Reposted from Tech Help: Handlebars on 2024 Husqvarna TC125 shaking in the air

5th gear jumps?

probably an out of balance tire, or the weight of your rim lock.

These bikes aren't meant for that kind of speed over jumps, but if your track is like that, you could try removing the rim lock or replacing it with a different tire to see if it goes away.

The only time i have encountered this problem on 3rd gear jumps is when my wheels had built up mud/dirt on them, which throws them out of balance.   But if you are feeling it on the ground in 5th gear, you definely have a balance problem.   If your rim is in fact true, i would try a different tire and possibly a different rim lock.   The rim lock does throw a dirt bike tire slightly out of balance, but you shouldn't feel it much over a 3rd gear jump.

Have the wheel balanced with tire weights and that should fix the problem.

Bad tire? Maybe hit something square messed up the bead internally throwing it off? 

Have you put it on a stand and spin the front wheel as fast as you can. That would take every other moving part out of the equation and you would know for sure that it is a front wheel/tire issue.

also check the rear wheel while you are at it.

y’all balance your tires? i thought we just slapped these puppies on and ran em.

Bad wheel bearing?  Bent disc?  

Balance beads work well in dirt bike tires and you don't have to worry about the stick on or spoke weights falling off while riding.

https://a.co/d/8HgmsdJ

No, but I race moto so my bike has probably never even been in 5th gear.

Going with this, especially the latter

If nothing is bent (disc) it’s probably a wheel out of balance. Could be front or rear, a bad (out of round?) tire or tube could be the cause. Those balance weights posted earlier are sweet, we used to wrap solder on the spokes and it was ugly. It makes a difference though, I used to do the wheels on my KX500s and it helped a lot, the faster you go, the more it helps. 

Post the fix, it’s good to know how these things go.

Relax your death grip.

Let go and let Jesus take the wheel

Surprised nobody is saying this… is the front wheel correctly installed in the forks. If it’s not, it’s quite easy for it to be misaligned, or loose in the forks and wobble around.

Put the bike on the stand and grab the back tire, shake it back and forth while watching the bars. Your problem may be the rear.

Do you have 2 rimlocks on your back wheel? I’ve seen guys install both locks right next to each other and throw a wheel way out of balance.

Tap the front brake while pushing the bike to check for the click of the Triple clamp bearings being loose. 

Are Front wheel bearings shot?

Check the handlebar clamp bolts (under top clamp) to make sure they are tight.

Amen! 

Do tou have a buddy that you can swap wheels with to narrow down where the issue is coming from?

Also, for those above, 5th gear jumps are definitely not unheard of on a 6 speed 125.  

We're just going to go around in circles with everyone posting solutions to a problem nobody really understands. We have people suggesting wheel bearings, brake rotors, wheel weights (really? On a mx bike?), bead locks, tires, tubes and frigging balance beads... I'm going to assume if you took the front wheel to a dealership to check for trueness, we should probably start low and slow with suggestions. 

Can you be a little more specific on the "shaking" you're experiencing? When you say "We have done everything we could think of", what exactly is that? Is it like a head shake? Is it a vibration in the bars? What exactly do you mean by "shaking"? That term could mean many different things to different people. A little more specificity would go a long way in helping to diagnose the issue. 

He could be shaking in fear at the speed in 5th gear!

When you're feeling the shaking are you on pavement/hard packed dirt? 

Can you borrow someone else's front wheel to see if it still happens?  That will atleast help narrow it down.

Only bike i've ever had do this was bc the front rim was bent. Also never heard of balancing a tire on a dirt bike in 25 years of riding/racing. 

Remove spoke wraps….

Motocross dirt bikes don’t need to be balanced, but balancing dual sport wheels is very common and highly recommended. There’s a reason they sell them…