Against an unkonwn I would assume that his range on the river is Tx, Jx apart from AJ which most people would 3bet or c/r and straight draws. The K on the river only improves either KQ, Q9 or KJ. I think if you bet the river it's going to have to be a shove, I think he'll fold out all his Tx  and some of his worse Jx hands and call everything else. The more I look at it the more borderline I think it is. Does anyone know how to do an EV calculation of this? I am right to think that you do +1140* the percentage of his given range that is made up of all his Tx and J2, J3 and J4 combinations. Then + (880 + 1140)* the percentage of his range made up of J7-9. Then -(880+1140)* the percentage of his range made up of KJ, Q9, KQ. 

I think you should jam, I wouldn't expect him to fold any Jx and might call worse hands too, and I agree that if he makes a straight on the river there's a decent chance he'll lead the river. I don't think betting smaller than allin will increase his calling freq with weak pairs high enough to compensate for all the times he stacks off Jx.@longjohn it looks like you're trying to calculate our equity in the entire pot rather than the EV of our river bet. It'd be much easier to simply look at our equity against his river calling range and check if that number is > 50% because our equity in the 1140 pot depends on his entire range to get to the river, rather than the part of his range that actually calls our bet. We'll realize our exact equity in the 1140 pot against his river range when we check behind and showdown so we're only concerned about whether or not we should risk our last 880 against his river calling range. 

Ok so what would you recon is his calling range do you think he's folding any of his Jx?

Well since we have a Q it makes it less likely, he has something like KQ/Q9 actually.

 You should have looked for the hands that he would have called oop preflop.Hands that we want to get some value from are: Jx, Tx. We don't know much about his calling range. Some terrible players would call preflop with J4o, J2s, T6o+, T4s+. Let's assume that we would call preflop with J8o+ J7s+, T8o+, T7s+. I think that most players would call your river jam only with better hands (you might even get him to fold AJ) or with Jx. Your betsizing is large, which makes his river range stronger. Unless he's a huge fish and would call you widely preflop and on the river i wouldnt shove the river. I think that jamming this river is terrible.600 river bet also looks quite strongly. He probably wont call you with Tx. He might call you with Jx but might fold it as well. There are  a few better hands that might call you.I would bet here about 250. Now we might get called by Tx and probably by all Jx. Some stubborn players might even look you up with 3x, 6x, Ahigh. If he likes slowplaying a hands like 2 pair, sets, or checkraising on the river (some improved hands: 2 pair with a king, straight) then checking back seems to be fine.