A forum for owners of Yamaha TTR250 trail and enduro bikes!

Hi to all!!,

im sort of new to 250 biking so this is the first time im changing sprockets on my own few days back i brought 2 sprockets off amazon. 

http://www.amazon.com/gp/product/B001AVU0SA/ref=oh_o00_s00_i00_details

and 

http://www.amazon.com/gp/product/B001AVXA64/ref=oh_o00_s00_i01_details

and now thy have arrived. chain was looking good so i didnt order that.i was planing to buy a renthal after sometime when the budget is recoveres. And when i checked it agaist the chain i already have its totally different and the bike has 19-57 gearing. well its not suprising that srilankans are good at carving metel :P so the owner before me might have made them from a workshop. and when i checked the chain also have 2 joins :O and 135 links

anyway my question is how can i check wether the chain is 520? and what chain should i use and how many links? whats the difference between renthal r3 and r1? and how to check wether 520 will fit the new sprockets?