Starting Port Molds

Starting to make some molds of the ports on the stock cylinder, so that I can take measurements.

Seal off the inside of the cylinder. This is a stock 1978 NC50 cylinder.

I am going to have to do this in two steps, since I have to set the cylinder at an angle to fill the exhaust port. The transfer ports I can lay the cylinder flat. Grease the inside of the port:

Microwave the molding compound. In this case, I am using Composimold:

Pour into the exhaust port:

Fill it up:

On the left is the Composimold exhaust port from the stock NC50 cylinder. I get Composimold from Amazon, http://smile.amazon.com/ComposiMold-FC40-Reusable-Material-40-Ounce/dp/B0096BSQ2S/ref=sr_1_1?ie=UTF8&qid=1438548890&sr=8-1&keywords=composimold. I used to use another molding material, that was a reusable molding compound available in different stiffnesses. It was like a silicon rubber, but turned to liquid in the microwave and reverted back to rubber state quickly. An example of this is the ZXI 1100 cylinder head mold on the right. I still have some, but I am using it sparingly since every time you use it, you introduce some contamination. I don't like the Composimold that much, but it is readily available.

Now the transfer ports.

From the port mapping, I get a rear transfer port width of 18.54 mm as a cylinder segment width. Converting to chord length, this is 17.88 mm. Measurement of the mold, I get 18.02 mm.

From the port mapping, I get the magneto side transfer port width of 19.20 mm as a cylinder segment width. Converting to chord length, this is 18.47 mm. Measurement of the mold, I get 16.51 mm.

From the port mapping, I get the clutch side transfer port width of 19.24 mm as a cylinder segment width. Converting to chord length, this is 18.50 mm. Measurement of the mold, I get 16.67 mm.

From the port mapping, I get an exhaust port width of 29.42 mm as a cylinder segment width. Converting to chord length, this is 26.83 mm. Measurement of the mold, I get 22.02 mm.