if it fits firm.. then its fine and it's not a rotor issue.
the rotor has a lil spring contact on it that touches the inside top of the cap.
as long as the rotor is not rettely loose ont he shaft.. it's not the rotor.
1, pull plugs and look at them.. if they are ashen white. you may be lean.
try this. tug on choke a bit when trying to accelerate. if it works better.. enrich the mainjet.
other things to look for.. make sure she is fireing on all cyls. when running above idle and sounding rough.. pull 1 plug wire and repalce at a time.. see if they all make a difference..and make about the same difference. if you find one that makes no difference.. or less difference.. that plug may not be fireing.. or that cyl may have an issue.. like stuck or burnt valve.s
a comp check may tell you more.
post back for details..e tc..