Welcome back to Airborne Productions. Today we're going to be looking at how to make a two-stroke expansion chamber the easiest possible way. There's quite a bit of information out there on how to make a proper expansion chamber, what it should look like, the math involved, etc. But today I'm going to show you a very simplified way that really anybody can use to make one. If you're familiar with two strokes, you're aware of what an expansion chamber can do. It can really open up quite a bit of power on your motorcycle. Like I stated earlier, there's a lot of information out there. You can spend hundreds of dollars on programs to figure out what you need. In order to simplify this, we're going to use one free Excel sheet that does all the math for you. All you need to know are three numbers really. You need to know your target peak RPMs, need to know the diameter of the exhaust port on your bike, which is what diameter you'll use for the beginning of your exhaust. You'll also need to know the duration that the exhaust port is open. You might be able to find the exhaust port duration for your motorcycle online somewhere, which means you can skip this step entirely. If not, I will show you the easiest way to measure it. Start by removing the exhaust in order to expose the exhaust port. Then remove the spark plug and shine a light into the cylinder through the spark plug hole. The next step is to find a way to measure the position of the crankshaft right when the exhaust port starts to open, as well as right when the exhaust port completely closes. I removed the left side cover to expose the stator assembly, which will rotate around a fixed point, bolted to the crank. Simply attach a pointer to the axis of the crank, in this case the zip die for me. And find the angle between the opening and closing positions of the exhaust port. With the light shining through the cylinder, observe the point where light just starts to shine, pass the piston into the exhaust port, and the point where light stops shining through the exhaust port entirely. This can be done with a simple protractor made out of paper or any other material, and by taking note of where the pointer aims on this protractor. Instead of this method, I recorded both of these positions on video, and simply measured the angle using an image editing software such as Photoshop or GIMP, but either method will work fine. My bike's exhaust port duration turns out to be approximately 174 degrees. Now that we have our numbers figured out, it's time to hop onto the spreadsheet. It's possible to do it on a smartphone, but I find it easier to use a computer. There are a plethora of programs available, some free and most costing money, but I find this particular spreadsheet to be the most simple, although you might be able to squeeze out a little bit more power with some more complex programming and math. This spreadsheet is completely free, and the link for it will be in the description. First, open it up in either Excel or in Google Sheets, which is free and what I am using. Next, input the three variables into the spreadsheet. If you know more about two strokes, you can adjust the other left side variables to your liking. I am going to use these recommended values for simplicity. With everything adjusted on the left side, use the values on the right side of the table, as well as the plot of the expansion chamber and the table of pipe diameters in order to find out what size the pipe and cone pieces need to be. If you have a slip roll and sheet metal, you can fabricate your own cones. However, I will be purchasing my cones online, as I do not have access to a slip roll. Find pieces that match the dimensions required and you are set. As for thickness, this will need to be considered when inputting values into the table. I will be using 20 gauge, which is about 40,000 of an inch. Thicker material will be easier to weld and can be used, but it is not necessary. Your expansion chamber can be made out of any exhaust material, such as mild steel, stainless, or even titanium for weight reduction. I am going to use mild steel to save money to make welding easier. Any welding process can be used to combine the pieces, as long as proper heat control is applied, in order to not blow through the material. I will be too welding, as this is what I have the most practice with. The final step in the early stage is to practice welding pipe. I personally don't have much experience welding pipes and tubing, nor have I practiced welding steel this thin that much. However, there isn't a huge skill gap between simple butt joint welds and tubing welds. Add a quick practice and technique will make this a breeze. This wraps up part 1 on how to make your own expansion chamber. The next video will look at mocking up our pieces, as well as fabricating.