Engine bogging, can't go faster than 45mph

[superman22x]

Today, I rode home from my friends house and had some issues. I did a short run to 75mph on the way home. My bike needs almost full throttle to hold that speed. But today, a fee miles later, the bike couldnt go faster than 45mph... It bogs down. And there was a weird clicking noise coming from the engine. Anyone have any idea what it could be? A sign of valves out of adjustment?