Chris,
I had the devil of a problem with my 230 for two years until I did all the mods and suggestions from these forums.
Change earth lead position
Iridium spark plugs
1.2 mm drill out jet
Different brand solenoid
Larger battery
Because I did most of these at the same time, it was impossible to tell which fixed the problem, however I think the drill out, larger battery and Iridium plugs were the main fixits.
Incedently I have NOT used the choke once since.
Phil.