most of the older 2 strokes(1970's,80's,90's) were built to run on 87-89 octane and unless you are bumping the compression or messing with the timing you should stay with the manufacturers recommended octane. if you have the owners manual for that motor have a look and see what it says.
just remember in a 2-stroke not enough octane and you will get detonation (pre-ignition) which is hard to detect in a 2-stroke and very bad for your motor,,,,to much octane and you will start to lose power and your motor will not run as well!!
hard starting could be from iproperly adjusted choke circuit,bad compression,bad reed valves,ect,,so if you could give us a litle more info it would help