1200rpm-1800rpm backfire when cold?

So I think I may need my distributor serviced? Converted to hot spark( I know should be petronix) runs great. Had issue with timing. How accurate are the degree marks on the casting? Ran like crap at the recommended 6 degrees made it more like 12 degrees runs sweet. Except it will want to back fire upon easy acceleration. only when its cold and everything hasn't gotten completely warm. It i run it for 20min no problem. Or do I have a carb problem with the accelerator pump? If I pump it its ok up out of the hole. It I try to cuise just after engine temp is achieved at 1500 rpm it will try to stall? Any thoughts? Thanks!

What engine? If you have Solex carbs or carb, these are non-choked carbs and the engine takes a while to warm up. By the sound of your post, it may just be a still not warmed up engine or may be tuned a little lean.