Don't know what model dirt bike I have?

Just got an old dirt bike from a friend to re build and fix things and I need to change out the killswitch but need to make sure I have the right one but the problem is I have no idea what model dirt bike this is, all I know is its a Honda but I have no knowledge of the cc can someone help identify please?

Picture?

The engine size will be written on the bottom of the cylinder. On the frame, where the forks attach there should be a number which will tell you what the bike is.

Here's a photo of the bike! Don t know what model dirt bike I have - 1

1981 - 82 Honda XR80