just my contribution
its called a " pin dowel " they are 86 cents from riva yamaha ,
here is the link
http://216.37.204.203/Yamaha_OEM/YamahaATV...pe=13&A=208&B=4
Click that link, select your year, and model , and then go down to cooling system underneathe the engine tab. From there you can see a water pump break down aswell.
Enjoy