Not firing on four cyclinders when warmed up - 2007 Aprilia ETV 1000 Caponord

did you check the float in your carb?

You mean without taking it to a shop for repairs, or at least some diagnosing? Check for spark on all four cylinders. If two do not have a spark, the problem is in your ignition system. Possibly the ignition coil for the two not working.
If all four spark plug wires do have spark, it could be a fueling problem to the cylinders not firing, or it could be an internal mechanical problem in the engine. Then you would need professional help.
Google or watch a vid on you-tube for how to check for spark, if you are not sure.

Sounds odd but the connection to the injector it'sself may be to blame. If the injector fires at all no matter mhat wire it's connected too the injector is good. all the injectors fire at the same time when the bike is warming up and only change after the coolant temperture senser says to the computer that the engine is warmed up. If your shur connecting the #3 injector connector wire to the # 4 injector and connecting the other as well and all the cyclinders run, ( for sure) Just leave it that way and ride it and see if the fuel mileage or performance suffers or not if not just leave it that way but if the injector driver is damaged then the injectors need to be OHM checked and they sould all be the same. If the #4 injector is less OHM's then the others change it as it will damage the computer as it may already have. If they OHM out all the same just leave it alone with the plugs switched as leave it as a job well done.

Clean the gas tank out and the carb bad gas

If you need further help, I’m available over the phone at https://www.6ya.com/expert/brandon_79b580f5a99c4386

This could be all sorts of things..probably not the fuel system (it is VERY reliable, unless someone starts tinkering with it). From you broad description it could well be an ignition fault. I take it it gets lumpy as it warms up, so (in order of cost) replace the plugs (insulation breakdown), the plug leads (buy one long one and move it round the system). If you are loosing water, you may have a gasket gone.

I would have to say that I think it's not miss fireing.
It could be the coil for those 2 cyclinders. It could be in the carbs. When you cleaned the carbs did you remove them from the engine and dismantel them completly? Clean every parts and blow out all the air and fuel ports. Did you seperate the carbs from each other? If you did the carbs will need to be synced again. Good Luck.

if the engine is front to back then Yes, you are correct.

no 1 front left hand side ,engine rotates clockwise ,10ª might be too much for unleaded fuel 95octane i would go for 6/8 degrees unless you are putting in a lead substitute .firing order 153624

I WOULD GO FOR THE FUEL INJECTOR ON CYCLNDER 2...IF YOU NEED MORE HELP GET BACK TO ME!!!

Subaru engines (including Legacy and engines of many other automobiles, GM, etc.) have returned to so-called wasted spark ignition systems since advent of the electronic distributor-less ignition (having been used historically in early engines with magneto ignitions). With this approach, the ignition systems are less expensive and usually quite reliable. At the same time, however, a shorted spark plug (cracked or carbon clogged, etc.) (or bad ignition spark plug wire) grounds both the ignition spark and the false spark being used. This means that it also grounds the corresponding respective ignition spark of the other 180 degree out of phase cylinder (that uses the same the same coil because the spark current is connected to the spark plugs of two cylinders). Since such a defect allows more current to flow in the spark coil to two plugs when the resistance of the spark plug gap disappears due to a cracked plug, etc, it seems likely to hasten coil burn out if the spark plug/plug wire defect is not corrected before installing the new spark coil.

To explain further, wasted spark means that when a cylinder is ready to fire, it gets a spark to its spark plug while part of the spark (from the same coil and current) as a sort of copy is also sent to another cyclinder at the same time but when the piston in that cylinder is exhausting its ignited gases 180 degrees out of phase from when its spark is needed. When the second cylinder is ready to fire and receives its "spark, the first cyclinder the also receivesa "wasted" spark "copy" of the one needed by the second cylinder. Economy is achieved in manufacture because otherwise electronics would have to turn on and off four different spark coils to distribute four different sparks as needed to the four cylinders. With wasted sparks (which are cheap), because the spark current of one coil is connected (internally in the ignition coil unit) to two cylinders that are in the same position but 180 degrees out of phase in firing, the system can turn on and off two spark coils twice as fast with half the electronics and fire two cylinders that are 180 degrees out of phase. A four cylinder engine thus uses only two coils, a six cylinder engine, three coils, etc., in a wasted spark system.