Clean the needle with carburetor cleaner and a soft toothbrush or cloth.
Soak a cotton swab with cleaner and buff the seat and rim. Once both parts are clean, the needle should function properly.
In the CB450 set of carburetors we used for the photos, the end of the carb float needle that sits in the notch in the float was corroded. The photo below shows the carb needle we removed next to a new needle.
So in the CB450SC carbs, the needle moved in the seat easily, but was no longer hooked to the float. The float moving up and down no longer controlled the needle movement and therefore the needle no longer controlled the fuel supply.
If your needle is damaged in this or some other way, it needs to be replaced.
You can purchase a needle and seat together as an assembly, but sometimes, especially with older bikes, all you can get is the needle.
If you do have to replace the float valve assembly. K&L Supply has a
float valve assembly available for your 1996 DR200SE. It is on page 223
of their 2009 catalog. Needle Valve Assembly, OEM Suzuki part number
13370-44500; K&L part number 18-4666.
K & L Supply does not sell directly to consumers. The majority of dealers and motorcycle repair shops carry K&L products. You should have no trouble locating a dealer. If you do run into a problem, you can call them, 408-727-6767 to locate a dealer near you.
After all repairs have been completed, remember to change the motor oil and filter.
Be sure to check the airbox for fuel puddling and empty drains on the airbox bottom.
Also, it is a good idea to be sure that on any carb float bowls that are equipped with a drain nipple, that they have the hoses going from the bowl nipple to the ground. This prevents any fuel that is trying to escape, to reach the ground. Avoiding any electrical components or hot pipes along the way.