Jack Arnst was a cycle champion on both road and track between 1903 and 1910. He gained the fastest time in the 1903 Timaru to Christchurch road race and the Warnnambool to Melbourne race. He also gained fastest the time in the 1909 Timaru to Christchurch race, but was later disqualified for accepting pace from his brother, Dick Arnst, who had earlier pulled out of the race. Many racers were disqualified for minor infringements of the rules that year. He went on to set long distance cycling records, including the Christchurch to Dunedin in 12 hours and 21 minutes. He, and several of his brothers, became champion cyclists both on the road and track.
John "Jack" Arnst was born at Tai Tapu, Canterbury on the 3rd Feb. 1882. He was single when he signed up on the 7th January 1917, but married Agnes Archibald at the Registrar's office, Napier on the 23rd. Jan. 1917. He resided at 58 Marine Parade, Napier and was a farm manager in Waipukerau.

His parents Katherine and Herman Arnst, were both born in Hanover, Germany. They were naturalised about 1886 in Christchurch. He embarked from Wellington 21st Nov. 1917. Arriving in Liverpool on Jan. 8th 1918. Marched into Sling Camp and promoted to 2nd. Corporal.
On the 20th March left for France and on the 24th March, marched into Camp at Etaples. On the 4th. May he was posted to 12 Company in the field and Reverts to Ranks at his own request.

Private John Arnst was killed in action on the 25th. August 1918 by artillery fire, while accompanying German prisoners to a dressing station near Bapaume.