stewdog

I recently bought a 20" flatspin freestyle bike for my 6-year old. He loves it, but to me the handlebar stem seems to be a little loose. I have tightened the nut, but I am leery about stripping it. Someone mentioned putting a small piece of inner-tube, or black tape around the stem, then tighten.

Help please. I want to be certain the bike is as safe as it can be for him.

Thanks.

BMXTRIX

Does the stem look like this:


If so do this:

1. The two hex bolts on the back of the stem: LOOSEN THEM.
2. NOW tighten the cap on top of the stem a little bit.
3. Tighten the two hex bolts on the back of the stem.

The cap on top of the stem presses the stem against the headset and tighten things up. The STEM BOLTS hold everything in place! If you tighten the cap, without loosening the stem bolts you will very quickly damage your bike or at least destroy the headset star nut.

Follow and repeat steps 1-3 above. There should be ZERO forward backward play in the handlebars/fork. But, the bars should still be able to spin from side to side easily. It may take 5-10 tries to get it perfect, and then it may be loose again after a day of riding as equipment settles, so you may have to repeat this once a day for a few days. I typically slightly overtighten - very slightly - and then things will work themselves loose after a day of riding. Not sure how much damage this causes, but it is much easier than having to repeat myself.

Keyser Soze

Your star nut in your fork steerer tube could have become loose, or dislodged.
Standing at the front of the bike with the front wheel lodged between your legs, (ultimately trapping the wheel), can you turn the handlebars? If so I would assume your starnut is loose. For this remove your stem, and peer down the tube, you should see the star nut, I'd guess you'd need a new one of these.

BMXTRIX

Oh for God's sake, what the hell are you talking about?

The star nut has ZERO to do with being able to move your handlebars side to side. You also do NOT remove your stem to work on the star nut. The star nut (see photo below) is hammered into the fork. It does not touch, or deal with the stem. When the top cap is removed from the fork and you look inside you will see the star nut inside the fork, but you do not need to remove the stem to do so.

You likely will want to remove the stem to install a new star nut if you get one, but even this is not required and is likely not a part of your problem unless you torqued down on your star nut bolt without first loosening your stem to adjust your headset.

If yo need to remove your old star nut use a long screwdriver and a hammer and knock it DOWN through the fork so it comes out the bottom of the fork.

This website has info on installing a new star nut.
https://www.bmxbasics.org/new/bmx0603.html

This is what the star nut, inside your fork looks like and those prongs on the side are somewhat delicate and prone to breaking if abused. MANY new forks are internally threaded so that you don't have to use a star nut inside of them.

Keyser Soze

Errr I don't get this.... How come you start ranting on about a star nut if you said in your first line, quote.....
The star nut has ZERO to do with being able to move your handlebars side to side

Keyser Soze

Errr I don't get this.... How come you start ranting on about a star nut if you said in your first line, .....
The star nut has ZERO to do with this

Keyser Soze

If your star nut is loose, you will not be able to fully clamp down your stem, thus having the simulation of a 'loose headset' which may equate to rocky handle bars.

BMXTRIX

That last post was better - if the star nut is broken, then it must be replaced. If it is not broken then the stem needs to be tightened if the handlebars/fork jiggle forward/backward inside the head tube.

If the handlebars are actually TWISTING from side to side then the two bolts on the back of the stem need to be tightened only. If the handlebars slip forward/backward inside the stem, then the bolts on top of the stem need to be tightened.

I went on a rant because you said "with the front wheel lodged between your legs, (ultimately trapping the wheel), can you turn the handlebars" and related that to the star nut. That has nothing to do with the star nut.

The most likely thing is:
a: The two bolts on the back of the stem are simply loose and need to be tightened because the bars actually twist side to side. OR...
b: The headset is loose and needs to be tightened as listed in my first post.

If the headset is loose, but can't be tightened as listed in my first post, then I went on to explain the star nut and the removal/installation procedures. No rant on that though, just an explanation.