back in the day Yamaha's clutch set up for these pipes was very poor and did not work well, they needed a high engagement but they did not sell springs stiff enough to do it, we machined the covers and spiders to use Polaris springs that worked for a time but the covers eventually broke, the best set up I used was a cat 9 tower clutch with adjustable weights and a red EPI spring spin at 8300, do not lean the mid any it will burn down!!! 92 or better octane and would run boost as well as we all know the quality of gas now days.