Shimano Tourney (TY21 series) exploded view - #3445 February 2012
Derailer Adjustment
The B-Tension Screw Is Not Long Enough. Why? Solutions? – Brainy Biker
Rear derailleur B-screw does not affect upward limit on guide cog. Cog slams into the cassette with any small drop or bounce on a rock or root. It's very loud, and I
Top-bike Tourney Rear Derailleur RD-TY300 6/7 Speed SGS Direct Mount : Amazon.co.uk: Sports & Outdoors