I recently purchased a used Cannondale SR500 with Shimano RSX, 7X3 speed brifters. The right side (7-speed) just started missing shifts today. When I try to upshift, sometimes the lever does not engage, sometimes it does. Sometimes when I try to upshift the lever goes all the way to the left, then downshifts! The downshift lever also does not always engage and downshift and sometimes it does.
Is there anything I can do to correct this short of replacing the brifter? I searched BF and found only one somewhat related post. I have Down's manual and that's no help. I'm considering spraying WD-40 into the brifter hoping it's just gummed up, but I'll wait until I hear from the group here at BF.
If I have to replace the brifter, this will be real expensive since I will probably upgrade to a 9-speed. Any comments or help is appreciated.