Welcome to Librarium Online!
While reading the Bike rules on page 53 of the BBB the other day I noticed a couple of things I had not been aware of.
1) Bike riders may only fire one weapon each. So, if a model has a hand carried melta gun in addition to the standard bike mounted twin-linked bolters, he can only choose to fire one or the other.
2) Bike mounted rapid fire weapons can fire once at max range, even if the bike moves. No surpise here...
3) Rapid fire and heavy weapons may fire, and the bike can still charge into close combat. So, if you don't mind Gets Hot rolls on expensive bikes, you can still rapid fire with hand held plasma guns (and not fire the bike mounted twin linked bolters), and still charge into close combat.
Interesting... Plasma Guns CAN rapid fire, AND the bikes may still CC. Plasma riders combined with a Techmarines signum (reroll a miss) might be an option to consider. Also, note that regular pistols used as CC weapons will never be fired, unless you want to give up use of the bike mounted bolters. A plasma pistol might still be an option though...
Then, in the Space Marine codex, page 37.
1) Normal Bikes don't get pistols or CC weapons standard any more. But they still get one attack per thier stat line, (running people over, or using a high speed fist?)
2) Veteran Sarges and Independent Chracters can have weapons from the armory, and thier is no restrictions as to having two CC weapons.
So normal bikes get no CC weapons, and leaders can have two.