Loss of power momentarily???

[totalmoto]

I had a fuel pump relay go out on me. Bike is running nice 99% of the time. The exception is when I run 1st gear up to about 5 or 6k and shift to second. It won't accelerate until I pull the clutch in and rev it , then release the clutch and it will regain power. Any ideas? Bike is a 99 with 12k on it.
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[Tomo]

You say it won't accelarate - what does happen instead?

Does something similar happen when you take off from a standing start with some revs on?