2nd pair on the pocket on flop

It's ok to just call and first wait for the flop. Actually he did 3bet from the button and against the button-range you have either a 50-50 situation against overcards like AQ AJ AK or you're behind against a better pocketpair. Situation would be different if you'd openraised from CO and he'd 3bet from the button. Then you should rather cap but even though SB is in the pot, your advantage is quite marginal. let's check it out


       Equity     Win     Tie
MP2    41.29%  40.43%   0.87% { 77+, ATs+, KQs, AJo+ }
MP3    24.28%  23.56%   0.72% { TT-44, AQs-A6s, K7s+, Q8s+, J8s+, T8s+, 97s+, 87s, AQo-ATo, KTo+, QTo+, JTo }
CO     34.43%  33.92%   0.51% { 99 }

I calculated a quite loose range for SB but obviously. the tighter his range becomes, the less Equity you have. You see that you're just a minimum over average eQuity and impact and Equity-change is tremendous for small pocketpairs. More frequent you see overcards and you're almost drawind dead whereas if you have AJ, you have less overcards and more outs to draw to. Thus you should , especially out of position, just call with medium pocketpairs and wait for the flop and if the flop comes 246 you can checkraise for value.. I would actually fold the Turn here because you just beat AQ with a flushdraw and SB calls again. It's just too unlikely you're still ahead and if so, BU has many outs against you but most of his combinations have got you beat already. AK AJ 77 TT QQ etc.

As played you should checkraise the River. If BU did have AQ you won't get another bet anyways but it seems as if he's got something that he's gonna be betting again. Fold Turn and as played: Checkraise River!