You had a feeling the choke is supposed to be connected?? The choke is in the side of the left carb and the choke tube is on the opposite side of the choke it is a small black tube that connects the carbs. You need a clymers manual.
When your ready to buy some parts let me know. I have a set of holeshots that are almost new, a few billet odds and ends, and a set of blue tag fat bars with clamps.
Backfiring is normally a sign of a lean codition, did you do a leak down test to check for air leaks? What are you mods, elevation, temp, current jetting?
I have the msr shorty easy pull on mine with heavy duty clutch springs and it works great. I have an extra one if you need it pm me. Welcome to the site
Welcome to the site. Still running the stock filter, any mods to the airbox? If not I would start around 260-270 and work down from there with stock pilot jet.
No need to pull the pipes to see if they have fuel in them or drain the cases, if your pipes or cases are full of fuel you have a more serious problem. Start by checking the basics, fuel, spark.
If you find a set of jugs, i have 2 sets of pistons boths are 64.5 one set for stock stroke and the other is for a 4mill and only have a few hours on them. Pm me if you need them.