such as a Honda CRF 450, which had greater torque at both low(17% increase) and high (9% increase) engine speeds, and also produced more brake horsepower up to around 30% more at functional engine speeds. The engine was also considerably smaller and lighter, as the cylinder head assembly was not as large. A company in the UK called Roton Engine Developments made some progress in 2005 with a two-rotor (one for inlet and one for exhaust) single-cylinder Husaberg motorcycle engine. They filed patents and got an example running in 2006, but were backed by MG Rover which subsequently went bust, leaving Roton without enough funds to continue. The designs surfaced some years later in Australia with Engine Developments Australia Pty Ltd. A prototype casting was produced in 2013 on a Kawasaki Ninja 300 parallel twin unit. This unit is still in development phase at the time of writing but is significant as it has the potential to run much higher compression ratios than even other rotary valve engines due to a significant but undisclosed new cooling method of the combustion chamber and the ability to eliminate the throttle completely, making it vastly more economical at lower engine speeds, so it is claimed. A proven completely successful automotive rotary valve engine has been built by the late Ralph Ogden Watson of Auckland New Zealand, during 1989. The car has covered many trouble free miles from that date and remains in use. Success was achieved as a result of Watson's academic approach to the problem of sealing, his study of previous designs, and his particular combination of knowledge of materials, machining skills, experience with engines, perseverance and realistic expectations. No new or only recently available materials were involved. Full details of the development of the car and engine appear in the book "Ralph Watson Special Engineer," first published 2004, ISBN O-476-01371-2 and available free and easily searchable, on the internet as of 2020. The car is currently owned by Ray Ferner. Two-stroke engines A rotary valve in the form of a flat disc, also known as a disc valve is widely used in two-stroke motorcycle engines, where the arrangement helps to prevent reverse flow back into the intake port during the compression stroke. Austrian engine manufacturer Rotax used rotary intake valves in their now out-of-production Rotax 532 two-stroke engine design and continues to use rotary intake valves in the 532's successor, the