Note: This article was written in 1993, long before there was available software for this application. Race Logic built every APP in spreadsheet form from scratch. Our software has been updated annually and is proprietary to us. Today’s available software does not cover the tiny details that make the difference.

Article reprinted from SNOWWEST & WINNING EDGE magazines.

Inside every two-cycle engine are ports that regulate air flow. These ports, intake, exhaust and transfer, have specific jobs to do within the motor.

Interaction between these ports is very important. Proper modifications of these ports may be one of the biggest ways to get more horsepower. Done improperly, they can ruin the motor.

Small, precise changes can make a big difference. These ports actually control the way your motor breathes. Modifying these ports (openings) on the cylinder walls properly can vastly improve the efficiency of the motor, thus giving you more power.

The first thing you need to know is what changes are needed to improve the motor. The second is to make the changes properly. The SportPort template system from Race Logic is a precise, transferable replica of a properly modified port, complete with a perfect guide for you to follow. With this template, all arcs and lines are exact with no variances, and are accurate to within .002 inch.

Since the first time someone tried to get more power from a motor, it has been an "eyeball" judgment call with the arcs and angles of the ports. If 100 cylinders, with exactly the same modifications done to each one, all done by the same experienced porting technician were laid out, there would be variances from one cylinder to the next. All would be done well, but without absolute uniformity.

The world of porting has always been fighting the problem of precise port grinding and perfect specifications. Computers and templates have answered that challenge. The process of specification design and template manufacturing is an extensive and calculated step-by-step procedure.

First, as the motor is being disassembled, precise measurements are taken;, head chambers are cc'd, squish clearances and angles are recorded, combustion chambers are measured and radiused. Nothing is left unchecked. With the motor disassembled, work begins on the cylinders. All ports are measured from top to bottom (top opening, width and side angles, radiuses and arcs).

With this information, the computer then is utilized. Without the accuracy of computer-aided design systems and specifically designed software, the rest would not be conceivable. All the information is entered into the computer. Then it is broken down into its most basic level (port durations, compression ratios, time areas at designed engine speed as well as numerous other elements). With all this information, it becomes evident where this specific motor is lacking or excelling.

Knowing what this motor will be used for (trail, drag, oval, etc.), respective needs are then plugged in. For example, in a trail design, you want to maintain or even increase low end and midrange and still get peak horsepower increases. To do this, you want to keep a long power stroke (low exhaust port) and increase port area. If the exhaust port is too narrow, it can be widened to a safe limit, or it can just be reshaped for more flow. The latter being better, since it gives an increase in the blowdown area where it's needed most.

Having done this, transfer duration may be increased for improved low end and midrange. Gaps will continue to be filled throughout the motor while changes are entered into the computer. With the changes plugged in, the computer will rebuild the raw data back to a set of new engine specifications. Along with the new specs, there's a new set of machine code files that input directly into CNC (computer numerical control) machines, which then can cut heads, machine cylinders and most importantly, manufacture templates.

Modifications are then made in the shop. With the changes made, it's time to test and fine tune the motor on a dyno and in the field. Once the modifications have been verified and fine tuned, it's then time to put the kit together.

The SportPort kit comes with templates for your particular model. It also includes an application page containing hints and tips and a detailed instruction manual. Free technical assistance is also available.

After reading the entire manual, complete with step by step instructions and drawings, the user will be ready to do the modifications to the cylinder.

Until SportPort, modifications were usually done on the kitchen table by an enthusiast who hoped he was doing more good than harm. Usually the results were disastrous, or done by a professional at great expense. The magnetic reusable template is aligned with the straight edge at the end of the cylinder providing the perfect cutting guide.

With today's new technology, computers allow for absolute precision of the specifications essential in the design of the porting templates. With a perfect guide, the template provides the user with an exactness never before achieved, even by the professional porting technician.

Article reprinted from SNOWWEST & WINNING EDGE magazines.