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Porting for Performance 2-Strokes

Custom Porting & Engine Mods for You
Cylinder Porting
Crankcase Porting
Big Bore
Head Design
Tuned Pipe Design
Your Choice!

Trail / Rec Riding
Race / Closed Course
Drag Race
Speed Runs
High Altitude / Hillclimb

Your engine looks the same on the outside!
Big difference on the inside!


How a 2-Stroke Works

Your 2-stroke motor is an air pump. It moves the air in pulses or charges. The spark plug fires and ½ of the stroke generates power. The exhaust port opens and combustion gas starts down the pipe at supersonic speeds. The cylinder pressure drops, and the fresh charge transfers thru the transfer ports, over the top of the piston, and out the pipe a little. Now, when the pipe is working, the wave hits the end of the pipe and reflects back with enough force to push the unburned charge back into the cylinder before the piston closes the exhaust port. This is the supercharge effect generated by a good pipe. Compression occurs and the sparkplug fires before TDC to create maximum pressure after TDC. At 8000 rpm your engine fires 133 times per second! Not much time to move the air required for top performance.

The basics are: More Air = More Torque. More air at a lower rpm = more torque available.

  

How Does Porting Help You??



Ported BB 1300 Cylinder in Ported Crankcase w/ Reed Spacer
Casting marks, machined edges, and Nicasil protrusions in the port chamfer area, all slow or disrupt the airflow. Cylinders need to match the crankcase, and the airflow from the reeds must reach the base of the transfer ports without restriction. Careful work to smooth and match the surfaces will improve the airflow. Crankcase porting improves performance from idle up to full throttle. Most noticeable is the bottom end torque, and faster acceleration.

Great improvement with Crankcase Porting:

Ski-Doo (Rotax) 670 & 583.
Arctic Cat: 700 & 1000 T-Cat.
Yamaha: 700 SX-R, Mtn. Max.
Polaris: 700, 800 - Good improvement.
Yamaha 12-1300 GPR - Good improvement

“The Power to Win, is a lot of little things, done right.”
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