Every morning when I wake my DRZ-400 SM up from a cold night, it will start and run just fine at first. Then, as soon as I come to the first stop sign in my neighborhood and pull the clutch in to slow down, the engine stalls, almost every time. This problem is new and just started happening in the last couple of weeks.

What might be causing this problem, and how would I go about fixing it?

Is the weather getting colder? Mine has done this a few times because the engine hasn't fully warmed up enough, just feed it a little bit of throttle if you're stopped until the engine is warm enough not to want to stall.

^ That, or clean the pilot and maybe turn the fuel screw out 1/8-1/4 turn. It's probably just not warmed up, but if it's getting cold you need to be jetting richer!

Having the idle set correctly along with the correct pilot jet and fuel screw setting helps .