I have a
2006 YZ250. When I fired the bike I noticed coolant leaking in a very
small amount from a small hole in the bottom of the water pump cover. It
didn't leak much but I could find no reference in the manual about
this. It never did this before. The hole looks like a small bolt or
something might have fallen out of it. What is this and can I ride the bike?
Do not try to put a bolt in the hole and do not ride the bike. The small hole between the water pump and oil seal is a weep hole. A few drips of water out of this hole is no big deal. Your 2006 YZ250 has been weeping small amounts of water out of this hole since it was brand new, but you never noticed it before.That said, if oil comes out of the hole you have a blown oil seal in the case and if water runs out of the hole you have a leaking water pump seal.