The New Hart-Parr is probably the least understood of any of the lightweight models. There isn't much precise information known about these early tractors. In early ads for these tractors the company called these tractors their "Little Gray Tractor" This is part of the mystery for these early tractors, they were painted gray with red wheels. The New Hart-Parr's were painted gray up until the summer of 1919. At that point the familiar dark green paint was used and the red wheels continued. This color combination remained until the end of production on the lightweight tractors in 1930. Many little things are different on these tractors. The most obvious thing is the New Hart-Parr cast into the front casting just below the radiator. Also the two holes in the front casting were first made in a triangle shape and then they made them round and put the exhaust pipe out the front. The first 300 tractors built used a short exhaust pipe with the muffler sticking straight down under the engine. Some other distinct things that tell you right away that it is a New Hart-Parr are the open flyball governor, a foot brake instead of a hand brake (although some later tractors built in 1919 had a hand brake), see foot brake here, a flat bottom Madison Kipp lubricator was used and was mounted on cast iron pedestals. Some of the unique things used on the 1918 New Hart-Parr are the steering wheel, fuel tank, and front steering universal joints. These parts are hold over parts from the Hart-Parr Little Devil tractor, according to part numbers.

New Hart-Parr Specifications ENGINE: 6½ inch bore by 7 inch stroke, 750 rpm. IGNITION: High tension KW magneto. LUBRICATION: Madison Kipp force feed oiler. CARBURETOR: Schebler with Dray Kerosene Shunt. TRANSMISSION: Two speeds forward, one reverse. COOLING: Honeycomb radiator, water cooled. FRAME: One piece, cast steel. FRONT WHEELS: 28 inches diameter, 5 inch face. DRIVE WHEELS: 52 inches diameter, 10 inch face. SHIPPING WEIGHT: 5158 pounds. PLOWS PULLED: Three 14-inch plows.

The New Hart-Parr was first experimented with in 1917 and looked similar to the Waterloo Boy tractor. It had the fuel tank mounted on top of the radiator and the fan was belt driven. The final product went into production on Feburary 14, 1918 and that basic design continued until 1930. The early prototype tractor may have been labeled 12-25, but none of the early advertisements make mention of the 12-25 horsepower rating. After several months of production the horsepower rating was labeled as 15-30, referring to 15 horsepower on the drawbar and 30 horsepower on the belt pulley. Another very distinct internal difference on the New Hart-Parr is the heavy counterweights bolted to the crankshaft. After approximately building 1000 tractors the design was changed by adding an external counterweight fitted onto the outside end of the crankshaft, this design carried through all the models to 1930. I'm sure some of these bolted on counterweights came loose and demolished the engine. These counterweights can be seen here.
Only 7 of these rare tractors exist today.