ASTM D4857 Standard Test Method for Determination of the Ability of Lubricants to Minimize Ring Sticking and Piston Deposits in Two-Stroke-Cycle Gasoline Engines Other Than Outboards
10. Inspection and Rating of Engine Parts
10.1 Inspection - Inspection and rating should be performed as soon as possible after completion of the test, and shall be performed within 24 h of the end of the test. Do not leave the engine disassembled for more than two hours prior to inspection, as exposure to the atmosphere may change the condition of rings and deposits. Do not begin the disassembly until the engine has cooled to within 5°C (10°F) of ambient temperature.
10.1.1 Disassembly - Remove the exhaust system, cylinder heads, cylinders, and pistons from the engine. Do not remove the rings from the piston. Engine parts may be washed in hydrocarbon solvent or wiped with a soft cloth, but shall not otherwise be cleaned. Deposits that are removed by washing in hydrocarbon solvent or by wiping gently with a dry or hydrocarbon-solvent-wetted cloth are not considered for rating purposes.
10.2 Rating:
10.2.1 Piston ring sticking and piston skirt and land deposits are given in numerical rating from 10 (best) to 0 (worst). The condition of the cylinder bore is stated qualitatively, as is that of the combustion chamber surfaces (piston crown and cylinder head). Port plugging is rated as the mean percentage of exhaust port area blocked by carbon deposits. Preignition and spark plug fouling and whiskering are rated by the number of occurrences. These procedures are discussed in more detail in the balance of this section.
10.2.2 Piston Rings - Rating numbers are given according to the tightness of the ring in its groove and the number of circumferential degrees over which it is stuck. Each ring is rated and reported separately. The criteria are given as follows, and are shown graphically in Fig. 2.
10.2.2.1 Apply a correction of -2.45 to the reference oil second ring sticking result before comparing the non-reference oil second ring sticking result.
(1) 10 free - a ring that will move under gravity if the piston is turned with its axis horizontal. A slight touch to overcome static friction is permissible.
(2) 9.5 sluggish - the ring will not fall under its own weight, but yields to pressure from a finger or pencil point up to the amount required to compress the ring by half its width.
(3) 9.0-5.0 cold stuck - will not move under pressure but shows no evidence of blowby across its face, indicating that it is free when running. The ratings range from 9 for a ring that is cold stuck over 30° or less of its circumference to 5 for a ring cold stuck over 330 to 360°, as indicated by Fig. 2.
(4) 4.0-0.0 hot stuck - firmly stuck in its groove with evidence of blowby or scuff across its face. Any hot stuck ring is a failure for the oil, but a numerical rating is normally assigned, from 4 for a ring hot stuck over 30° or less to zero from a ring hot stuck over 330 to 360°.
10.2.3 Piston Skirt Varnish - Follow the CRC Manual No.14 (Varnish Rating) in allocating numbers from 10 (clean) to 0 (completely black). Rate the inlet and exhaust side of the piston separately, looking in the direction at right angles to the axis of the wrist pin.
10.2.4 Piston Crown - Describe the deposits by type, thickness, and location. A color photograph, oriented to the ports, may be provided.
10.2.5 Cylinder Head - As for the piston crown.
10.2.6 Exhaust Port Blocking - Report the percent of the total port area blocked by deposits. If this is greater than 10 %, photographs are required.
10.2.7 Piston Damage - Any occurrence of scuffing or scoring shall be reported as to extent and location.
10.2.8 Condition of the Cylinder Bore - Rate the inlet and exhaust sides separately. Report any varnish deposits by area covered and appearance. If the condition of the bore indicates scuffing or other lubricant-related damage, or is in any other way unusual, report it with appropriate description.
10.2.9 Spark Plugs - Report the condition of any spark plug removed during the test and the operating time as specified in 9.3.3.
10.2.10 Other Discrepancies - Any unusual wear or damage in any part of the engine shall be reported.
