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Use of the hydrostatic transmission (HST) in compact riding mowers has recently become more widespread due to the fact that an HST provides considerably better mowing performance than a conventional manual transmission. In addition, there are now several manufacturers that are capable of building compact and efficient HSTs. The standard power train of an HST-equipped compact riding mower consists of the engine, HST, and transaxle, laid out separately and interconnected by a V-belt. As a result, the power transmission system is highly complicated, making maintainability difficult. The recently developed model PA540A and PA420A unitized power units are compact power packages combining a vertical gasoline engine, HST, and transaxle in a single structure that can be mounted with as few as 3 bolts, allowing much greater freedom in mower design.

Recently, motocross racetrack configurations have been changing from speed-oriented layouts to rider's talented performance-oriented layouts. This has created a demand for engines that can provide both power at high speeds and torque at low speeds as well as having quick response at all speeds. The most efficient way to achieve all round power range in the 2-stroke-racing engine was to increase the area of exhaust port and to vary the exhaust chamber volume at the same rate as the increased engine revolution. The authors developed an automatic exhaust control valve device called “KIPS”. In this paper we will describe how KIPS was developed, its output characteristics, and operation. Figure I shows a 1992 model KX250 motocross racing bike equipped with the newest KIPS device (3-Way KIPS).

Today one of the most essential features for engine-powered work machines is that it must be “user friendly”. The recently developed FD590V vertical shaft liquid-cooled 4-stroke V-twin engine is not only a lightweight compact engine, but has improved versatility in many applications of work machines by integrating the entire cooling system with the engine package. The engine is also a high performance, high quality engine designed to provide an improved working environment and easy maintenance. The engine features new technology for a unique liquid-cooled V-twin with excellent operating characteristics. This paper will explain the overall specifications and features of the FD590V, while introducing various technical aspects applied and the results of studies made during the design and development stage.

Abnormal combustion, which is a cause for engine failure, is explicated to be high speed knocking by multi-cycle analysis of the cylinder pressure data of snowmobile two stroke cycle engines operated at high speed and wide open throttle condition. A mini-computer was used for the analysis of the cylinder pressure data. Calculation of the entire cycle was conducted until an engine actually failed and the relationship between the engine failure and the conditions surrounding the knocking was made clear. Using the rate of pressure change as a quantitative evaluation method for high speed knocking, a combustion chamber shape with less knocking occurrence possibility was selected.

This paper describes aspects of the Kawasaki two-stroke engines for snowmobiles. Generally speaking, in order to obtain good results in developing engines for snowmobiles, it is important not only to investigate the engines themselves, but also to match their performance with those of the snowmobile, including their power-transmitting system. Kawasaki has developed an ignition system for firing two plugs per cylinder, which prevents abnormal combustion and results in higher performance.