I have no idea

[GZ250]

This normally happens with my GZ when I try to start after a long gap and especially when the bike sits under open skies. Now after cleaning the carb if you have messed something I can't cay but it is a non-issue if you are just starting after sometime and the bike was in good running condition when it was left.

Start with an overnight or a couple of hrs charging to the battery. That is the main thing. Over time the batter looses the real juice that it cannot give the push to the engine to roll over. Leave the gas On-Res-Pri switch to Prime for a minute so everything gets wet with gas. Use choke. It will start.

If you have old gas add gas additive to it. Get fresh gas and add additive to it. It will clean everything from the bike's stomach.