This is a 25,000-mile engine from a late-model Honda CBR600RR. I am going to remove all the parts from the engine and identify them as I go. These basic components are common to many inline-fours that power current Japanese sportbikes.
1. You’ve heard of “stick” coils. This is the ignition coil—there are four of them—that steps up the 12 volts from the battery to 25,000 volts or more to jump a spark across the plug deep inside the cylinder head. They are used nowadays because they keep radio frequency shielded down inside the engine.
2. This suitcase-looking affair is the airbox. It also holds the air filter. Air from forward-facing intakes comes in through large holes. The interesting thing about this particular piece of Samsonite is that it has four fuel injectors in it. If we had a magnifying glass, we would see each one has 12 tiny holes to assist in atomizing the fuel. If you could see down inside, you would see the intake bells for the fuel injectors. These parts smooth the entry of air into the injectors. There are four of these because there are four cylinders.
3. This is the throttle-body assembly. Each throttle body has a butterfly valve, which opens to let air into the engine and closes for idle. Each has its own fuel injector, so there are four injectors close to the engine and four more on top of each intake located in the airbox.
4. Now I’m going to take off the cylinder-head cover. This aluminum part below it is the cylinder head. It contains the valves and the camshafts that operate them. The bright fasteners in the front connect the exhaust system to the four exhaust ports. Air and fuel in at the back, exhaust out at the front.
5. The business end of the cylinder head is the valves. You can see the spark plugs are located in the center of each chamber. The camshafts are driven by a silent chain, which is confined between two damper blades that prevent the free run of the chain from vibrating. A piston in each of the four cylinders would normally be connected to the crankshaft by means of an aptly named connecting rod.
6. The next thing I’m going to remove is the clutch cover. The clutch is behind this large, round bulge. The crankshaft centerline is directly in front of it. I’ve already removed the crankshaft because, like removing the pistons, it is a time-consuming operation. A sensor reads the rotation of a toothed wheel on the crankshaft that reports to the engine-control unit the position of the crankshaft, how fast it’s turning, and which piston is in which position. The spin-on oil filter is found on the front of the engine.
7. A deep aluminum oil sump is at the bottom of the engine. That is where the engine oil is kept. This is not a tremendously heavy unit, particularly with most of the parts removed from it. Oil is supplied to the crankshaft and other moving parts by an oil pump. Once that oil has done its job, gravity returns it to the sump, which is 3mm thick and hardly weighs anything.
8. A rotating assembly of magnets is located on one end of the crankshaft. Inside this cover is a set of iron poles with wire wound around them. As the magnets sweep past those poles, they cause changes in the magnetization, which generates power in the coils. In the old days, all an engine needed was a magneto to supply spark, but modern engines have so much electrical gear on them that more power is required.
9. This is the lower crankcase. The crankshaft spins in five plain bearings, which take the form of thin shells lined with a soft material. There are holes to supply oil, and each bearing shell has a groove.
10. Here is the upper crankcase, showing the matching upper halves of the crankshaft bearings. Each cylinder’s bore is hard-plated directly on aluminum. This eliminates the insulating effect of the iron liners that were previously used. Old-timers like those iron liners because they can be rebored. This engine can’t be rebored. On the other hand, this engine takes care of itself so well that at 25,000 miles, it hasn’t needed any help.