I'm reposting my solution to this problem since I had searched around and hadn't found the answer. A similar thread can be found here:
http://forum.svrider.com/showthread.php?p=2327753#post2327753
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I had the same symptoms - I have a salvaged SV650 with 10k miles on it that I recently took ownership of. It was squeaking during acceleration & the sound seemed pretty consistent with the RPMs of the bike (as opposed to the speed of the wheels/chain). Hard to tell where it was coming from, but definitely from the frontish area of the bike. It seemed to get a little louder when going over bumps.
So last night I cleaned and greased the chain (which was very dirty and starting to become a red rust color), and I opened the airbox which has a small gap around the grommet of the front snorkel and a screw that was completely backed out on the rear-most screw hole. I moved the rubber grommet to fill the gap on the snorked and tightened all the screws down.
I just rode the bike this morning and the squeaking is gone. If I had more time I would have done each of the above in turn to pinpoint the cause. But due to the sound matching the RPMs, I'm betting it was the airbox that was sucking in air on acceleration underneath the air filter through that rear weak point in the seal.
Hope this helps someone that does the same search I did :rimshot:
Shady