Honda em5000sx only runs with choke on. It runs rough with black smoke coming out of exhaust. Cleaned carb with carb cleaner. Can gas cap vent be a problem or is it just adjustment?

If the plugs are ok and your engine is not smoking after starting and running ..Sounds like either of three things..all with the carburetor .First the carb has a adjustment screw for air/gas mixture on the side if the carb where it attaches to the engine..try this start the engine and at about half throttle..now adjust the screw clockwise until the engine starts to miss and bogg down then back the other way until it starts missing and bogging again. Then slowly adjust back and forth until you hear the engine run the smoothest..give it more throttle if it starts to run rough do the same procedure until you get the results you want..if it is the mixture problem this will take care of it..if this doesn't it it may be your fuel jet in the bowl dirty or the blow float sticking..if you are not familiar with carbs best to have a professional look at it..you can drop the bowl by removing the bottom bowl and clean it out...check to see if the float easly moves up and down..replace the bowl and go from there..worse scenario new or rebuilt carb...good luck..

check to see if the choke cable comes in contact with any linkage on gear selector sounds like a choke issue

You say you cleaned the carb. If you did that by spraying cleaner in through the choke, that's good, but it doesn't get to the root of the problem. The problem is getting the gas into the carb. Try this. drain the gas. Put a small amount of carb cleaner and gas in the tank (about 1:1) Start it up, but don't run it dry. Let it sit for an hour. Then start it up and run the tank dry. Then try just a little gas to see if that fixed it. If not, repeat. Good luck Al K

GX340 engine always works best with complete carb kit that at least contains main jet, needle valve, main nozzle and orings. It is hard to clean varnish/crud from carb and soaking may make it worse. Kit is not expensive. Check ebay, less than $10. Before you change any parts make sure that your cap is venting properly. Many California gas caps (tall chrome gas cap) may cause fuel lock. Also check that muffler is not restricted with carbon. Good luck

sometimes they are stubborne,I use stranded electrical wire to send through jets,just make sure when blowing into an orfus that it comes out somewhere hope this helps

01 Sounds like it is running out of fuel because it wants you to choke it to get more fuel.
02 Might have a restriction in a fuel line. Disconnect at carb and see if there is a good flow of fuel.
03 Loosen the fuel tank cap and see if the same thing happens. Cap might not be venting.
04 Any black smoke from muffler?

possible check vacume hoses if its hookup properlly

Sounds like your Carb needs to be cleaned. The easiest way to do that is to remove the fuel lines attached to the carb (note where they go first). Then pull the plastic caps off the the carb adjustment screws (discard if you'd like). Then turn the screws clockwise while counting the number of full turns (that way you can put them back at the factory settings). Take both screws out. Then take a can of carb cleaner and spray into each hole along with the inlet of the carb (this is where the air comes into the carb). Also while you are there you may as well clean the filter with soap and water.
Good luck!

the carb is located under the aircleaner it sounds like the mower is being fan at full throttle this on some mowers applies the choke try ajusting the throttle to full then slightly back to open choke.