Yamaha RT180

Looks like the RT-180 was made from 1990 - 1998 per this page http://zedder.com/msg9.htm#models

and this page http://www.merrittmotorcyclesalvage.com/yamahamodelcodes.htm If you can find the VIN stamped on the steering head and it matches one of these, that will tell you (RT180A would be a 1990, for example)

Look up Google Images for each individual year until you find a match; i.e. search google images for 1990 Yamaha RT180 and see if the colors match up. If not, try 1991, etc... Some bikes come in more than one color per year.

This is supposedly a '93