Mongoose bicycle, replace handlebar stem
 

It looks like it has a non-standard bicycle stem without a long bolt and a wedge. It only has a short with a one and a half inch Allen bolt that goes down to a star washer that looks like if you tighten it it will expand the washer. Unfortunately I can't post a picture because I'm a newbie

It sounds like you are describing an “Ahead” type stem. Are there sideways clamp bolts just above the headset?

Yes. I figured it out I think. All I have to do is remove the old one with the side bolts and install one that's longer from Amazon.

Correct, but it also controls your headset bearing adjustment. So find out how you do that as well.

I wouldn't recommend getting anything from Amazon but your local shop can help you so you don't run into issues. They can make sure you get the correct sizes and get it adjusted properly.

you'll want to watch this vid... and OVER-tightening is easy to do, but has BAD results..


over-tightening the clamp screws can and may cause the stem to CRACK, so be careful, and if you have a small torque wrench, now is the time to use it.

AND.. make darn sure any SEALS get back in the correct orientation and positions, or you'll be hating life until the new parts arrive.
been there, done it.