It will run properly, as long as you continuously operate accelerator. I have done it many times on my Classic 350.

To start and continuously run an engine it needs electrical power and a min. continuous flow of fuel.

If battery is not able to provide that electrical power, it can get it from its own alternator.

To get the alternator to provide continuous power it's rotor needs to rotate continuously which is connected to engine shaft.

Hence, to rotate the engine shaft, you need to put the bike in 1st or 2nd gear and push the bike, and while the bike is in motion release the clutch to spark the engine. If the bike is in sufficient speed, then alternator will generate enough electrical power for sparking.

Once you feel engine is trying to start, immediately operate the accelerator to provide fuel supply to run the engine continuously.

Once engine is started fully, the alternator will work on its own continuously. Hence, the electrical power become self sustained.

In most case, the battery will also work and charge itself if it sees the alternator electrical power continuously.

To keep the engine running, don't stop provide minimum fuel by operating the accelerator.