Those engine arent known for eating reed valves. A single reed on each side, kinda a one of a kind engine. I'd guess you have an exhaust restriction that's causing back pressure, or the wrong pistons in it. I've owned a 650 wildcat, a 93 wildcat, and a 99 ZR 700. All had that same design and never broke a reed. pistons facing backwards? Blocking off that will kill performance. it may not even run.