There's a flush brass cap on the stock set-up, easy to see with a mirror. When I did mine, I removed the carb, but left the throttle cables attached (seemed easiest). You'll have to loosen the two carb clamps to twist the carb so you can drill a small hole in the plug (1/8" or thereabouts). Remember that there are two hoses on the right side of the carb that fit tightly, they'll resist letting the carb twist and it seems the throttle cables also hit the frame backbone. That's why I pulled the carb loose. Once you have the pilot hole drilled, use a small self tapping screw to pull the plug. It isn't in there very tight, mine twisted a little when the bit grabbed. Go gently, the fuel screw is right under the plug, 3/16" maybe.
If you want to remove the throttle cable bracket, those two screws were the tightest I've found on the DR, almost 'red Loctite' tight. If I didn't have an impact driver, they weren't coming out. Have two allen heads to replace them, for future ease of disassembly.
Here's where to look: