cheapie wal mart stem keeps coming loose with my mx bars any ideas?

[heartlandcruisers]

well i have discovered a problem that is beginning to irk me a lot with ym recent build.
I have a huffy cruiser I just built up form old parts and it rides good except one kind of major issue.. the handlebars keep moving forward.
no matter how much I tighten them they still manage to move and I have to keep adjusting the bolts.
this is becoming a major safety concern because I ride this bike hard and it has caused a few spills
now where I can just lick my wounds and laugh it off I am concerned if I let my 12 year old daughter ride this and the bars shift she could get hurt pretty bad.
any ideas where to look for issues/ or what I can do? or are the mx bars not compatible with a cheapie stem.
any info would be appreciated I don't really want to pu tan expensive stem on a bike im just going to beat the bejesus out of.
thanks
Sean
p.s. here is the stem I am using

 

[Shackleford]

My first thought was to drill the stem and throw a bolt in there since its a wally world off spring. Depends if you care about the bars tho?

Maybe some small amounts of lock tite on the bolt threads?

the bolts slowly coming loose during riding?

 

[KJV]

Can see from pic...you need
to tighten the 4 Allen screws.

 

[heartlandcruisers]

Well I do not wanna ruin the bars their in really good shape
I will try to tighten the Allen bolts more but they don't wanna turn,anymore nut I'm sure I can get them to move

 

[alistair clark]

I would look to see if it tight enough, then I would look at the center of the bars and see if the manufacture had put in deep enough sirrations on handle bars. Then last thing would be replace the stem and then the bars themselves if they still move.

 

[roadwarrior]

Drill out the bottom plate of the stem, get longer bolts, use flat washer then lock washer along with some threadlocker red.

 

[Joe Monstermaker]

When we were kids and had that problem, we used to put a little piece of leather in the stem around the bar.

 

[user 135]

Do those bars have a bulge(25.4mm) in the middle or are they straight(22.2mm) across in the clamp area?

That stem is meant to clamp down on (22.2mm or 7/8") bars.

 

[pebblewurm]

Cut a shim from a piece of beer can, wrap it around the contact area and tighten the heck out of the 4 allen screws. Use LocTite if you have some. Take a look at the screws and threads in the stem to see if they are messed up- new and better quality screws could solve the problem.

 

[us56456712]

The bolts don't appear to be equally tightened, some are run in deeper and some appear to be out more. This can cause unequal pressure with part of the bar looser, but you still can't tighten it enough in this situation, all 4 should be equally tight. You could try loosening all of them and rotate your tightening until they are all in about the same and then work around, tighten one a little and go across diagonally to the one opposite and continue until you can't get it tighter. This might help?

 

[heartlandcruisers]

Do those bars have a bulge(25.4mm) in the middle or are they straight(22.2mm) across in the clamp area?

That stem is meant to clamp down on (22.2mm or 7/8") bars.

yes that does seem to be a problem there is a slight bulge in bars themselves I think you are correct on that being the problem for now

 

[heartlandcruisers]

The bolts don't appear to be equally tightened, some are run in deeper and some appear to be out more. This can cause unequal pressure with part of the bar looser, but you still can't tighten it enough in this situation, all 4 should be equally tight. You could try loosening all of them and rotate your tightening until they are all in about the same and then work around, tighten one a little and go across diagonally to the one opposite and continue until you can't get it tighter. This might help?

yes I tried that and still loose I decided to swap it out for now until I can find a better stem.

 

[heartlandcruisers]

well I decided to swap the stem out with another one until I can buy a decent one the new stem does work better but still loose I am thinking the problem is the stems aren't designed for these kind of bars or the screws are not long enough to accompany the handlebars nonetheless I put this on the back burner for now until I can find a good stem to work with these bars
more updates soon
sean

 

[KJV]

Try wrapping ducktape around the bars,in area under stem. Then tighten back down.

 

[user 135]

yes that does seem to be a problem there is a slight bulge in bars themselves I think you are correct on that being the problem for now

One like this should work if your clamp area on the bars is 25.4mm. http://www.ebay.com/itm/Mongoose-BM...017?pt=LH_DefaultDomain_0&hash=item4638d54671

Take a picture of the bars off the bike and we can for sure let you know.

 

[Nagant]

Making shims from a aluminum can and wrapping them around the clamped area of the bars usually fixes the problem even if your using incorrect sized bars and stems.

 

[Bicycle808]

There's a whole lot of excellent advice on here, but we need to find out more info before we can figure out the best course of action. However, I agree with the folks above who speculated that your bars are 1" at the bulge, and the stem is designed for 7/8" diameter bars. If that's the case, no amount of shimming, hardware changes, or careful tightening will help you. Measure the bar, and make sure it matcnes the stem you decide to use. From there, you can use some/all of the other suggestions if need-be.

 

[heartlandcruisers]

There's a whole lot of excellent advice on here, but we need to find out more info before we can figure out the best course of action. However, I agree with the folks above who speculated that your bars are 1" at the bulge, and the stem is designed for 7/8" diameter bars. If that's the case, no amount of shimming, hardware changes, or careful tightening will help you. Measure the bar, and make sure it matcnes the stem you decide to use. From there, you can use some/all of the other suggestions if need-be.

actually you are spot on bicycle808 I measured the bars and it is a 1 inch at the bulge and the stem does not tighten enough to stop it from moving.
thanks for all the advice but I just decided to swap the stem out with a different one and it seems to be working now.
sean

 

[KJV]

I'm running 1" bars on 7/8 stem, type your using. Never had problem. of course I know how to draw down evenly.

 

[Bicycle808]

actually you are spot on bicycle808 I measured the bars and it is a 1 inch at the bulge and the stem does not tighten enough to stop it from moving.
thanks for all the advice but I just decided to swap the stem out with a different one and it seems to be working now.
sean

I'm running 1" bars on 7/8 stem, type your using. Never had problem. of course I know how to draw down evenly.