back in september i had the top end redone. the mechanic put in new valves and a top end. i ran it a few times since then and it worked fine. Yesterday is when it started to mess up. i took it to the mechanic this morning and he thought it was something with the carb, but wouldnt get to it till tuesday. thats when i decided to clean it myself. could it be something with timing or valves out of adjustment?