I have always started my engines full choke and run them till warm 1/4 to 1/2 choke. A heat riser will cause poor atomization of fuel on a cold run if stuck and will allow the intake to warm faster if working. Now if you live in the snow belt the heat riser is important for short drives.

To me the condition sounds normal, if the choke is pulled all the way out and you try to drive it its gonna buck, snort, and smell like fuel. Try 1/4 way out after start till warm. If it isn't better then worry about heat riser.

I didn't do it, no one saw me do it, you can't prove anything! "Bart Simpson"