there's nothing in the 4th edition rules stating that bikers cannot use 2 single-handed weapons for the +1A bonus.
so unless there's a special rule within your codex that says otherwise, any model with 2 single-handed weapons gets the +1A!
cheers!
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"Who are you to question my methods?! A 'Puritan' is simply a coward who hides behind a veil of pretended faith and denounces his loyal brother as a traitor out of simple jealousy!"
- Inquisitor Odion |