?'s regarding reed valves, boost porting and piston porting.

B

bigbutterbean

Active Member
I have heard some discussion regarding boost porting and reed valves and have a basic understanding of it. I have also heard discussion regarding piston porting, or drilling a hole in the side of the piston that faces the intake port. what does drilling a hole in the piston good for, and what does it do? Do I need reed valves to drill a hole in my piston?
 
Hi, yes u do need reeds 2 port the piston. Stock, ur piston acts as a valve between the intake port & crankcase, & the motor intakes 2 the crankcase thru 60 degrees. With reeds & a ported piston, the motor intakes 2 the crankcase thru 180 degrees & the reeds r the valve. I gave details of porting mods I used with reeds in the "reed kit" thread in the Hi Performance Tips section, that yielded roughly a 30% torque increase. Cheers
 
Sorry, ran outta phone screen. The reason 4 porting the piston is so the motor can intake thru it 2 achieve 180 degrees of intake (upstroke). On the downstroke mixture again travels thru it back into the port where the reeds stop it from exiting & it is forced thru the boost port & into the combustion chamber. The lower velocity of 180 degree intake nescessitates a large carb upjet. Cheers
 
so, you can either drill a hole in your piston or cut a boost port into your cylinder, but either one will increase your degrees of port timing?
 
No, porting the piston in conjuction with reeds is done 2 increase intake duration. A boost port, or ports, r additional transfer ports, transfering mixture from the crankcase to the combustion chamber. They r surface cut into the cylinder wall to the height of the transfers, from the intake port upward with reeds or between the intake port & transfers with or without reeds. cheers
 
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