I'm only familiar with mikunis from working on bikes but here goes. The excess fuel symptom needs to be fixed first, all the other issues, dieselling, hard start etc will have to be dealt with after you get the fuel under control. I don"t know what kind of fpr you have but they are very unreliable. In the end I always end up getting a fuel pump the does the good psi. My experience is that if I get the fpr set so that there is no extra fuel about at idle it runs lean at extended high rpm. So,if you want set the fpr up to a pressure that does not push past the valves. If that is not possible and you are sure the psi is low enough ("T" in a pressure gage) you need new float valves. SOme of your othere symptoms ( hard start etc) kind of sound like the fuel is syphoning back towards the fuel tank, simple test park it on a steep slope nose down and see if it persits, or see if your fuel tank drains out through the carbs

!!!!!CAREFULL!!!!!!!!!