Yamaha 55DEHD Service Manual

Also see for 55DEHD: Rigging guide Rigging guide

Checking the piston diameter1. Measure the piston outside diameter atthe specified measuring point. Replacethe piston if out of specification.Checking the piston ring side clear-ance1. Measure the piston ring side clearance.Replace the piston and piston rings as aset if out of specification.Checking the piston pin boss bore1. Measure the piston pin boss bore.Replace the piston if out of specification.Checking the piston ring1. Measure the piston ring dimensions.Replace the piston ring if out of specifica-tion.2. Level the piston rings 1 in a cylinder witha piston crown.3. Measure the piston ring end gap a at thespecified measuring point. Replace thepiston ring set if out of specification.POWR5-27 6885J11Power unita69R50310Piston ring side clearance:Top piston ring a:0.05–0.08 mm(0.0020–0.0032 in)2nd piston ring b:0.03–0.06 mm(0.0012–0.0024 in)ab68850450Piston outside diameter:81.935–81.955 mm(3.2258–3.2266 in)Measuring point a:20.0 mm (0.79 in) up from thebottom of the piston skirt.Oversize piston diameter:1st:82.185–82.205 mm(3.2356–3.2364 in)2nd:82.435–82.455 mm(3.2455–3.2463 in)TB69D50410Piston ring dimensionsTop and 2nd piston ring:B: 1.965–1.980 mm(0.0774–0.0780 in)T: 3.100–3.300 mm(0.1220–0.1299 in)Piston pin boss bore:19.904–19.915 mm(0.7836–0.7841 in)6F650450