I have same bike. I have been experiencing same prob since got it up and running for 1st time in 13 yrs. My carbs are recently rebuilt, and had that reving problem when 1st turned over. After returning a few days later , now I have cylinders 1 & 3 not working. Noticed gas spewing out of both exhaust. To the best of my knowledge perhaps my metering on associated carbs is sticking. With float issues (bowl level/metering) you will experience such fuel/air issues. Because my carbs were rebuilt, its hard to accept them as an issue. I know that Yamaha used what is termed "YICS" on our bike. YICS is an induction carb system where our carbs (1-4) are connected and must have proper synchronization to maximize performance. In order to achieve this u must use a special tool man'd by Yamaha, which isolates/blocks off the carbs for sync'ng. There is knock off's in circulation. I'm gonna get one soon for around $40 and norm is $125, so I can make appropriate adjustments and go from there. GOOD LUCK.....Scott P.S. I'm in no way a bike mechanic, I have achieved this knowledge through a little research, hope it's been conveyed correctly.