basically B310 is only called 120Y in few countries.. in USA 120Y is B210

anyway, the engine will shiver due to icing of the carb. once the engine compartment warms up, everything's ok...

you can try be cold start the engine for a couple of minutes, then off the engine... touch the carb and compared to the manifold... you'll feel the manifold is sloght warm, while the carb is cold... kinda like beer cold...

or you can do what i do... water injection :D
since mine's a manual spray type of water injection... during cold start, when the engine starts to shiver, i'll give it slight throttle (still shiver) and a few squirt of water ;)... that will smoothen it up a bit. Use full when driving during cold mornings and no time to warm up the engine