i have a 95 kawsaki zx7 with a freshly rebuilt motor. it has sat at the shop i bought it from for a while and with me for about 3months. it has only been ridin for 1hour in 3months. in first gear when i hit about 5500rpm till about 8000rpm it studders a bit then hits hard again. anyone have any ideas what it may be? any help would be great thanks.