1. Technical Bulletin Bulletin No TCH 001 044 A Effective Date 2 1 98 Cancels NA Page 1 of 1 Subject UNLOADER PISTON CHANGE FOR THE TF 550 750 COMPRESSOR A design change has been incorporated into the unloader piston complete of the Tu Flo 550 and Tu Flo 750 air compressors To minimize compressor unloader leakage a back up ring was added to the unloader piston o ring groove The back up ring enhances the seal between the unloader piston and unloader bushing The new and old style unloader pistons are interchangeable without the need for additional modification to the cylinder head The new style unloader pistons are available in the following kits 107515 Unloader Kit 107516 Cylinder Head Maintenance Kit o ring back up ring unloader piston New Style Unloader Piston