BLASTER runs great in neutral, dies soon after taking off

[STANGMAN 64]

I have an 01 Blaster that has been sitting for a couple years, got it running and seemed to run pretty well. About 3 days later it's now giving me problems. It will start and run great in neutral, and after I take off it will bog down and die, and then it will start and idle only, and only if the throttle is held all the way down. If I shut the gas off while it's idling this way, it will slowly come out of that and rev back up, but immediately bog down after I turn the gas on and take off. Any ideas?

 

[Awk08]

check .....
float height: https://www.blasterforum.com/threads/float-heights-and-how-to-adjust-them.50565/
properly clean carb while you're in there: https://www.blasterforum.com/threads/how-to-clean-your-carbureutor.254/

this can also be a symptom of a spark problem that only appears under load: unscrew plug boot, cut 1/2" from wire and replace plug boot, new NGK plug boots can be had at most auto stores for under $10, get a new B8ES plug too.
check for good ground on the black wire at the coil mount is to clean bare frame, sand it if needed.

airfilter clean and properly oiled ?
reeds good ?

since you say it has been sitting, a mouse nest in the pipe will also cause similar symptoms: pull the pipe off the cylinder and very quickly see if it helps, prolonged riding with the pipe off will fry your top end, but just a quick hit will survive. I used an electricians fish tape and shop-vac to remove the mouse debris.