Since it's an ABC engine, you NEVER want to run it slobbering rich. It needs to reach operating temperature and get there quick and easily for proper break-in. It might be too late for that...

Just lean it out a little until it's a pretty clean run, but still very rich with a lot of smoke coming out of the muffler. Run 3-4 tanks through it there letting it cool off COMPLETELY between them. Never run it slobbering rich, but NEVER lean or even peaked out. It could end up running great...Just get some time on it letting it cool between runs.

See if it still dies when you put the nose up after you get a couple more tanks through it, then we can start diagnosing the problem...If there still is one.

For break-in you've got the right fuel and prop, so there is nothing to worry about there.