It is in the float chamber of the carburetor.
That is the main jet needle valve.
I would suspect a bad needle valve and seat in the carburetor. The float level can also be set too high. I would replace the needle valve and seat and check float level.I would suspect a bad needle valve and seat in the carburetor. The float level can also be set too high. I would replace the needle valve and seat and check float level.
Dirty or stuck open needle valve in carburetor.
On the top of the carburetor there will be a cable leading to a bottle cap looking deal unscrew that off of the carburetor and there at the bottom of what comes out you will see the needle of the needle valve. Be careful not to put it back in the wrong way, if you do the ATV either wont start or it will run WIDE open when you so start it.
Stuck floats or dirty needle valve.
what is the needle valve adjustment on a 125 DR
Your carburetor is loading up. Or your needle valve is out of place or stuck.
It very well could be, or a problem with the float. Remove the bowl off the carburetor, remove float, needle valve, and seat. Clean all parts good with carburetor cleaner. Float the float in some fuel to make sure it floats (when should not that any fuel inside of it). Put needle valve, seat, and float back on and open fuel valve a small amount, lift float up to see if it will shut fuel off, if it does reinstall bowl. If not you may have to replace the needle and seat.
Bad needle/seat valve on carb.?
Basic adjustment for small engines carburetors: Close (rotate clockwise) needle valve but do not overtighten since the coated tip may get damaged. Open (rotate counter clockwise) needle valve 1-1/4 to 1-1/2 turns. This should be ok to start the engine. Start the engine and allow to warm up for 5 minutes. Then fine tune the carburetor by SLOWLY closing the needle valve until the egine starts to stall for lack of fuel (mixture too lean). Then SLOWLY open the needle valve until engine starts to stall due to excess fuel (mixture too rich). Set the needle valve midways between the two extremes. If the carburetor has two needle valves, one is adjucted at idle and the other at half throttle.
Basic adjustment for small engines carburetors: Close (rotate clockwise) needle valve but do not overtighten since the coated tip may get damaged. Open (rotate counter clockwise) needle valve 1-1/4 to 1-1/2 turns. This should be ok to start the engine. Start the engine and allow to warm up for 5 minutes. Then fine tune the carburetor by SLOWLY closing the needle valve until the egine starts to stall for lack of fuel (mixture too lean). Then SLOWLY open the needle valve until engine starts to stall due to excess fuel (mixture too rich). Set the needle valve midways between the two extremes. If the carburetor has two needle valves, one is adjucted at idle and the other at half throttle.
Float probably stuck or has a hole in it allowing fuel to enter or Bad needle and seat valve