Just installed a new (from Can-Am) carb for my 2005 Outlander 400 4×4 and it fired right up after the install but would not run with less than 1/2 choke. Also replaced the spark plug at the same time I installed the carb, it was a bit fouled. After a few minutes of running it backfired thru the exhaust and now it won’t run at all. Having the exact same issues I was having with my previous carb.

From what I’ve read this is a pretty common problem, what is the cause?