Motorcycle Repair: Quick increase of rpm but no acceleration., friction plates, clutch lever

Question
I have a 2000 yamaha yzf600r.  The bike has 12500 miles on it.  I just bought the bike and have knowledge of its past.  I had to have a garage replace the carburetors with used one because a previous owner tried to modify the old ones and screwed them up.  My problem is that when I try to quickly accelerate, the rpm's will jump up (say go from 5000 to 10000) but the bike does not accelerate.  There is a delayed reaction, as if the clutch is slipping.  I recently changed the oil and put in Spectro 4.  I noticed that my oil level was a little low so I added about 200-300 mililiters.  Still having the problem.  Any advice?

Answer
Hi Josh...

Hmmm.... Yeah, sounds like the clutch is slipping. I would open the clutch, pull the friction plates and measure them with a caliper... could be that the previous owner was a bit hard on the clutch and the you might need new plates. But don't overlook making sure the clutch lever freeplay is adjusted properly. Good Luck Josh... hope this helps!!

Jack