The Dodge County Sheriff’s Office continues to investigate two serious injury motorcycle crashes over the weekend. The Sheriff’s Office says 45 year old Donald Rennhack from Brandon received a serious head injury when he was ejected from his motorcycle on a county highway in the town of Lowell Saturday afternoon. He was not wearing a helmet. About an hour and a half later 21 year old Hunter Frankenstien of Beaver Dam was flown by helicopter to a hospital with serious injuries after he failed to negotiate a curve on Redwood Road near Jersey Road and was ejected. He was traveling with a group of four motorcycles at the time of the crash.