SBT's sleeves are an economical solution for repairing cylinder blocks back to OEM specifications. SBT's jet ski sleeves are made of a proprietary cast iron alloy and are centrifically-cast. They are identical to the sleeves used in SBT's remanufacturing process.
The purpose of a jet ski cylinder sleeve is to provide a wear surface for the piston rings. As the piston moves in the cylinder, the cylinder walls can become very worn and damaged. In such cases, the use of a sleeve made of hard metal can restore proper clearances to an engine.
There are two types of sleeves: centrifugal spun cast iron and poured cast iron. Poured cast iron is simply poured into a cylinder casting mold. This type of jet ski sleeve is usually more prone to weakness and porosity. The spinning method used to create centrifugal spun cast iron draws out impurities and air pockets from the raw casting material's center to the outer surface, which is then removed. The end product is a sleeve material that is greater in micro-structure and density. The jet ski sleeve will then withstand greater loads without losing cylindrical roundness or shape.
Another advantage of SBT's cast iron sleeves is that they wear longer and are more resistant to overheating than aluminum liners.