Research And Development Of Valve-train For LC250 Motorcycle Engine

To solve the loss of contact between cam and follower of the LC250 motorcycle engine valve train in the market,and in order to ensure the engine performance and the high speed reliability of Engine Valve train,based on the theory of kinematics and dynamics analysis, this paper studies and designs the Valve train of LC250 engine . It describes design, CAE analysis, optimization and comprehensive test of valve train in this small high speed motorcycle engine.In this paper, at first, it used AVL TYCON software to set up simulation model of the engine valve train, introduced the establishment and evaluation standards in detail, described the design of cam profile and factors that influence the profile, and analyzed the motion characteristics of valve, cam follower and the reason of loss of contact between cam and follower. Then,the new cam profile was designed and analyzed according to above research. Results show that the new cam profile could reach the design target and solve the problem of loss of contact between cam and follower, and the performance of the engine is the same as before. After that, a new sample cam according to the new design was developed, and the performance comparing test was conducted between the new sample cam and the old one in the same engine conditions. Testing results show that the power of the tested engine was increased by 5.41%, torque was increased by 1.42% and fuel consumption was reduced by 5.5%. Finally, engine performance and endurance test on the bench and noise test results could reach the requirements of motorcycle industry standards. Loncin started the mass production of this engine in October, 2009. Up to now, products quality is stable to satisfying customers. All these proved that the new design of cam was feasible.Based on the reality of our company, according to the characteristics of the small high speed engine, over speed and change speed test method have been issued firstly for the engine valve train performance testing in motorcycle industry in China. It solved the problems including that simple testing method, not enough equipment and simple evaluation, etc. It is the simplest, the most reliable and the most effective method to evaluate valve train comprehensively now.Additionally, a platform for further valve train optimization and design of LC250 engine and new engines in our company has been set up effectively. Modified LC250 engines have occupied one part of the motorcycle engine markets with good benefits and honors for Loncin Company.