Okay, I'm Stumped. I need some ideas about what's wrong with my bike.?

This may sound as daft as it gets, but it cold be fuel starvation. Check the breather hole in the tank filler cap it could be partially blocked and the 1st pot in the fuel line getting most of the fuel. I had this intermittently and it just never clicked until out one day needed gas took the tank bag off and hissssss, as air went in to the tank. So hope it's this simple for you.

Backfiring through the carbs or throttle bodies is usually a symptom of too lean fuel mix. If you're sure it's misfiring on one cylinder only, I'd suspect the injector. You say they put it on the scope; did they hook an oscilloscope up to the fuel injectors? That's the most surefire way to find a bad one. A dirty one can dribble, causing a too rich mixture while one with a faulty electrical winding will run lean or unevenly. Keep in mind that a bad injector may only misfire at certain throttle openings or temperatures. If they don't have an oscilloscope, see if you can swap the injectors and see if the front cylinder now runs bad.

If you suspect both cylinders are backfiring through the TBs, you might check the fuel pump pressure for a weak pump or a bad pressure regulator that's causing the pressure to be too low. That will cause lean running as well.

If they didn't check the fuel pressure and injectors, don't feel too bad. It's easier to find a problem when it won't run at all that when it runs, but badly.

Also check the Fuel pump strainer in the tank if it has a punp in the tank. Im not really familiar with the bike, but somthing could be clogging up the filter screen. It a little thought about item that can get restrictive. Its also pretty easy to check operation of the map sensor and TP sensors that both if not operating properly can cause a lean conditon at certain times. Does it have a Coolant Temp sensor possibly bad?. It has a lot of influence in the dynamic fuel delivery also. They dont always throw a code either on most vehicles unles they are dead nutz. Same with the IAT sensor. Check or have them check that for operation. There are certain voltage values for sea level operation that should be present. This is all assuming that there may be moew than one cylinder "missing", because as I read this, it may not necessarily be a dead mis. When the bike is not being fuel right, it can feel like a miss or like a dead cylinder, when in fact its all of the cylinders that are lacking power because of the lean or rich condition.

Normally a flat spot happens

1. When air fuel mixture is lean, for which you will have to check the inlet manifold and its gaskets/o rings for proper sealing

2. Check the compression of all cylinders if good, you will have to check the valve timing

3. If it was of CB. points ignition check the points gap and condenser, If electronic open the coils and check for correct resistance.

4.Check whether the exhaust port for blocking with carbon, for this open the connection at cylinder head and inspect and if necessary start the engine check the engine raise.

5.Check the fuel pump out put and condition of the suction filter

6. Check the performance of ignition coil and its out put volts.

Might be time for a valve job (not valve adjustment).

After 8 years, there should be enough mileage on the engine for carbon build up to prevent the valves from sealing closed.

Reduced performance, lowered MPG and backfiring, are results of leaking valves.

Perform a cylinder leak down test to check for leaking valves.

A lot of good thoughts above.

One thing that comes to mind - the throttle position sensor.

A faulty signal from the sensor will cause all the problems listed - lean running, power loss, backfiring...

Had that problem in a cage... high highway miles, the throttle sensor was badly worn in one spot.

My first thought was float bowl adjustment, but then you said, "fuel injection". That means there's a computer somewhere doing the thinking for you. It believes that it doesn't have enough air to match the required amount of fuel. Some things to check:

1. Air Filter: Did it disintegrate and get sucked into the airbox?

Try removing the filter and riding. Does it fix it? Replacing it with a thin napkin. Does that help?

2. EFI box: Try swapping it with another unit. Rule out that the box didn't crap out.

3. Valve clearances: Maybe there's a valve stuck. Compression & Leakdown may detect.

Spitting out of the throttle body eh? Cam chain or can chain tensioner, Burnt valve, Broken valve spring. Worn exhaust cam lobe, Collapsed tappet, Unmistakeably a valve related problem.

clean the carb it could be pluged up often happens if air cleaner to dirty or you dirt bike a lot.

check the coils too