What are locating pins?
Your Wiseco Two-Stroke piston has many unique features, one of the most critical are the locating pin. This important item located in the piston ring groove is there to keep the ring from rotating, which is all important in a two-stroke engine, where the scavenging ports are spread around the cylinder wall. You will not find these locating pins on your four-stroke or automotive piston, as these piston rings are intended to rotate freely around the un-interrupted cylinder bore.
If the piston ring were able to rotate around the piston, the ends (tips) of the ring would potentially snag in one of the scavenging ports, and catastrophic damage would be the result. When you assemble your two-stroke top end, it is very important that the opening of the piston ring tips be placed over the locating pin. In most cases, a piston and ring assembly will not fit into the cylinder bore unless the piston ring tips are located over the pin. We have seen pistons and rings that have been forced into place, which will damage the piston and ring beyond use. In the picture shown, you can see the loose assembly how it would appear before installing into a cylinder bore. Mechanics will collapse the rings with their fingers as the lower the cylinder over the piston, allowing the assembly so slide up into the cylinder bore. As always, please read your service manual, and also your Wiseco instruction form. After assembly and break in, get out and roost!
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