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Discussion in 'Heads and Cylinders' started by Rudz, Jul 14, 2015.
Why are people slapping on Reed valves without proper cylinders? Won't it actually rob compression?
A reed valve will work just fine with a window port in the piston skirt...
It will work even better with a boost port.
Ahhhh I see
The window in the piston is the most important part, if there was no window in the piston (or cut-away from the piston skirt) then you are not increasing your intake timing duration, witch is -among other things- what converting to a reed valve would allow you too do.
Alternatively, if a "boost port" is cut from the bottom of the cylinder bore (underneath the intake port) up through the intake port, and out the top, to the same height as the transfer ports, the piston modification is not required, but will still provide an improvement in overall flow, and performance.
The "boost port" also known as -in our case- the third transfer port (cut from the intake port, up, to the height of the transfer ports) increases the performance gained by creating another path for this extra intake charge (if you do indeed increase the intake timing) to get into the cylinder.
Reed Valve conversion without Piston Window or Boost Port = Meh
Reed Valve conversion with Piston Window and no Boost Port = Improved low end power, possible loss in top end (depending on window size/shape)
Reed valve conversion with Piston Window and Boost Port = Even more improved low end power, with more top end power too.
If you have any other question don't hesitate to PM me.
Ok maybe i did not do my motor right then. I have a crappy dax gen IV with a gt5 cyl on it. The original cyl had tiny ports. I have the RSE reed, I widened both intake and exhaust ports, raised the exaust 1mm, lowered the intake 1mm, opened up the transfers, and skirted the bottom of the piston to match the intake port. Oh i also ramped the top of the piston to match the transfers......Do i also need a window on the piston after all this?
If running a reed valve, I would HIGHLY recommend the window in the piston.
Here is a pic of the window I make:
Here is the best pic I have of it actually done to a piston.
The top of the windows are "angled" on this one, on my new pistons I cut it like the drawing, flat on top:
Don't mind the notch on the left side of the left window (I messed up while machining it >.<)
Looks interesting. My bike goes fast but doesnt feel fast getting there. I dont have a side cutter to make that window unless i can find something to fit my dremel.
I did all that with a dremel tool.
The "carbide" burrs are what you want for aluminum.
I use the "e-z lock" cut off wheels to rough it out, then various shaped dremel 1/8" carbide burs to clean it up.
The Dremel really is an amazing tool
Well thanks for the info, it should be what this motor needs . Right now my workspace is filled with guitar amp stuff as building handwired amps is another hobby. But i will get to this soon.
Nice work, do you sell these pistons?
Prob a dumb question but is the 'boost port' the same as '3rd transfer port'?
What's the best way to go about cutting the boost port without risk of high spinning carbide bit slipping and scratching the inside of cylinder ?
For the rse reed valve setup which windowed piston is better. See the pics below. Here's the link as well.
I'd like to know the answer to this question as well
I cut the ports using a mill.