gkr
Street Racer
Posts: 9 
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Post by gkr on Jun 10, 2010 19:40:45 GMT 9.5
could someone explain REED and Rotary
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Post by tom on Jun 10, 2010 20:24:39 GMT 9.5
Reed and Rotary are different methods of controlling induction to the 2 stroke engine.
With a reed engine, there is a reed block in the crankcase that acts as a one way valve, so when the piston goes up, fuel/air enters the crankcase, when the piston goes down, fuel/air is pushed through the transfers. (the reed block is designed so that the reeds only open one way)
With a rotary engine, there is a disc valve connected to the crankshaft, and it has a "window" cut out of it that is timed to open for a portion of the crankshaft revolution. Normally you can spot the rotary as the carby is on the side of the motor (exception being the Italsistem "saetta" with a belt driven rotary valve located on the front of the crankcase.)
As far as i know, there are no longer production rotary engines being made. As far as CiK homologations go, the 100cc open engines have less power now than they had in 1999. Access to full-spec formula super A engines (optimised for 29mm slide carbies) has always been difficult in Australia. Not too many people found the sweet spot for the cut of the valve, the port timing, and the ignition timing required to make them sing. Those that did finished consistently at the front.
I'm not sure on the exact dates, but 100cc open motors were phased out completely a few years ago in favor of 125 "KF" TaG motors, (kind of like a beefed up leopard or rotax).
In my opinion, the 100cc open class is living on borrowed time. It is good now as obsolete 100cc open motors can be sourced very cheaply. (the last FSA motor i bought was $5,500, now you can get a 2nd hand one for $500!)
When the supply runs out, the class is over and we will have to move to 125cc Open.
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Post by lyonsy on Jul 9, 2010 2:29:49 GMT 9.5
from what i have seen the reed engine's are used because they are so flexible and have a power band with a large range they basicly go hard from idle to 20'000rpm
rotary's go hard and make more hp but they generaly have agressive valve cuts and the its all top end power but a standerd rotary is not a match for reed.
if you can get a rotary making a very broad curve of power but still with more power then a reed then u have an engine to beat.
if its all top end a reed will smoke ya every time
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