Call allin with overpair fairly early?

[flettl2]

Poker Stars $5 +$0.50 18 ppl, about 1/2 hr in.. blinds 25/50

Seat 1: BB (1735 in chips)
Seat 3: UTG (2260 in chips)
Seat 4: UTG + 1 (3520 in chips)
Seat 6: MP (3780 in chips)
Seat 7: CO (985 in chips)
Seat 8: BTN (1165 in chips)
Seat 9: Hero SB (1835 in chips)

Hero dealt Ks Kh.
MP limps in, Hero makes it 200 total, BB calls, MP folds.
Flop: 4h Jh Ts (2 players, pot: 450)
Hero bets 350, BB raises 1150 to 1500 (leaving himself with 35).
Hero?

BB has been playing loose passive, limping in pots, calling flop and turn sometimes, then folding. But again I've only been playing with him for about 20 min.