Twist Grip to Thumb Shift on a Townie
I have a rather old and previously abused Townie. From what I can tell the bike was produced in 2007 or 2008. I picked the bike up because I like the old frame with the intergrated frame bosses at the fork tube and the seat post.
The twist shifter on the bike was quite old and weathered so I thought I would replace it with a Shimano 7 speed thumb shifter. I got a new shifting cable and housing, I feel I have the rear derailleur tuned as the bike shifts well going up the rear cogs from 7th gear to the top 34 tooth cog. The issue is, it does not seem to want to shift from the top cog back down the cassette to the smallest cog with any consistency.
As I mensioned, the bike has lacked TLC in the past.
I'm wondering if I might have to change out the rear derailleur for a new one.
Has anyone made this modification before, and what if anything am I missing..