Does it misfire @ 7000 rpm but no load (clutch pulled in)? If so the problem is more than likely spark related not fuel related. If it misfires with the clutch pulled in do the following

warm up the bike, then run the bike to the stumble point (with clutch pulled in).As soon as the misfires happen(give it 2-5 seconds of stumble), kill the engine (switch) and close the throtle. Quickly pull the plugs and examine them. If ONE is wet and the other dry, you found your bad cylinder. If BOTH are wet, check your plug gaps, coils, and ignitor box. If both are DRY...then the problem is fueling.

If it only misfires under load, check the fuel system/carbs.
Do you have a inline fuel filter? If so check it for flow/clogs.
Check your fuel lines for kinks/flow.
Pull the petcock off the bottom of the fuel tank, and clean the screen. You'll be amazed how dirty it gets.
If the basic's of the fuel system are good, and the bike runs fine with no load, then you've got to look into your carbs.
Are they seated properly? If you idle the bike and spray starter fluid/wd40 around the seals does the idle speed change? If so, you've got airleaks. If not, it's inside the carbs.
Check your floats (more than likely fine, as it idles fine, but never hurts), then check your needles and shims, and jets.
Record the settings here and folks can give you an idea if they are way off.

oh, and the plugs... are they black with carbon or white from heat? Are both plugs the same color? maybe one cylinder is rich, or lean compared to the other?

as a last attempt warm up the bike, then run the bike in 1st gear up to the stumble point (underload) very close to your house/driveway/garage. As soon as the misfires happen, kill the engine (switch) and close the throtle and coast to your driveway/garage. as described above Quickly pull the plugs and examine them. If ONE is wet and the other dry, you found your bad cylinder. If BOTH are wet, and you verified the ignition system, your carbs are way outta wack. If both are DRY...then the problem is fueling.