I have a 1986 Rebel purchased about 9 months ago. Had about 2500 miles on it at the time, and I have since added about another thousand. When I first got it, to begin riding again after an absence of decades, I found that it would occasionally slip out of second gear back to neutral. Didn't do it too often, and I thought it might be partly me being very rusty. However, it slowly seemed to be getting worse even as I improved, and now it's progressed to the point where it will slip out every second shift, which is really dangerous in traffic. For all practical purposes, it's not rideable. The shift linkage moves freely, nothing is bent, and the alignment is good going by the diagram I've seen elsewhere on the forum. The oil was changed about 300 miles ago (proper Honda oil) so I'm thinking that's not the problem. Any suggestions on what to try?