When you wack the throttle on the trail, the rpm's jump to 8000,(track spinning?) then fall to 7000 very quickly. In the deep snow is only pulls 7000ish. Both clutches are freshened up with all new parts and springs. A reliable source says it's the secondary not back shifting, or the exhaust valve is not opening properly. I believe the secondary is ok, but I will pull it apart just to double check the spring has been wound 1/3 of a turn. I am wondering the best way to check the powervalve? And any other ideas? Thanks.