I don't know if anyone else has experienced this issue, but in about 3 years time my 06 YZ 125 has twice leaked coolant into the transmission. As we know, the "air gap" design of the seals on the water pump shaft prevent coolant entry the usual way (bad seals on pump shaft), so the only other possibility I can see is that the right side case gasket fails at that circular coolant passage that feeds the water pump. This time I put it back together with some Permatex #2 coated around that passage area. So far so good, but it has only been two rides. I'll update as time goes on, as now I will go back to my usual 15 hour oil change schedule. I would be interested to know if anyone else has had these problems, and what steps you have take to solve it.