What are the function of reed valves on a motorcycle?
there are quite a few types,reeds/reed valve/disc valve..all 2 strokes have some sort of reed system...idea is that fuel is sucked past the reeds,these then close letting the fuel travel where it needs to go,opening when its time to suck fuel in....and so on
GuardrailJim and Badobses---, you both got it almost right. You other guys, take a lesson. First, Jim Bad should have said fuel is pulled into the crankcase, through the reed valves. The crankcase is a small sealed off area on a two stroke, just larger than the flywheels. Old days, the piston skirt was used for a valve, opened when the piston was on the way up, closed on the way down. Both systems use the piston skirt to open and close the exhaust port, which opens when the piston is on the way down on the power stroke, normally about half way, give or take a bit. Intake, into the combustion chamber starts when the transfer ports open, which is a bit after the exhaust port opens, and closes just a bit after the exhaust closes. With the reed valve, mixture is pulled into the crankcase at any time the case pressure goes below atmospheric. Also stops, by the reed valve, as soon as pressure goes over atmospheric. This lets the engine induce a fair amount more mixture than was possible with a piston port, and no blow back of mixture through the carb. This is a simplification of a very complicated piece of air flow. One will know chap I know, who also built some of the best, if not the best 2 stroke exhaust went back to college, got a Doctrate on accoustics before starting design of his expansion chamber systems, and THEY WORKED! Sorry, I did not mention disk valve engines the first time, in effect kin to the piston port, except they are timed for opening and closing to be at proper time to get maximum flow into the crankcase. Less blow back than with a piston port. Between piston port and reed in power, all else equal. Reed valves are all-round best. Cheers, Tomcotexas.
They allow a fuel/air mixture to enter the area under the piston in a two stroke engine on the compression stroke, as it is a one way valve when the piston is coming back down the gases are forced up through the tranfer ports into the combustion chamber.
