Get your pistons lightened, balanced and angle cut while they are here getting repinned. Now only $200
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your rods too. From $200 to $225
Parker Enduro 2000 John Lane #48 John Marles #3
Why Welded Top Pin Pistons
Since the invention of the two stroke it has been plagued with the problem of the ring locator pins loosening up with time and eventually falling out of the piston. Why is this a problem? Well, when the pin falls out of the piston it get wedged between the piston and the cylinder causing the motor to seize. The purpose of the ring locator pin is to hold the ring in one location so it won’t rotate around the piston and end up with the ring gap in a transfer port or worse yet the exhaust port. If the ring finds itself in this position it expands outward and the piston breaks it off when it passes the top of the port.
This loose pin has been rubbing on the cylinder wall
Another problem with the locator pin seems to be the inability of the manufacturer to drill the hole it's pressed into to the proper depth. When the whole is drilled too deep the pin can work its way inwards leaving nothing to stop the ring from moving around the piston. The final problem with the ring locating pins is the material used to make the pin. Most pins are very soft steel. The pin should be equally hard or harder than the ring since the ring is the changeable part. In other words the ring can eventually wear out the pin.
Here is a factory top pin piston where the ring has worn clean through the soft locator pin.
Most pistons with loose locator pins have 100s of hours of run time left on them but are rendered useless because of the loose pins. Some people say, Just buy new ones. Well, despite the unbelievably high price of new pistons they still come with the same inferior pins just waiting to fall out. Nothing is indestructible but this is by far the best method to date of pinning a piston.
Welded top pin pistons address all these problems and present the perfect solution.