I have a 1978 Case-David Brown that 2 years ago broke crank at 45 degree angle in # 1 rod it was running 900 RPM's at the time.I had it rebuilt with new crank ,pistons all valves and seats,now 2 years later and 206 hours while brushhoging last night at 1400 rpms the new crank broke at the back edge of # 1 rod again .Any ideas,could the balancer be bad somehow and be the cause.thanks for your time