[6] On 29 May 1905, Franklin competed as a private entrant at the Auto Cycle Club's trial on the Isle of Man on a "special" with a JAP V-twin engine in a Chater-Lea frame.

[9] Franklin competed with the British team in the 1906 Coupe International on another JAP special, this time with Harry Collier and his brother Charlie on Matchlesses.

[10] Discussions during the team's return from the 1906 Coupe International on the shortcomings of the organisation of the race led to the creation of the Isle of Man Tourist Trophy, which was first run the next year.

[21] Franklin, the manager of the depot, was given a position in the Indian's design department at their headquarters in Massachusetts, and left for the United States in November 1916.

[22] In June 1916, in his last race in Ireland, Franklin rode a Featherweight Model K two-stroke single, winning the prize for best performance by a motorcycle under 300 cc.

[25] Franklin certainly developed a high performance version of Charles Gustafson's Powerplus engine, to the extent that the side-valve engine became the main design used in American high-performance motorcycles, supplanting more expensive overhead valve, multiple valve, and overhead camshaft designs used earlier on racing motorcycles,[26] and persisting well beyond World War II in Class C racing in the United States.

Design improvements over Indian's larger motorcycles included a gearbox bolted to the engine and driven by helical-cut gears instead of a primary chain.

[27][28] Compared to the Powerplus-powered motorcycle it replaced, the Chief had dual camshafts, gear drive similar to that of the Scout, and a wet clutch.

[29] After designing the 1925 Indian Prince, a single-cylinder 21 cubic inches (340 cc) lightweight motorcycle which preceded Harley-Davidson's equivalent single-cylinder models by one year [30] Franklin generally approved Arthur Lemon's development of the Ace four-cylinder motorcycle design, which Indian acquired in 1927,[31] and he redesigned the Scout for 1928.

[35][36] Franklin also designed highly successful racing motors in a range of valve configurations from side-valve to overhead-valve (both 2-valve and 4-valve) and overhead-cam.

[24] In the second half of 1931 Franklin took a leave of absence from Indian to rest and recover his health, although at first he continued to work from a drawing office at his home.