on 7 november 1960 the first new 650 cc norton manxman was launched for the american market only. by september 1961 the norton 650ss appeared for the uk market, the 750 cc (atlas). by 20 april 1962 for the american market as they demanded more power, but the increases to the vertical twin engine's capacity caused a vibration problem at 5500 rpm. a 500 cc vertical twin is smoother than a single-cylinder, but if the vertical twin's capacity is enlarged vibration increases. the 750 norton atlas proved too expensive and costs could not be reduced. financial problems gathered.