double check your bulbs
tomos a3's need the head and tail/brakelights to run properly
my bullet would do the same thing
it took me a month to figure out it was a hairline split in the tailbulb
looked fine lit up but when the bike was running
the vibration would break the circuit and make it sputter
the delorto has this snorkel type tube
sometimes it gets joggled out of place
and it effects the idle and starting
it also fowls the auto choke plate btw it isnt stuck on is it?
hope i helped good luck