“You Can Never Get Too Bored” crank shoving those new forged pistons up in the valves, or maybe not even making their way up the cylinder. The engines bore size is the diameter measurement of its cylinders. The stroke is the distance the piston travels from top dead center to bottom dead center (and vice versa).These values are both measured by inches or millimeters. The displacement then equals the volume in all of the cylinders that’s swept by the pistons as they move. -- Otherwise the volume displaced by the piston from the bottom to the top of the stroke. Remember about torque a bit ago? That is why you want to change up the engines stroke value. Larger stroke increases the crankshaft’s leverage. Then BAM!! – MORE TORQUE. Throw the confetti and cut the cake. The speed celebration begins. Don’t forget the smaller stroke crankshafts though. They get better RPM’s and easier on the connecting rods. Depending on the rod lengths depends on what you feel is best for your overall initiative. I’m going to say it again and again; don’t go jacking your stuff up; MEASURE RIGHT. And here’s how you do it! I can’t just throw a formula at you and wish you luck with no numbers to plug in. That would be pretty damn rotten of me. Let’s start with measuring the stroke length to figure how far this piston travels when it’s cranked. This isn’t difficult. I’m a chick. If I can do it, surely you can manage. First you’re going to need what’s called a DIAL INDICATOR GUAGE for measuring the cylinder values. This tool is calibrated in .001 inch (.0025 centimeters) or .0001 inch (.00025 centimeter) as the units for the most accurate reading. Ok. Remove the cylinder head. Then position the piston so it’s pushed all the way down at bottom of the cylinder. (Just leave it like this for measuring the bore anyways). Next, mount the bridge on the top of cylinder. Insert the dial indicator into the hole enough to touch the piston, and tighten the locking screw of the measuring dial. Now you want the face of the dial indicator so the needle points at zero. You are going to turn the crankshaft with an Allen wrench. Keep an eye on the dial so you can count how many times the needle fully revolves by how many hundredths (or thousandths depending how you’re measuring) till it reaches top dead center. Write that down. Put it aside for a second. The bore measurement is similar. The measuring sled consists of three different guides and actuating plunger that adheres on to get a precise reading. So you take an outside micrometer set and measure across the gauge until zero aligns with the needle. Then insert the gauge into the bore, and kind of rock it back and forth till inserted evenly in the pipe. Your lowest reading is when the gauge is square on the bore and the needle reverses directions. Depending on if more or less than zero will be your indicator of an oversized or undersized bore. Go back and look how that number reads. Follow this chart for the bore. This way even if you plan on having it machined, you have a starting point.
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