Fuel coming out of the rear of the carbs

take off complete cover

carbs need to be cleaned and set

there is a small port on top of the second carb on the right, that goes to the small port on the fuel petcock mounted to the tank. The main fuel supply (larger port on tank) goes to the bottom fuel supply rail with the only carb port on that rail. The upper two ports between #1 & #2 carb and between #3 & #4 carbs are vents and those hoses get plumbed down under the air cleaner, careful not to pinch the vent hoses or the bowls will not fill up with gas. This is the same for an automatic petcock or a manual one.

The first thing I would do is to stick in a new spark plug even if the shop says all is well. It will only cost a couple of bucks and now you KNOW the plug isn't the problem. If the shop tested the ignition system and all is okay, have them check the compression on the bad cylinder. Bad valves in that cylinder could be the problem. If the compression is okay, another possibility is a plugged main jet or gas is not getting into the carb due to a float being stuck closed or fuel line obstruction. Also, but less likely, is water filling the float bowl. Condensation inside the gas tank can make it into a carb. Bikes do not run well with water in the gas.

Check the mouting locations and carb boot/seals for cracks. this appears to be a vaccum leak nad the previous area's mentioned should be checked as well as throttle position.

the jetting/ jets are fittings inside of the carburators that allow onlky a certian amount of fuel to burn so the motorcycle does not flood itself out by having to much or to little fuel

May I suggest a trip to your local library. Cycle repair books should be in 646 stacks of reference.

On the one that has two hoses does it still have an "Off" position? Usually petcocks that have two hoses, one goes to the carb vacuum, and the other is for a fuel supply for the engine. That way it only allows fuel to flow when the engine is running. I have found these to be a poor design and can often leak and allow fuel to run into the engine if your carbs are acting up. If the replacement only has one hose, then it will work fine, just be sure to cap off the vacuum port on the carb.

You will have two lines coming from the petcock on the bottom of the gas tank. the small one goes to the front of the number one carb, and the larger one plugs onto the fuel rail in the middle of the 4 carbs on the back. The lines that run between the 1 and 2 carbs and the 3and 4 carbs are just overflow lines, so they don't hook on anywhere else.

clean the carbs