300ex only half rev..???

i have a 1998 honda 300ex and just put in new rings. has a big bore kit in it. timing is right on and no odd noise when idle. fires right up and sounds great again but for some reason it will only rev half throttle and then revs out. all power is gone at that point. need some help i have tried going one tooth back on the timing and goin on tooth ahead and does not change,.any if would be great.