i wanna buy a new chain for my 2003 blaster what size should i get.

 

How many links are in the stock one? That is the size you will need. To figure out how many just physically count them on the bike.

 

If you have the original sprocket set-up then you will need a 520 (92 link) chain. Make sure you stick with the o-ring, all the others are crap and you'll find your self changing the chain again very soon. Also, check your sprockets for damage and see how worn they are. If they are starting to become quite worn then i suggest that you change your sprockets as well because if you put a new chain on old worn sprockets then they will eat your chain up in no time. I have a 200 blaster and have only put a new chain on it twice. However the first time around i put on all new sprockets and the second time got away with only replacing the front.