ChrisCarsonMarine
08-30-2025, 01:09 PM
Seeing as how reeds are now a popular subject of interest I thought I might share some thoughts.My 1st thought is it's amazing they put up with what we put em through.
They open and close on each rotation of the motor...oops,they open and close only on the up-stroke...so,cyclicly they move at twice the engine RPM.
At 6000 rpm the motor turns over 100 times a second,the reeds do the same but remember they rest closed one half of the time,so they are cyclicly opening and closing 200 times a second.At 7500 it's250 tps,at 10000 it's332 times per second.
An engine has to be balanced in all aspects,intake potential,exhaust,and porting,and the factory pretty much knew what they were doing,which is why we are often disapointed with the results achieved by our modifications.Fuel\air has to get in,be processed(burned effectively) and get out and a big change in only one sector is likely to not help much.
As to reed valve function,there are many variables.The reed needs to open enough to feed the need,but close fast enough to stop re-flux.As engine speed increases the "matter in motion"princibles come more and more into play,the"heavier"reed not being to change direction fast enough to close timely.In my opinion this is where the larger reed cage comes into it's own,allowing more airflow without the petals having to open as far,resulting in faster closure.Less petal movement,and stiffer material allow for higher rpm's without the petals slamming shut by crankcase pressure,shortening life drasticly.
So,in order to not reed valve govern a motor we need a proper combination of window area,and reed tension suited to the air and rpm requirements of the motor,this is why we offer different materials,tensions etc.
Regarding reed stops,I think of them more like safety belts in cars,They allow normal movement but keep from blowing the reed off in a backfire.Does anyone realize that removing the stops looses more crankcase compression and vavuum than milling 060 off the front half gains?
If the motor came with stops I reccomend using them,and for a 7000 rpm and below I perfer the smaller cages,Chris
They open and close on each rotation of the motor...oops,they open and close only on the up-stroke...so,cyclicly they move at twice the engine RPM.
At 6000 rpm the motor turns over 100 times a second,the reeds do the same but remember they rest closed one half of the time,so they are cyclicly opening and closing 200 times a second.At 7500 it's250 tps,at 10000 it's332 times per second.
An engine has to be balanced in all aspects,intake potential,exhaust,and porting,and the factory pretty much knew what they were doing,which is why we are often disapointed with the results achieved by our modifications.Fuel\air has to get in,be processed(burned effectively) and get out and a big change in only one sector is likely to not help much.
As to reed valve function,there are many variables.The reed needs to open enough to feed the need,but close fast enough to stop re-flux.As engine speed increases the "matter in motion"princibles come more and more into play,the"heavier"reed not being to change direction fast enough to close timely.In my opinion this is where the larger reed cage comes into it's own,allowing more airflow without the petals having to open as far,resulting in faster closure.Less petal movement,and stiffer material allow for higher rpm's without the petals slamming shut by crankcase pressure,shortening life drasticly.
So,in order to not reed valve govern a motor we need a proper combination of window area,and reed tension suited to the air and rpm requirements of the motor,this is why we offer different materials,tensions etc.
Regarding reed stops,I think of them more like safety belts in cars,They allow normal movement but keep from blowing the reed off in a backfire.Does anyone realize that removing the stops looses more crankcase compression and vavuum than milling 060 off the front half gains?
If the motor came with stops I reccomend using them,and for a 7000 rpm and below I perfer the smaller cages,Chris