My buddy has a 600 Bandit streetbike and he is having some problems. Here's the background. He rode it for a year from new, then he put it in storage for a year. He used stabilizer in the fuel and filled the case with oil. When he got back he drained the fuel anyway, then cleaned both carbs really well. He also made sure the air cleaner was clean. Here are the symptoms -- when he revs it from idle it spikes high in RPMs but returns to idle very slowly like it wants to keep revving. It makes it very difficult in 1st and 2nd gears. Everything is stock. Please help.