Editing Two-stroke engine (section)

==Power-valve systems==
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{{Main article|Two-stroke power valve system}}
Many modern two-stroke engines employ a [[Two-stroke power valve system|power-valve system]]. The valves are normally in or around the exhaust ports. They work in one of two ways; either they alter the exhaust port by closing off the top part of the port, which alters port timing, such as [[Rotax]] R.A.V.E, [[Yamaha Corporation|Yamaha]] YPVS, [[Honda]] RC-Valve, [[Kawasaki Heavy Industries Motorcycle & Engine|Kawasaki]] K.I.P.S., [[Cagiva]] C.T.S., or [[Suzuki]] AETC systems, or by altering the volume of the exhaust, which changes the resonant frequency of the [[expansion chamber]], such as the [[Suzuki]] SAEC and [[Honda]] V-TACS system. The result is an engine with better low-speed power without sacrificing high-speed power. However, as power valves are in the hot gas flow, they need regular maintenance to perform well.