How do i decode yamaha yz 125 engin id number

Hi, do you have any idea at all? 80's, 90's ? I have a 1978 YZ 125, and i can tell that from the engine number, all 1978 yz 125 were stamped 2K6----------
You can find out with a bit of research online, using your engine number. Also, look on the steering stem of the bike for a year date stamp.
Failing all that, make a phone call to your nearest yamaha dealer, and tell them the engine number, they can look it up and tell you what year it iwas built.
One more solution, go to a website like bikepics.com find YZ 125, and look for the model that resembles yours, they have photos of all models, from begining to most current.
So, really the only way to find out is from the engine or frame number.

Go to this site and enter your ENTIRE VIN number:

http://www.motoverse.com/tools/vin/yamaha.asp