Without being picky here, this is a classic symptom of running too rich. If you are too lean, you should be able to speed up by operating the choke slightly/briefly.
>> Turning off the gas at full speed caused the power to return
>> just before it died.
>Not power to return, just stopped loosing power long enough for the speed to build up...
You have to shake the float to check for gas inside it. The chances of having a big enough leak to sink it or blow bubbles are slim.
>> Maybe there is fuel in the float, affecting your fuel level.
> THe last time i had the carb off, I poured some gas in a big bowl, and held the
> float under the gas for a few minutes... didn't seem to gather any gas inside it... > and I didn't see bubbles of air escaping.
What did the plug look like and did you check it after a high speed chop or after idling a while?
> I was thinking it might be running too lean, actually, after seeing the spark plug > again.
By the way, screwing around with the oil injection could cause severe engine damage, besides confusing the symptoms. You should set it exactly as the book says.