I just bought a 1989 Honda NX250. I changed the oil, added coolant and put seafoam gas treatment in the gas tank. a day later, the engine is not running right at all. When giving throttle the engine bogs and loses power. I am now having problem starting the bike, even when fully choked. It was running better before i did all of this. Also, friend told me when i got the bike it needed a valve adjustment. What could be the problem?