How do I remove the wedge of the previous stem?

On another note, the new stem came with a metal "sleeve" that I couldn't get to fit into the frame. I just took it out and didn't bother using it. Maybe that means something to someone?

I pushed the new handlebar stem in as far as it would go. It's quite high, but looks quite cool. If it isn't dangerous to leave it the way it is, I might leave it that way.



With regards to the gear problem (that I mentioned briefly), I converted the bike into a single speed. I've had this bike since I was about 16 and i'm now 23! In all this time, i've been using it on top gear and I don't think i've ever changed it down. I decided to take the plunge and convert it, and boy am I glad I did! The handlebars look so much cleaner and there aren't cables anywhere. It's also nice to have customised it since it now feels like "my" bike. My sister stole it for a year, and when it came back it had been in a car accident =(

Also, i'm a complete newbie at doing anything with bikes. I've only ever changed the wheels of a bike before, so if you can think of a rookie mistake, i'm probably making it.

These are the questions i'd like answered:

1). How do I remove the wedge of my previous handlebars?
2). If it is indeed the wedge that's stuck in there, is it dangerous to leave it in and put the handlebars over it?
3). Out of curiosity, what MTB frame would you recommend for under £100? I'm in the UK, so European websites only i'm afraid.

(P.S: is this a good frame?)

Thanks for any responses.

EDIT: ARGH! This post is going to have so many mixed messages! I just googled "wedge" and it looks like it's the triangular bit that is attached to the screw thread in the stem. This is most definitely out!

Also, I can see right down the hole to the wheels. The sides seem smooth, and I can't see anything blocking the handlebars.