[SixForty]

Preflop - a lot of people will tell you 86s is a little bit thin, but I do it a lot. It depends entirely on game conditions, you really like loose passive, and since you mention that the game is playing pretty loose preflop, I call.

Flop - open ended straight draw with a backdoor flush draw and two overcards. Man - that's a fantastic flop for you. Let's look at your outs.

Four 7's will give you the nuts, so all four are solid clean outs.
Four 2's will give you the second nuts. True, you can lose to 76, and you may chop with any other 6. But this is counteracted by the fact that you still have outs to beat either of those hands with a higher straight, and that on a 2345 board, any and all Aces will pay you off, possibly even raising so you can 3-bet and fleece them big time. So I count the 2's as four solid outs.
The backdoor flush is worth 1.5 outs. True it's not to the nuts, so if we want to discount it to only 1 out, that's fine with me.

You also have 2 overcards which, although dubious, may actually be outs here. So let's count them as "something". Basically, that means they are more higher than "nothing"

If we add all that up, we've got a hand worth 9 outs plus "something" - basically, we have more than 9 outs.

So a 9+ out hand, against 4 opponents, I'll win more than 35% of the time - I want lots of money going in on the flop if possible. So now I look at the best way to trap opponents. Given the position of the preflop raiser, there is one opponent between you and him if you bet, but there are two opponents between him and you if you checkraise. So my plan here is to check, and hope that the preflop raiser bets it, and if even one (hopefully both) of UTG and UTG+1 call, then I checkraise. If both fold, then I'm just calling.

Since none of that happened...

Turn - You are now getting 14.66-2 on a call. You've still got 6 clean straight outs, and 2 that may be tainted by the backdoor flush, but are probably good. But since you only need 6 outs at least to continue getting those odds, a call is necessary. Even if CO 3-bets, Button caps, and UTG+1 folds (which is worst case scenario) you'll be getting effectively 19.66-4, which is about 4.9-1 to call. If all your straight outs are clean (ie, no one has a [img]/images/graemlins/heart.gif[/img] flush draw) then those odds alone are enough to call.

Also, given the action so far, if you do hit, you can count on implied odds on the river. Button is not folding this hand, and CO probably isn't either. So you can count on probably 2 bets on the river.

So go ahead and call the turn.