Aloha, thanks for the responses. Lets keep it going!! Many of us are on the same wavelength or thought pattern....
"Well it depends on your school of thought are you a believer that there is a constant flow down there or a flow in steps?"
Well there is a constant flow as someone mentioned at 13000 rpm things are moving fast, but I think the areas need to be addressed in steps, from air filter to expansion chamber.......to see what the weak or constrictions-turbulent areas are.
"My view is that the mixture is drawn in and will be stored in and around the crankcase and also in the cylinder transfers and will continue to be drawn in until the piston reaches TDC"
Yes my view too, but now with full circle crank there is less bottom crankcase volume and more direct from reeds-then under piston-then up the transfers flow. But with full circle crank there may be less "vortex" around the crank.
And also with full circle crank there is less crankcase volume, too but most important is the volume sucked in being displaced by the underside of the piston.
"Then there is a small time when there is no flow and then the piston begins to move downwards"
I understand that if you use too large of a carb, you will decrease the mixture velocity too much and loose the effect that you have with the velocity still pulling in mixture after the piston starts to come down.
"now some of the mixture will be thrown back out the reeds but the majority that was resting in and around the cylinder transfers will then just be pushed into the cylinder and the crankcase will be evacuated of most of the gas."
So now we need to close the reeds fast so there is minimal loss back through carb and max pressure up the transfers. The flow has to turn 360 degress from under the piston to up the transfers.
"So i really don't think that you need some special shape inside the crankcase just once there is no restriction to the incoming gas from the reeds.
The gas isn't flowing directly from the reeds to the cylinder it waits there for one stroke, just make sure you make the space quite large between where the cylinder skirt sits down and the crankcase. This is important when the piston is pushing the gas in the crankcase into cylinder transfers"
But how about the V shape of cylinder skirts here that the French tuners use? I feel, like many before have said, it is very important NOT to have any restrictions or sharp bends, but DO NOT polish as you need to create a boundary layer between the metal and the gases to make the flow faster. (but not like a golf ball). Also try minimize the turbulent areas.
Thoughts?
Frank
