Starting Problem

[Archrms]

Recently changed the plugs with the exact brand and heat range. The original plugs were heavily fouled by either oil or rich carb setting, however, the engine ran fine. I had a friend look at carbs (dual quads), and he said both primary fuel bowls were set too high and the secondaries were too low. He then proceeded to adjust the floats in both carbs. It was late when we finished, and it rained the next day, so today was the first day to fire it up and take a ride. It fired up on the first try, and idled roughly for a minute or so (no choke). It then quit and would not restart.

I checked all the plugs and cleaned them to be sure they weren't the issue, (they were still cleaner than the ones I took out originally). It won't catch completely, and occassionally has a small backfire through the carb with some flame if I keep cranking it and pump the pedal.

Nothing was changed but the plugs and the float levels, and now it will not start. The plugs are exactly the same, so they should not be the problem. Is there anything that I am missing and should be checking? Could changing the float levels cause this severe of a problem? It ran better with the fouled plugs.