Motorcycle starts and revs but won't run?

I have a 2004 honda rebel 250, and it has a little trouble starting but i can get it started. When i rev the engine though, it starts to sound a little off and the whole bike vibrates like crazy. If i let off the clutch the bike pulls a bit, but it doesn't move if i give it throttle, like the clutch is burned out (but I think the clutch is fine).
Any suggestions as to what's wrong are highly appreciated.

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