speed faster than 50 no wobble, same with under 40. Weirdest thing. I'm not sure if this is a steering head bearing issue, an unbalanced front wheel issue, or something else? Has this happened to any of you guys and does anybody have any advice?? Thanks loads

 

[TwoManyXS1Bs]

I lost one friend to hi-speed wobble, almost another to same thing.
This should be taken seriously.
There are several suspension areas that individually and/or in combination that can do this.

Things to check, in order from front to back (forum folks, jump in if I missed anything)

Front tire
Front axle clamping
Front axle bearings
Front spokes
Front shocks
Weak front shock springs (sits too low, reduces rake/trail)
Triple-clamp
Head steering bearings
Frame crack around steering head
Steering geometry (modified rake/trail)
Handlebar mount bushings

Rear swingarm bushings
Crack around swingarm mounts in frame
Crack(s) in swingarm
Rear axle nut
Rear axle bearings
Rear wheel spokes
Rear tire

(Accessories)
Heavy/loose windshield/fairing
Heavy/loose rear storage box

Sorry to make such a long list, but I take this kind of thing very seriously.

 

[Tomterrific]

My 77D will do the same. I have saddlebags and just teh weight of teh bags will have the front wobble at around 40-45. A soft touch of the bars damps the wobble completely. Anything weighted on teh back?

Tires are a big cause. I've heard of several similar wobbles appearing and disappearing with a change in tires.

To add to TMXS1B's possibly over extensive list :^), rear axle alignment. Does your bike track straight with no hands on the bars or do you need to lean?

Tom

 

[5twins]

Tom, drop your forks 1/4" in the trees. That will transfer a bit more weight forward and may help. Although this sounds odd, another cause can be overly stiff rear shocks. Those hard-as-a-rock MikesXS cheapos everyone seems to be so found of buying come to mind here.

 

[jayel]

get the front wheel up in the air, grab bottom of the forks push and pull any movement in the fork bearings? does fork turn smoothly back and forth with no binding or notchesness?

 

[gyraffoclops]

Excellent advice jayel, got the front wheel up and noticed some play in the steering bearing. Tightened it up a bit and the bike wobbles way less. Still a small bit of wobble around 45mph but not noticeable unless riding no hands. The bike is a brat so I'm going to drop the forks a bit and see if that helps. Thanks for the help everyone!