10NL - AKo runner runner 4 flush board

[Gospy]

Full Tilt Poker - No Limit Hold'em Cash Game - $0.05/$0.10 Blinds - 6 Players - (LegoPoker Hand History Converter)

SB: $6.40
BB: $7.40
UTG: $14.05
Hero (MP): $10.25
CO: $5.85
BTN: $17.20

Preflop: Hero is dealt K[img]/images/graemlins/club.gif[/img] A[img]/images/graemlins/heart.gif[/img] (6 Players)
UTG folds, <font color="red">Hero raises to $0.35</font>, CO calls $0.35, BTN calls $0.35, 2 folds

Flop: ($1.20) A[img]/images/graemlins/spade.gif[/img] 4[img]/images/graemlins/diamond.gif[/img] 2[img]/images/graemlins/spade.gif[/img] (3 Players)
<font color="red">Hero bets $1.00</font>, CO calls $1.00, BTN folds

Turn: ($3.20) 7[img]/images/graemlins/spade.gif[/img] (2 Players)
<font color="red">Hero bets $2.50</font>, CO calls $2.50

River: ($8.20) 9[img]/images/graemlins/spade.gif[/img] (2 Players)
Hero checks, <font color="red">CO bets all-in for $2.00</font>, Hero ???

Villain was running 70/30/1 through about 40 hands. I realize that it's $2 to call and I'm getting 4-1, but does he not have a spade here often enough? This play screamed spade to me. The flat call on the flop and turn made me feel like my hand was no good. Fwiw, I folded, is that a good play?