Ever since I bought my 1980 CB250RS a few years ago, it started easily when cold and ran well but was often extremely reluctant to fire up when hot. My first assumption was that it was my technique that was at fault. Then after try every starting routine variation I could think of with no improvement, I assumed it was a fuel issue. Unfortunately I became so fixated on those ideas, that I didn't consider an electrical problem. Eventually I did what I should have done in the first place; I did some research. Among the many suggestions for causes of the problem were tappet clearance and a failing coil. I knew the tappet clearance was good so tested the coil. According to every specification I saw for primary and secondary resistance, the result I measured for secondary resistance made me wonder how the bike ever ran at all. So I replaced the 43 year old coil and the problem is solved. The bike now starts even more easily when cold and just as easily when hot. I am embarrassed that I ignored the possibility of an electrical problem for so long.
