On January 20, 2015, at 1220 mountain standard time, a Piper PA-28-140, N4666R, experienced a loss of engine power during takeoff from the Helena Regional Airport (HLN), Helena, Montana, and subsequently impacted a shed and a house. The flight was operated under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. The private pilot was not injured; the passenger/owner sustained minor injuries. The airplane sustained substantial damage throughout its structure. Visual meteorological conditions prevailed for the personal flight that was destined for Missoula, Montana. No flight plan had been filed. The pilot reported that he performed a thorough preflight inspection, which included checking the flight controls, and fuel and fuel sumps; no discrepancies were noted. After the engine started, and while it was warming up, he contacted ground control for a clearance to taxi to the active runway for departure. The ground controller cleared him to taxi the airplane to runway 27, where he commenced with an engine run-up. During the takeoff roll, the airplane rotated at 65 mph. During the climb out, he stated that it was quiet; the engine was not developing full power. The pilot stated that there was no safe place to land straight ahead, and as the engine was still running, he decided to turn back for the airport. The pilot stated that they were about 350-400 feet above the ground, and the engine was developing 2,300 rpm when he made a shallow left turn to return to the airport. The airplane could not maintain altitude or airspeed, and it collided with a house. The owner/passenger reported that he purchased the airplane about 2 weeks prior to the accident. An annual inspection had taken place in August 2014. On January 16, 2015, the owner called Executive Aviation, a fixed based operator (FBO), and requested that the airplane be topped off with aviation fuel; the airplane was refueled with 26.3 gallons of fuel with the majority of the fuel placed in the right fuel tank. The owner stated that the airplane had been tied down outside on the tarmac since August and had accrued about 2.19 hours since the annual inspection. An officer from the Helena Police Department reported that the airplane struck power lines, a tree, a propane tank, and came to rest in a shed and adjacent house. The responding Federal Aviation Administration (FAA) inspector reported that both of the airplane's wings had separated from the airframe. Both wings' fuel tanks were breached in the accident sequence, blue colored liquid was near the right wing pooled in the snow. An engine inspection was performed on April 28, 2015, at Helena Aircraft, under the supervision of an FAA inspector. A visual inspection of the engine revealed no obvious damage to the engine. The engine remained attached to the engine mount, and the airframe. The fuel strainer screen, electric fuel pump screen, and the air filter contained no obstructions. The top spark plugs were removed, and manual rotation of the engine produced thumb compression in all cylinders in firing order. The magneto switches were turned on, and the spark plug leads produced spark at each cylinder when the engine was manually rotated; magneto-to-engine timing was also established and within manufacturer specification limits. The spark plugs were placed on a spark plug test bench, the top No. four, and bottom No. two did not fire. The carburetor functionally checked, and appeared to function normally when the throttle and mixture were manipulated. The carburetor was removed with partial soot identified in the throat area. The accelerator pump functioned properly; however, the retaining cotter pin was not present. The carburetor bowl was empty. The fuel selector was selected to the right fuel tank inside the cockpit. The right main fuel tank filler port was placarded to allow auto gas; there was no fuel inside the fuel tank. A detailed report is attached to the factual docket for this accident.