How do i replace the water pump seals,on my yamaha yz 125. 2004

SOURCE: yamaha yz 125 2001.water leak

Yes, the water seal is leaking. This is the indicator hole for the water and oil seal.
Enjoy the ride !

Jon

SOURCE: How do I change the oil seal on the water pump on

Hi,

This is a mechanical oil seal. In order to replace it, you will have to remove the right hand side engine cover. The seal is located in this cover.

If you are not an experienced mechanic then you should take your bike to a dealer.
NB use the genuine part for this bike.

Good luck

Jon

SOURCE: I have a 95 yz 125 head and 98 yz 125 bottom end.

You have a 50/50 chance that they will work okay. All the mounting holes need to line up and the cooling holes as well. Get a head gasket for the '98 and see if all lines up. Will the exhaust pipe fit the '95?

SOURCE: how do i decode yamaha yz 125 engin id number

You don't decode it. It is only a production run series number. Mororcycles are like cars in that respect. It is the frame number, AKA the "VIN number", is what carries all the information. Call a dealer with the frame number and he can tell you year, paint color, specific model and more. They may have a problem if the bike is too old. Yamaha changed to a newer code system a few years back.
Can I get a “very helpful” rating on this answer?

SOURCE: yz 125 water pump seal

GET A SMALL SCREW DIVER IN BETWEEN THE SHAFT AND SEAL PRY IT OUT WITH OUT DAMAGING THE SHAFT THEN USE A SOCKET FROM A TOOL KIT THAT FITS PERFECTLY AROUND THE EDGE OF THE NEW SEAL TO HAMMER IT BACK IN