Seems previous owner used epoxy to stop a leak.
TTR250 Raid (4GY)
Decompressor blanking plug.
If it isn't leaking then maybe best to leave it alone. Else see here
Brian
Exeter, Devon, UKhttp://www.ttr250.com - The one and only dedicated TTR250 FAQ!
TIP: For easy viewing bookmark the "Recent Posts" view - http://ttr250.activeboard.com/p/recent/