Good time to donk the flop?

[cassette]

Have only played 35 hands with both players.
BU seems passive. 35/8 so far.
SB seems nutty at 55/40.

Felt a bit lost on both decisions.

No Limit Holdem Ring game
Blinds: $1/$2
6 players
Converter

Stack sizes:
UTG: $377.78
UTG+1: $60.11
CO: $197
Button: $270.40
SB: $231.70
Hero: $200

Pre-flop: (6 players) Hero is BB with K[img]/images/graemlins/club.gif[/img] J[img]/images/graemlins/heart.gif[/img]
3 folds, <font color="#cc0000">Button raises to $6</font>, SB calls, Hero calls.

Flop: T[img]/images/graemlins/heart.gif[/img] 8[img]/images/graemlins/spade.gif[/img] J[img]/images/graemlins/spade.gif[/img] ($18, 3 players)
SB checks, <font color="#cc0000">Hero bets $14