How can you tell the year model of a Yamaha YZ 250 dirt bike serial number 1W3-001435?

you should look on the fram of the bike right in front of the gas tand on the side and it should tell u. 1977 250 YZ250D 1W3-000101 6520 NOTE: This Is The First Year Of The Plastic Tank, Used On All Bikes Except The YZ80, YZ100. It Was Also A Completely Different Frame/Monoshock/Engine Design For The 125/250/400 Models. Bob (Hurricane) Hannah Raced An Almost Completely Stock YZ250D In His Sucessful 1977 Season. From this very helpful YZ identification web site. Hope this helps http://craigmac215.tripod.com/yzmodels.htm

Go here to look up serial numbers http://www.motoverse.com/tools/vin/yamaha.asp