Tried to help my neighbor out w/his early 2000 250 Bear Tracker. Backfired when he tried to start it/hard and mostly impossible to start. I/we removed the carb. dissasembled it and soaked in my super carb cleaner, blew out all the ports, etc. Now, it starts right up, but is running rich as I see black smoke fm exhaust and notice plug is sooty. I must not know the needle or jet adjustment and need some help. Outside the carb I can adjust the idle and another adjustment in front of the bowl. Is there a pre-setting on any jets "inside" the bowl? Sure could use some help here. Another thing I noticed and had him order was the rubber connector fm the carb to the engine...pretty bad shape and thought it might be sucking air?

 

If it was Sucking in AIR it Would Over-Rev.

My guss is When you Blow out the Carb , Thier Must have been a Small rubber in the Needle Seat and That Had Gone with it . Or The Rubber is Missing off the End of the Needle.

Needle & Seat is the Little pump Part In Most Carbs.

Or You have Bent the Float Prong where the Needle Spring Go`s.

UP is Rich Down is Lean. As the With the Float you can change the Fuel Consumption.

Now i wouldent know the settings of your Mixture , as i have not one of them bikes.
But default on most Apps , is : 1+ 1/4 turn on low , 1 +1/2 on High and if a Air Jet 3/4 turn out. And it should run. than Adjust from thier.