My 1973 CB450 has a weird shifting issue. When I shift into 3rd gear everything is fine unless I give it a lot of throttle. It then feels like it is skipping or jumping. If I don't grab a lot of throttle it is OK, if I shift into 4th not an issue. Could this be related to any of the parts on the clutch side or does it sound internal? I do not have any experience with shifting issues.