The 1931 Junior TT Race was run at a very fast pace by Jimmie Simpson riding for Norton who completed the first lap in 30 minutes and 49 seconds and was 6 second ahead of fellow Norton team-mate Stanley Woods in 2nd place and 18 seconds ahead of Freddie Hicks in 3rd place riding an AJS motor-cycle. Although, Jimmie Simpson was able to hold on to the lead for the next 5 lap, he was slowed by having to refuel every two laps because of carburetor problems. Fellow, Norton team-mate, Tim Hunt recovered from a slow first lap with a loose plug-lead to set the fastest lap on lap 4 of 30 minutes and 5 seconds an average race speed of 75.27 mph (121.14 km/h) and steadlly moves-up the leaderboard. Further, carburetor problems causes Jimmie Simpson to drops off the leaderboard and eventually finishes in 8th place. This allows the 1931 Junior TT Race to be won by Tim Hunt riding for Norton, in 3 hours 34 minutes and 21 seconds, at an average race speed of 73.94 mph (118.99 km/h), from Norton team-mates Jimmie Guthrie, and Ernie Nott riding a Rudge motor-cycle.
The 1931 Lightweight TT was dominated by the works Rudge motor-cycles and the race was lap 1 by Ernie Nott by 45 seconds from Rudge team-mates, H. G. Tyrell Smith and Graham Walker in 3rd place. By lap 6, Ernie Nott had a lead of 4 minutes over the rest of the field, until on the last lap he slid of just below the Mountain Mile and finished in 4th place steadying a damaged push-rod with his hand. This provided a first and only TT Race win for Graham Walker riding a Rudge at an average race speed of 68.98 mph (111.01 km/h).
The highly anticipated 1931 Senior TT Race which was again set to be dominated by Rudge and Norton motor-cycles. However, it proved to dominated again by Norton and Jimmie Simpson and Jimmie Guthrie, this time Guthrie led on lap 1 by 1 second from Jimmie Simpson and Norton team-mate Stanley Woods by 17 seconds in 3rd place. On lap 3, the 1931 Senior TT Race produced the first 80 mph (130 km/h) lap by Jimmie Simpson on a Norton motor-cycle in 28 minutes and 1 seconds an average speed of 80.82 mph (130.07 km/h). Despite taking over the lead from Guthrie, Jimmie Simpson crashed on lap 4 at Ballaugh Bridge and the bike ending-up in the river. Despite re-taking the lead, Jimmie Guthrie slips-off at the Governor's Bridge on lap 5, but contuines to finish in 2nd place at an average speed of 77.34 mph (124.47 km/h). Fellow Norton team-mate Stanley Woods finishes in 3rd place with a glove in the petrol-tank filler. The fast paced and incident packed 1931 Senior TT Race provided Tim Hunt with a popular Junior/Senior double win in 3 hours, 23 minutes and 28 seconds for the 7 lap (264.11 mile) race at an average race speed of 77.90 mph (125.37 km/h). The winner of the 1929 Junior Race, Freddie Hicks crashed on lap 5 at Union Mills and was killed.
At Sulby during practice, Jack Williams riding a Raleigh motor-cycle is timed at 100 mph (160 km/h) and Percy Hunt riding for Norton is timed at 101 mph (163 km/h).
During practice, Wal Handley slips off his F.N. motor-cycle at the Gooseneck.
During the 1931 Junior TT Race, H. G. Tyrell Smith riding for Rudge retired on lap 3 running-out of petrol. At Ballacraine, Otto Steinfeller retired with gearbox failure. On lap 5, Ted Mellors riding a New Imperial motor-cycle and F.A.Renier both crash at Glen Helen. Both continue and Ted Mellors finishes in 10th place and Renier in 16th place.
On the first lap of the 1931 Senior TT Race, Wal Handley riding for the Belgium motor-cycle firm of F.N. slips off at the Quarterbride and retires. At Keppel Gate on lap 3 of the 1931 Senior TT Race, R. F. Parkinson riding a NSU motor-cycle hits a bank and 3 spectators are slightly injured.