I've got a Shimano trigger shifter on an 8 speed derailleur. It only allows me to use 4 of my 8 gears. I can adjust the derailleur so that it is the top 4 or the bottom 4, but the shifter just won't click through the rest. It clicks 3 times and then acts like the rest of the gears don't exist.
I've tried adjusting the derailleur. Seems to work fine. I can even get the bike to shift by pulling the cable manually.
I've sprayed a ton of WD-40 into the shifter. That definitely improved the shifting speed and smoothness, but no affect on clicking through the rest of the gears.
Does anyone know what is happening or to fix it? When I opened up the shifter case, it does not look easy to mess with...
Thanks for the help.