low gears jumping advice please

[oldgreyandslow]

i changed the rear cassette to a 12-27 from a 12-25 now in the lowest (largest cogs) 2-3 gears it seems to jump a bit and bertainly doesn't run true. It's OK on the smaller cogs. I tried the barrel adjuster but no luck.

 

[stumpy66]

How any miles has the chain done and is it a long cage or short cage deraileur, is there enough capacity to take the extra teeth of the cassette

 

[lpretro1]

May need to adjust B-screw to accommodate bigger sprocket

 

[daddyshambles]

May need to adjust B-screw to accommodate bigger sprocket

good call dude