Its like the wording between "space marines" and "space marine sargents", space marine sargents can't have lascannons.
A "biker" is not a "biker sargent" (who like tactical marines has his own set of upgrade options), even if our grammatical ven diagrams always assumed they were. I got called on it, realised my glitch and apologised to a few folks who I'd actually won against with them.
You dig?

Tactically this fubared up my min max allotment of weaponry and added to my reasons I gave up on them.(should be ok for you if your taking 6 though just put them on other fellows

killmaimburn wrote:Common RAW view is that the sargent can't take the grenade launcher (meaning I was cheating a fair amount of time I used them)

I never realised that.
(Just checked the codex and it is consistent with how I would interpret other units, for example, I wouldnt put the Plasma Gun on the Sgt in a normal Biker Squad)

Poo.

~ Tim

Scout bike sgt entry says he may replace his bolt pistol with... and he may take melta bombs and/or locator beacon.
Codex says up to 3 bikers may replace their bike's twin-linked boltguns with grenade launcher.
But...isn't the sgt a biker and isn't his bike equipped with twin-linked boltguns, so can't he replace it with a grenade launcher?
I think he can.

Can the Sgt in a normal biker squad take the Plasma Gun then? (that says "biker" also...)

~ Tim

Looks like he can, a biker can replace his pistol for a plasma gun, but not a combi-weapon. Only the biker sgt can do that.

EDIT: on second look, doesn't look like he can (either regular or scout) permissive ruleset, the sgt would only be allowed to replace his equipment with items the codex allows him to. Mea culpa!