Ok, so I'm trying to get my daughter's '99 Savage running, and I have a major problem with fuel in the airbox.

This is a California bike so it has an evaporation system.  (Although, maybe they all do).

So I went through the steps I saw in another post as follow:  1) Swapped out the petcock for the Raptor version.  Same problem.  2) Swapped out the carb.  Same problem.  (The old carb had dried gas to the point that the float was stuck permanently.)

What was strange is that after I got everything back together (before adding gas to the tank), I rolled the engine over for the first time and a large amount of gas AGAIN, showed up the air box.

I finally deduced that perhaps there was gas remaining in the charcoal canister below the air box.  But not sure.  There was a drain hose below the airbox and I removed the plug and a pint of gas came out.

At this point I figured I was home free!  No gas remaining in the system!  Yayyyyyyy!

However, as soon as I added gas to the tank and started the engine, I got a boat load of gas in the airbox again.

Anybody got a clue?

Don't start the bike until you change the oil and oil filter and the air filter if needed. What happened was the stock petcock failed ,gas from the tank drained down the vacuum line into the carb where it runs into the motor crankcase or out the mouth of the carb into the air box or both. end of story ,but something we've see many times.

You replaced the float but it still needs to be checked for the proper height or flooding could happen again . You should be able to open the oil filler cap and if fuel is present , you'll smell it.  be sure to replace the drain plug on the bottom of the air box before running the motor ,as that drain is between the filter and the carb and will suck in unfiltered (dirty) air and cause damage over time.

As others have suggested.....you need to look at the oil level window and see if your oil level is "too full" - as the crankcase oil is likely diluted with gasoline.  Every time you start the bike, the overfull crankcase is blowing gasoline diluted oil out the breather tube and into the airbox.