Help Bevel gear is fixing to come off

Hi there, Im Joe from Texas and I have an 80 cc boy go fast kit mounted on a beach cruiser. I have upgraded just about everything and just when I thought I had it right I start to hear a squeaking noise at all speeds. I first heard it when i was doing about 35 so I backed it down some. The squeaking noise was heard at any speed. I figured I would go home and grease up the clutch gears and thats when I found out the bevel gear looks like its gonna come off. I looked up several threads on this problem but have not been able to find exactly the information I need on taking it off and installing a new one and also what are the proper tools, If some one out there has input on this it would be greatly appreciated. Also I would like to add that I have a brand new 80 cc spare engine I can take parts off.

Yeah I saw that link but I was hoping I didnt have to tear down whole engine to do it. Im starting to think My little China Girl is about to retire.

I tried to remove the screw but the tire turns with the counter clock wise turn I give it using a large screw driver. I try to hold the tire but is still seems stuck. I read threads where they say you have to use an impact screw driver but I dont have one or a compressor.

I also forgot to ask, Do I need to replace any parts or are you saying I can just hammer it back in after taking off the screw. I am also forgot to add that its the little gear coming that looks like its coming off.

I used hammer and flat head screw driver to loosen the screw and then I used a socket that fit perfectly in the hole where the screw was. I pounded it in with a hammer and it worked. I noticed the key was still in place and looking intact. I took it for a 30 mile ride and took off the cover when I got home. I was surprized to see every thing was still in place. It worked and thanks for the replies.