Looks like you got a magnum mkll not magnum II
Choke slide needs to be clipped into lever/rod or it will fall down and bike won’t idle,
You push rod down to start cold, most all puchs with bing carbs after they sit enough to get cold like overnight for a few hours and still need the choke for a second or two.
The rod comes up when you turn throttle and after that you sill may need to pull by hand last 1/16 of if it sticks/stays down a bit,
You only need to have choke down for a few seconds after start then rev throttle to pull up,
Start when hot by full open throttle and release
Full throttle pull on some stock throttles can be 21mm if carb is only 14mm and idle screws adjusted for 2 mm open then throttle only will have to pull 12mm so only turning 1/2-3/4 the way,
Ya you could be lean at 62jet similar setups I run with performance pipe go 68 to 72 but make sure you have a 14mm intake,
Here is my 2 speed magnum that has stock cylinder most parts and pipe,
If your magnum don’t run somewhere close to the magnum in this crappy video,
Your bike actually should pull and be faster than one in video considering you have an expensive pipe and or maybe a kit on your bike, mine don’t (and it was hard for me to have a good run holding a old crap phone with one hand and riding one handed) then if not then your magnum MKII is not running good add or running right,
Mine starts easy too when cold basically one or two kicks with the choke on just for a second then soon as it comes to life I blip the throttle releasing/pulling the choke up,