0913195 JOHNSON PLUG

Illustration 1 g03383792The cylinder block is the main housing of the engine. The cylinders do not have liners, but the walls are honed.
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(1) Injection Nozzle
(2) Glow Plug
(3) Combustion Chamber
(4) PistonFuel is injected at the center of the cylinder. Glow plugs are utilized to aid starting in cold temperatures.Gear Train
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(5) Fuel Pump Gear
(6) Idler Gear
(7) Camshaft Gear
(8) Crankshaft Gear
(9) Oil Pump GearThe crankshaft drives oil pump gear (9) an idler gear (6). The idler gear drives the fuel pump gear (5) and the camshaft gear (7).Each gear has a mating mark inscribed on the gear for proper assembly.Rocker Arm
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(10) Rocker Arm Shaft
(11) Rocker Arm
(12) Exhaust Valve
(13) Intake Valve
(14) Bridge Arm
(15) Push Rod
(16) Adjusting ScrewThe rocker arms are mounted on a rocker arm shaft at the top of the engine.When the push rods move up, the mating rocker arm is moved down, contacting the valve stem tip and opening the valve.These engines, two intake and two exhaust valves per cylinder, the rocker arm contacts a bridge arm instead of the valve stem tip. The bridge arm then contacts both intake or both exhaust valves and causes two valves to open simultaneously.Pressurized oil flows through the rocker arm shaft. Passages are drilled into the rocker arm shaft, which allows oil to flow into the rocker arm bushing.Piston
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(17) Concave Head PistonThe reciprocating motion of a piston in the engine cylinder creates the forces for the suction, compression, power, and exhaust cycles.To be strong yet light, pistons are constructed of cast iron or aluminum alloys. Reinforcing ribs are used to keep the piston as light as possible.The piston lands are the areas between the ring grooves which hold and support the piston rings in the grooves. A fine groove called a heat dam is provided on the top land to protect the top ring from high temperatures.The skirt of the piston is the outside part below the ring grooves. The piston is kept in alignment by the skirt.The piston is kept in alignment by the skirt. The piston skirt has a layer of molybdenum disulfide, which decreases the piston slap noise.The molybdenum disulfide is a solid lubricant, like Graphite or Teflon. This material helps not to wear the metal even with little lube oil.Note: A 0.25 mm oversized piston is available. Refer to Specifications, Cylinder Block for further information.Piston Rings
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(18) Top Compression Ring
(19) Second Compression Ring
(20) Oil Control Piston RingThere are three piston rings. The top two are compression rings that prevent gases from leaking by the piston. The third ring is the oil control ring and is to wipe oil from the cylinder walls.Note: A 0.25 mm oversized piston rings are available. Refer to Specifications, Cylinder Block for further information.Connecting Rod
Illustration 7 g06135183
(21) Two-piece Small End Bushing
(22) Connecting Rod
(23) Crankpin BearingThe large end of connecting rod has a crankpin bearing (split type) and the small end has a small end bushing (solid type).The connecting rod and the connecting rod cap will have an etched Number (X) on the side. The number on the connecting rod and the connecting rod cap must match. Do not reuse the connecting rod bolts.Ensure that the connecting rod and the connecting rod cap are marked for the correct cylinder number. 0.2 mm (0.008 inch) and 0.4 mm (0.015 inch) oversized crank bearings are available. Refer to Specifications, Crankshaft for more information.