S&S Super Stock Cylinder Head Kit Installation Instructions for 1984 And Later Evolution Big Twin and Sportster Engines


Filed Under (Harley Davidson) by admin on 28-11-2010

check Piston Alignment in Cylinder Bore The purpose of this procedure is to check for and correct possible piston misalignment in the cylinder bore. During normal manufacturing, engine components such as crankcases, cylinders, and connecting rods can be machined to dimensions within factory specifications but on the extreme ends of the tolerance range. Sometimes these components when combined together form an assembly that is borderline or actually “out of print”. The worst result is that the pistons can run cocked in the cylinder bores causing the connecting rods to thrust to the sides exerting unnecessary stress on the pistons, rings, rod bearings and other related parts. This procedure is not the same as “blue printing”, but it provides almost the same result. We feel that not enough emphasis is given to checking the piston alignment in the cylinder bore. NOTE – All engines should be checked upon disassembly. This applies to any engine receiving new pistons which includes those being completely overhauled. CAUTION – Pistons which do not run true in cylinder bores may cause excessive connecting rod side thrusting. This may lead to premature ring, piston, connecting rod and rod bearing wear and eventual failure of these parts. Visual Procedure A. Reinstall cylinders on old pistons without rings. Hold cylinders securely in place. B. Move piston tight toward camside of engine. C. Turn engine over in normal direction of travel 2 or 3 revolutions and observe piston during process. D. Move piston toward driveside of engine and repeat Step C. If misalignment exists, piston will appear closer to cylinder wall at one point around circumference. Condition can be corrected by bending rod in opposite direction. Figure 1 shows an exaggerated side view. E. Repeat Steps B to D for other cylinder. F. Remove pistons and cylinders. Observe pistons for wear spots on sides above top compression ring. If either side near wristpin is worn clean while side opposite is carboned up, then piston was not running straight and true in cylinder bore. Piston will also generally show diagonal wear pattern on thrust faces of skirts and possibly signs of connecting rod to wristpin boss contact inside piston.