I have my idle set around 900 rpm when the bike is fully warmed - which may take as much as five miles. I start with full choke and after a minute or two I push it part way in. In the city, I may leave it part way open for three or so miles. If I am on the highway, I close it as soon as I get up to speed.
As Doug, said, the Bonnies run very lean from the factory in order to pass the emission standards. I rejeted my carbs almost immediately on taking delivery. If memory serves me correctly, the Bonnies come with 110 main jets. I rejected to 112's. After adding free flowing mufflers and removing the snorkel from the air box, I ended up with 117 main jets. Dyno runs with an exhaust gas analyzer show the my air to fuel ration is darn near spot on all the way through the throttle range. I started with 123 mains and worked down until I got the air/fuel right.
The stock pilot jets are 40's. A lot of guys increased the pilots to 42. They claimed it made cold starting better and eliminating the popping on deceleration. I personally like the popping on decel, so I never changed the pilot jet size.
I have TOR's (Triumph Off Road) silencers on my other T100 with the sidecar. The main jets are 115 with these silencers. It still runs a tad lean, but not as lean as stock.
You can use the idle adjustment knob to increase the idle when the bike is cold and then decrease the idle when the bike is warm. If memory serves, the idle should be 900 rpm. I set the idle higher on the T100w/sidecar for my late wife as the sidecar increases the drag when start from a traffic light or stop sign. She liked it about 1100 rpm. I still keep it that way for me.