Penton approached the KTM company, who at the time built bicycles and mopeds, to build a light-weight off-road motorcycle. The first Penton motorcycles were modified small bore motorcycles with a Sachs engine with improved suspension and details. The early motorcycles made their mark in International Six Days Trials (now called the International Six Days Enduro) competitions, Enduro races (Jack Pine in Michigan), Scrambles and Motocross with riders such as future Motorcycle Hall of Fame members Billy Uhl and Carl Cranke. The most popular size was the 125cc (Six Day), but they were also made in 100cc (Berkshire) and later, in 175cc (Jackpiner, in 1972), 250cc (Hare Scrambler, in 1973), and 400cc (Mint, in 1974). Beginning in 1972 fiberglass gas tanks were introduced and all of the 175cc and larger models utilized KTM engines. In 1974 longer travel gas forks, laid down shocks for longer suspension travel, lightweight plastic fenders and frames of high grade chrome-moly steel were introduced. In 1976 two distinct models appeared for the first time differentiating between Motocross use (MC5) and Enduro (Cross County). The MC5 MX series used longer travel leading axle magnesium slider forks to complement the high lever ratio rear suspension configuration making all but the 125 a competitive Motocross model.
Other, less-common models included the Mudlark observed trials motorcycle (made by Wassell in England), the Cafe MX (a dual purpose version of the Mudlark), the Hiro 125 (the Six Day with an Italian motor), the Woodsman (an enduro version of the Mudlark) and the K-R (Kenny Roberts)shorttrack racer.
Production, development and distribution was taken over completely by KTM Austria in 1978.