Hello, I have a 1984 Yamaha Phazer 480 that will start right up and idile fine. The problem is when at WOT it only goes about 50MPH and won’t rev over 5,000 RPM. However when stopped then going straight to WOT it will hit about 6,500 RPM then quickly bog back down to 5,000. I have the fuel air screw set at 1.5 turns out as it calls for in the manual. It has a new top end new belt and the carbs have been cleaned. Does anyone have any suggestions?