Hey guys new here (sorta) and need some help.
I have a late 90s early 00s Cannondale R800 with full 105 components. I tore the bike down and rebuilt it in 06 with new cables, paint, brake pads and rebuilt and repacked the bottom bracket. I also installed a quill stem adapter so I could put a clamp on stem on it to get the angle and length I wanted.
After everything was all set and running perfect my idiot brother dropped it, a whopping 2 rides into the new set up. When it fell over it landed on the derailleur side and bent the hanger, which after attempts to get it straight by a local shop it ended up snapping mid way up a hill, not fun. I replaced the now cracked hanger with a new one, and readjusted the cable and shifting.
A few rides in I noticed that the chain would jump down 2-3 cogs when I would freewheel (back pedal) and when I pedaled forward it would return to the normal cog. Now this only occurs when in the highest 2 cogs but it is still quite annoying. I have adjusted the cable at both ends to no avail and after 2 years of dealing with this I want to get it fixed.
I'd like to do it myself so any tips as to the cause and how to fix it would be greatly appreciated. I have a feeling the rear derailleur is slightly tweeked but not sure how to align it or check it for that matter.