Looking for some 120 experts. On my kids 120 the clutch is sticking. When we first start it we have to have the rear end of the ground as the track will spin instantly and if you hit the brakes to stop the track it will kill the sled.. After running it for awhile it will gradually loosen up and allow the sled to stop and idle. I've greased the heck out of it to no avail. Any ideas?