On returning from a flight in the local area, the aircraft was cleared for a straight-in approach. When the gear was selected down the in-transit light illuminated and stayed on. The gear warning horn sounded and a go-around was made from short final. Following a flypast, the Control Tower confirmed that the wheels were only partially extended. As the aircraft was climbing through about 700 feet, there was a surge of engine power and the aircraft yawed from side to side, mainly to the right. The pilot assumed that the right engine had failed, closed both throttles and made a gear-up landing on the grass alongside the runway. Initial investigation revealed that the gear motor circuit breaker had popped. This was a known fault with the aircraft, although the pilot had not been alerted to it. Although fuel was found in the right main and both auxiliary tanks, none remained in the left main and the left engine system was devoid of fuel. During his pre-flight inspection, the pilot had evidently over-estimated the quantity of fuel in the left main tank. He had limited experience on multi-engine aircraft and had not been formally checked on asymmetric handling procedures for some 4 years. Under the circumstances, he elected not to attempt to maintain height on one engine and concentrated on achieving a safe forced landing.