i have a 1987 banshee and it coughs when you hit the gass all the way and it sputters and bogs when you shift past 4th gear and you hit it. i am not sure if i have the right reeds for everything to work right though. it had 2 stage reeds but i put stock on it because one of them broke off.(didnt mess the motor up either when it broke)

 

I would clean the carbs, if the little holes on the main nozzle get plugged it will do exactly what you are describing. It could also act like this if the jetting is off but you haven't changed anything that would have required a larger jet. We race the Blaster and I completely clean the carb after every race day just for this reason. One thing to make sure is to keep your air filter oiled. This will stop alot of the small particles from getting in. Sorry if I rambled on about something you already know, if you need anything else feel free to PM me.

 

make sure also its not sucking air.

 

Sounds like you may be running a really lean on your gas mix, idk it's been awhile since i had a banshee. another big problem could be that it's a YAMAHA. lol j/k but no really it's a yamaha dude what did you think was gonna happen?