(a) Water in fuel. Water may be present in fuel tank and carburetor. Drain and refill fuel tank and carburetor bowl.
(b) Incorrect valve tappet adjustment or sticky valves. Test (step b (1) below). Adjust tappets (par. [43]). (c) Defective ignition system. Refer to paragraph [32].
(d) Defective fuel system. Refer to paragraph [31].
(e) Weak and/or broken valve springs. Refer to higher authority.
(7) Spark Knock.
(a) Defective ignition system. Refer to paragraph [32].
(b) Excessive carbon deposits. Refer to step b (2) below.
(c) Defective fuel system. Refer to paragraph [31].
(d) Defective lubrication system. Refer to paragraph [30].
(8) Pounding and Excessive Metallic Noise.