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
8. Procedure
8.1 Assembly of the Engine - For information on the dismantling, inspection, and reassembly of the engine, see Annex A3 and the Yamaha RD-350B Engine Service Manual.
8.1.1 The following new parts are used for each test:
Two piston and ring assemblies, complete.
Two cylinder head gaskets.
Two cylinder base gaskets.
Two exhaust gaskets.
Two NGK B9HS spark plugs (or equivalent).
Two sets of breaker points.
8.1.1.1 It is desirable to fit breakerless ignition, in which case, the points are not required.
8.1.2 Cylinders may be used for two engine builds. Install Yamaha manufactured oversize pistons and ring sets for the second build. Hone cylinders and obtain piston clearances in accordance with A3.2.3 and A3.2.4. Use oversize pistons and rings in both cylinders of the second build.
8.2 Expected Life - It is recommended that the engine be rebuilt after ten complete tests (normally twenty evaluation runs) plus when the calibration run specified in 9.1 has been completed. The crankcase, crankshaft, rods, and associated seals and bearings shall be examined and replaced if necessary.
9. Procedure
9.1 Calibration Run - Every six months, run as specified in 9.3 with Reference Oil 606 in both cylinders. The ratings for both piston skirt varnish and second ring sticking shall be within 1.0 merit numbers in both cylinders. Invalidate tests where hot ring sticking or scuffing on the second ring in either cylinder is noted. Find and correct the reasons for test failure or invalidation, or both, before further testing.
9.2 Break-In - A new engine, or one that has been rebuilt as specified in 8.1 or 8.2, shall be broken in over a period of 2 h as specified in Table 1 using the same fuel and oil mixture in each cylinder as will be used in the immediately following calibration or test run. The power output specified is approximate and may vary by about +/- 5 %.
9.3 Test Procedure - Initially, run the benchmark reference oil in number one cylinder of the engine, and the non-reference oil in number two cylinder (the cylinder on your right when facing the intake side of the engine). Normally, run the test twice, exchanging the non-reference and reference oils between the cylinders. If hot ring sticking or scuff is observed on the reference oil piston, determine and correct the cause of the malfunction and rerun the test. If this occurs during the second run of a test, it is not necessary to repeat the first run.
NOTE 2 - If the test method is being used to satisfy a portion of Specification D4859, refer to the specification for possible exception to the above conditions.
9.3.1 Procedure - Before starting each running cycle, initially and after any shutdown, idle for 5 to 6 min at 2000 to 2400 r/min to warm up. Run the test on the cycle of Table 2, varying the cooling air flow to maintain the specified plug gasket temperature.
NOTE 3 - The exhaust temperature is not in itself a test parameter, but any change of 30°C (55°F) or more from the normal expected reading that cannot be explained by a known change in operating conditions will usually indicate a malfunction such as a change in the ventilation of the test cell or obstruction of the exhaust.
9.3.2 Observations - The temperatures specified in 9.3.1 shall be recorded continuously as specified by 6.2.5.1 and be logged at least twice per hour, and the cooling air stream varied as necessary to correct any tendency to drift. The crankshaft r/min, power output, fuel consumption, air to fuel ratio and ambient conditions is preferably recorded continuously and shall be logged at least twice per hour.
9.3.3 Preignition - A rapid (1 min or less) increase of 10°C (18°F) in the spark plug gasket temperature over the steady state level may constitute an incident of major preignition. Normally an increase in spark plug temperature and a decrease in engine power output accompany a preignition. If it is determined that a major preignition has occurred, remove the spark plug and retain it, labeled with the run number, the oil used, the cylinder number, the total test hours, and the hours on that plug to the nearest 0.1 h. Replace with a new plug. If major preignition occurs again with the non-reference oil, terminate the test and record a failure. If more than one major preignition occurs with the reference oil, stop the test to investigate and correct the problem before rerunning. Sudden temporary increases of 7°C (13°F) or more and less than 10°C (18°F) constitute minor preignition. These are logged and reported, but the test is not interrupted.
9.3.4 Other Spark Plug Malfunction - Spark plug problems of fouling or bridging are normally indicated by a loss of power accompanied by a decrease in the gasket temperature of the affected spark plug. The spark plug shall be replaced and labeled and the incident reported as specified in 9.3.3 for major preignition, after which the test is continued.
9.3.5 End of Test - Remove the cylinders and cylinder heads. Remove the pistons from the rods, but do not remove the rings from the grooves. Rate the following according to the procedures of Section 10:
Piston ring sticking.
Piston skirt varnish.
Piston crown deposits.
Cylinder head deposits.
Exhaust port blockage.
