The piston ring compressor makes the job of installing the cylinder barrel over the piston and rings easy and trouble-free, preventing broken piston rings during reassembly.
The thin-walled band of the ring compressor is sized for use with 75-80mm pistons, as used on BSA A65, A70, B40, and B44 models, as well as the Triumph 750 and Norton 850 models. Universal fitment also allows for compatibility with some American and Metric applications.
The band is adjusted by tightening the screw that passes through the open trunnion and is threaded into the pivoting trunnion. When the band is fully tightened, it compresses the piston rings into their grooves on the piston, allowing the cylinder barrel to be positioned over the top of the piston. Gradual loosening of the band screw will allow the cylinder to drop down over the rings as the ring compressor slides down the piston until the cylinder bore is located over the set of piston rings.
A pair of ring compressors will be needed for use on twin-cylinder engines. It is recommended that the pistons are supported underneath by using blocks that span across the cylinder base to allow easy removal of the ring compressors once the cylinder has been fitted over the piston rings.