YZ125 is referring to a Yamaha motorcycle with a two stroke engine designed for motorcross riding. The Yamaha YZ125 weights 189 pounds dry and 208 pounds wet.
There is a serial number stamped on the engine (e.g. E112E-****) that may help. Maybe you can contact Yamaha with that number for an age? Or you can just search yz125 on bikepics.com and just find the year that looks like yours.
2000
1lx-00 is a Yamaha yz 125 -86
02 YZ125
32:1
1990
1994.
with stock up to 85mph
Websites like ebay and bike find are places to purchase a Yamaha YZ125. Also local classifieds in the newspaper or even on craigslist might have it to buy.
torque specs air fuel mixture screw on a yz125 2003
It it's year 2000