1. If the engine has been completely disassembled so that the cylinder block is open, thoroughly clean it inside and out. If not already done, remove the 5 bolts securing the oil line cover to the side of the cylinder block, remove the bolts and cover, and discard the old gasket. Also remove the old O-ring located on the centering collar on the clutch side.
2. The easiest way to clean the engine block is to soak it in a bath of cleaning solution, allow the solution to soak in, and then clean the block with wire brushes, scrapers, and probes. Be careful not to scratch the contact surfaces. Usually sediment builds up around the pockets of the cases and needs to be removed.
3. Rinse the unit well with water from a hose and, if possible, blow with compressed air, then dry and wipe dry with lint-free cloths.
4. Lubrication channels should be cleaned with a small brush. If possible, blow them out with compressed air and squirt clean engine oil inside to make sure the passages are not clogged.