Gents with my rebuilt BST with bone stock needle and jetting, down here in the Cape, I am getting a consistant 21 - 23 km per litre without riding like a fairy. That's very good consumption for a thumper and best I've had. My KTM640 was around 16-18 , KLR about 19-21 , and my 96 DR never got 23, but see's a regular 21....( not bad for stage 2 mod.)
I think this DR motor's cursed hot cam has a side benefit, at 5000 rpm, which is where you spend most of your time on the open road, it's sitting right bang on peak torque, where the whole dynamic plot comes together.
There is only ONE way to get a carb right, on a dyno with a properly working Lambda sensor. Get the fueling cock-on without guesswork , and for the rest of your bike's days you will enjoy best power and economy. Worth the small $ and a little effort to get this valuable data point. You have to work from the main jet backwards to form a logical chain to set up the carb good and proper.
Naturally before doing ANY of this you first validate your compression, valves, clearances, air filter, have chosen your zorst, plug gap, and all the basics ....
Also another useful observation perhaps ...the stock main of 137.5 is not lean with a Scorch pipe running a stock airbox. Definitely under full load on a cool day at the coast there is no sign of full-throttle roll-back 'perking up'. Maybe Back Then carb bikes were not set quite so radically lean I don't think.
What this implies is you can go leaner on the Reef

Geeze carbs these days .... are lean lean lean for emissions, to the point where if the bike isn't blistering hot they cough and splutter.
Even my 94DR had the mixture screw PLUGGED, and when I drilled it out I found the idle screw shut ! But I suspect my bike started life in the USA

Getting that idle set up properly was a moment of great joy for me and this bike ! : ) : ) ....no more DYING.
Lastly, most of you know I imagine, bear in mind jet kit numbers ( especially dynojet ) are not the same flow measurement as the Mikuni .... don't get lost !