engine cranks, backfires, but doesn't start

[thelonewolf]

 My rv wont start  the carb and plugs fuel filter oil  distributor cap  was all replaced.   It sounds like it wants to starts but just back fires. And smoke  comes out  carb.   Do  any one else  have sugestion. Why it wont start and yes it has gas.   Was running before engine  is good so is tranny. Any helpful  tips would be great  ty

[TerryH]

Easiest first check is to see if you've crossed a couple of plug wires, followed by point gap. Then check your timing - should be checked after any tune up.
If it is a problem with your new carb could be a little more involved and there are many here far more experienced than I with carbs.
If it is a carb issue you'll have to identify the make and model.
Terry

[Rickf1985]

The fact that it backfires and you say the cap and wires were replaced that would be the first place I would look. Check to make sure you have number one wire in the right spot on the cap and then go over the firing order from there. If that does not solve the problem let us know. I would pull out number one plug and crank it over till it pops your finger out of the hole and then bring the timing mark up to top dead center and take the cap off just to verify that the rotor is pointing at number one wire. If it is one or two holes off you lost a timing chain. If it is on the other side of the distributor then the either the distributor was taken out and put back 180 degrees out or the wires were put back wrong.