I am one of several owners on this site of 90's yamaha 600 twin motors that are/were getting poor mileage. It was frustrating to me because when new the sled got 12 mpg. Tried a lot of fixes over the years but none had any affect on mpg. Finally heard of something new(to me) and it sounded like what I needed. It was the main nozzles mentioned by 74Nitro. I'm back to 11 mpg and a happy camper. They are scarce so hurry if you'll need them. Thanks to 74Nitro- now the needle on the fuel gauge doesn't move as fast as the one on the speedo.