G1 won't always climb a hill

[Tjsg1]

1983 G1 that I rebuilt over the winter. New crank seals, fuel pump, cylinder and piston. Ran good for 2 months. Still runs strong except it sometimes acts like it runs out of gas at the top of a particular hill at camp. I can sometimes rescue it with choke, and I might climb the hill 5 times before it does it. I changed all of the rubber fuel lines and blew out the metal line. New pulse line. Switched the fuel pump. If it stops, I just let it back down a couple of feet and turn it sideways and it will start and run again. Like 20 seconds. Fuel tank looks ok inside from what I can see, the pickup tube is open. Changed plug. Fuel filter etc. Cleaned carb. I'm at a loss and out of ideas. It pulls the hill strong 95% of the time.

Tj