I just picked up a 94 Yamaha Vmax 500. It had been sitting for a few years (with the occasional run up). Took it out a few times and noticed it bogging down when full trottle is applied. If I give it half throttle its goes good. Once accelerated at half throttle if I give it anymore it boggs down again. Ive tried all grades of gas with no noticeable difference. Any ideas?