Good old times blog - A husky handful
In the beginning of the 1960s the Husqvarna factory chief engineer Ruben Helmin had an idea of putting two 2-stroke engines together. It would result in a potent twin power plant with a displacement of half a litre. It wasn't until in the autumn of 1967 that he began developing his thoughts into reality.
Helmin used two 250cc engines and integrated them into one power unit. The pistons were the same as the regular 250 with two rings on each piston as opposed to the later 504 version with only one ring for each piston. The result was a 492cc motor mounted into a 360 frame. The modifying consisted of other engine plates and used the gearbox and parts from the 420cc Grand Prix bike, then used in the world championship.
Read the full story of Husqvarna’s 490cc twin here