Millennium Technologies offers the widest selection of name brand pistons, gaskets, and rings like WISECO, WOSSNER, VERTEX, and PRO-X at a 20% discount.
We do not warranty cylinders where the clearance spec was requested by the owner. Millennium honors warranties for cylinders where we set the clearance spec. For example, grass-drag snowmobiles and youth mini-cycle racers need more piston to cylinder wall clearance because there is a short time between cold and full-throttle. Our technicians can advise you on the proper clearance spec for all sorts of fuel types, tuning, and usage patterns. The clearance between the piston to cylinder wall was too small considering the piston manufacturer’s recommended specifications. This piston has multiple seizure streaks equidistant around the periphery of the piston face. The melted blow-out spot usually occurs on the exhaust side and up to the center where the heat and pressure is the greatest. The piston crown got so hot that it melted.
The piston on the left suffered from too-lean carb jetting, too hot of a spark plug heat range or too low of an octane fuel for the engine’s compression ratio. The transmission-side crankshaft seal may be worn, allowing transmission oil to enter the crankcase and be burned in the combustion chamber, producing smoke at the tail-pipe, spooge at the header, and excess carbon on the piston crown.
This means that the jetting is rich, and perhaps the pre-mix ratio or oil type is too rich as well. The piston on the right is dark stained with no carbon spot under the crown. Looking under the piston crown a dark carbon spot should be visible taking up approximately 25% of the area of the underside of the piston crown center. The piston in the center is a great example of a perfect carbon pattern the color looks like hot-chocolate and the flow pattern resembles a leaf pattern. These three pistons have piston-crown burn patterns linked to carb jetting and fuel choice.