Strange back fire developed?

[Dmulder]

My mini has developed and strange back fire and stutter. Every once in a while it sounds and feels as if it has a miss. Then it will backfire - shooting flames out of the exhaust and run very rough not wanting to get up enough speed for me to shift. It will build tons just no speed. Occasionally it will clear itself out and run properly and sometimes it doesn't.
Could this be a electronic fuel pump going bad, a carb out of adjustment, or something else entirely?
I've played with carbs before but never this type of carb on the mini.
Thanks for the help.

[MPlayle]

Flares out the exhaust is unburned fuel passing all the way out and getting ignited by the exhaust heat.

Pull the spark plugs and check for one (or more) that is wet and possibly very sooty.  That (along with the symptom of a 'miss') would tend to indicate that cylinder is not getting proper spark.  Check the rotor/cap for scorching or carbon tracing between the posts and check the connections at the spark plugs.  You may also need to replace the plug wires.

I don't think it is the fuel pump or carb.

[MiniDave]

it does sound like it's running out of gas intermittently.....take the hose off the carb and stick it in a container and turn the pump on, see how much it puts out and whether it stutters or is a smooth flow. Could also be a partially clogged fuel filter, or even a sticking float valve. The ethanol fuel does a number on the float valves sometime......causing them to stick.

MPlayle posted same time as I did.....you can get a lean backfire too.

[gr8kornholio]

Never mind all that, take it to your nearest cars and coffee or anywhere millinneal car kids are.  You could sell it for a fortune cause that's apparently how these kids think a car should run. 

[Dmulder]

So I took some time today to do some digging and checking.  Discovered that I had one plug that was very dirty. I cleaned it up and it seems to have fixed the issue. I will be doing a plug and wire switch in the very near future along with possibly going from the cap and rotor to an electronic distributor.
Thanks for the help.