The Harley-Davidson Sportster Uses 2 Different Types of Oil. Big Twin Uses 3 Types!

There are two types of lubrication for 4-stroke engines: wet sump and dry sump, and in the previous article we mentioned that Harley-Davidson uses a dry sump system. On top of that, in this article we will introduce the oil that lubricates the transmission. When you think of separate engine oil and transmission oil, you may think of 2-stroke engines, but there are some 4-stroke models where the engine and transmission are lubricated with separate oils.

It is not possible to say that the transmission is separate because it is a dry sump.

The transmission oil change is practiced on a 1997 Sportster 883, which is over 20 years old, so the intake system is carbureted and the engine is rigid mounted, but the crankcase and transmission lubrication system have not changed.

There are two types of lubrication systems for 4-stroke engines: wet sump, which circulates the oil in the oil pan in the crankcase, and dry sump, which collects the oil by pumping it from an oil tank located separately from the engine. Most motorcycles manufactured today use the wet sump system.

I introduced you to another point in the engine and transmission are lubricated with separate oils. This is one of the unique characteristics of Harley.

The same is true for 2-stroke engines, where the combustion and transmission chambers are separate, and the engine oil that burns and the oil that lubricates the clutch and transmission have different roles, so special oils are used.

In a four-stroke engine, the basic performance requirements for engine oil and transmission oil are not significantly different. This is evident in wet-sump engines, where the crankshaft and pistons are lubricated with the same oil as the transmission and clutch.

As for whether Harley's lubricate their engines and transmissions with different oils because they are dry sump, the examples of the Yamaha SR400 and Honda CB750 Fords, which are dry sump and lubricate their engines and transmissions with the same oil, show that this is not necessarily true.

A simple way to describe why the engine and transmission are lubricated with different oils might be to say that the engine and transmission cases are separate.

In Harley's Big Twin, Triumph before the introduction of the unit engine in the late 1950s, and Kawasaki W1 in Japan, the so-called engine part of the crankcase, which contains the cylinder head, cylinder and crankshaft, and the gearbox, which contains the clutch and transmission The power generated by the crankshaft was transmitted to the gearbox by the primary chain.

In contrast, the majority of today's motorcycle engines have the crankshaft and transmission in a single crankcase, and the power from the crank is transmitted by gears.

If the engine and transmission are separate units, this means that each requires its own oil for lubrication. In addition, the primary chain, which connects the crankshaft to the gearbox, also needs lubrication. This means that a Kawasaki W1 or Harley big twin needs three different oils: engine oil, transmission oil and primary oil.

Harleys differ between big twins and sportsters.

Harley-Davidson is known for its air-cooled 45° V-twin. Although many American models made in Japan have appeared in the past, the popularity of the original Harley, which continues to make its own progress, is still strong.

Harley-Davidson engines have traditionally been classified into two lines: Big Twin and Sportster. Both share the same engine format, a 45° V-twin with OHV valve drive, but differ in the lower engine and crankcase configuration.

In the Big Twin, the engine part, the gearbox and the primary chaincase are independent of each other, and these three units are independent of each other.

The Sportster, on the other hand, uses separate engine and transmission oils, but the crankcase is a combination of the engine, primary chain case and gearbox.

On the other hand, the crank chamber and the primary chain are lubricated with different oils in the integrated crankcase.

Specifically, there is a wet multi-disc clutch at the rear of the primary chain on the left side of the engine and a gearbox behind it. This chain, clutch and gearbox are lubricated with the same oil.

I believe that American models made in Japan are influenced by Harley-Davidson Sports to a greater or lesser extent, but none of them have a dry sump system and separate lubrication for transmission. I don't know if they judged that they didn't need to refer to it that much, or concluded that they could secure enough performance with wet sump, but at least Harley-Davidson, the originator of this engine type, inherited the method of lubricating engine and transmission with a different oil.

By the way, we've repeatedly said that Harley engines are dry sump lubricated, but there are exceptions: the liquid-cooled V-ROD, introduced in 2001, is wet sump, unlike the Big Twin and Sportster. The Street 750 is also wet sump, with the crankcase and gearbox completely integrated, so that both engine and gearbox are lubricated by a single type of oil. Since it is not a dry sump, there is no oil tank under the seat.

It may not be common to observe Harley-Davidson from a maintenance point of view, but if we classify them in terms of oil maintenance, it can be said that the three types of engines, Big Twin, Sportster and Street 750, have different lubrication methods and different oil requirements. It is a characteristic point.

You don't need to remove the primary cover to change the transmission oil, but just for reference of primary drive by primary chain. Although it is built into the crankcase, the Honda CB750 also used a chain to transmit power between the crankshaft and main shaft.
 

I can't find the oil inlet on the primary cover.

The transmission oil drain bolt is located at the rear of the crankcase. The head of the bolt is low, so it is best to use a spectacle wrench to loosen it instead of a wrench which is easy to remove.

There is a magnet on the end of the drain bolt to collect the iron dust in the primary case and gearbox. Wipe it off with a rag and then clean it with parts cleaner.

When you change the transmission oil on your Sportster, pull out the drain plug on the left side of the engine to drain the old oil. Inside this primary cover sits the metal chain that connects the crankshaft to the clutch shell.

While the drive sprocket is connected to the rear tire by a cogged belt, which has an overwhelming advantage in terms of maintenance, the primary is an old-fashioned metal chain, which has a long history, but this chain is constantly lubricated in the case by being immersed in transmission oil, so it requires almost no maintenance. The chain is always lubricated by the transmission oil in the case, so it needs almost no maintenance.

The drain bolt is located at the bottom of the primary chain, but since the primary case on the Sportster is integral to the gearbox, the oil that lubricates the transmission also comes out of the drain with it. Unlike engine oil, which is exposed to high temperatures around the combustion chambers, transmission oil, which is sheared off by the clutch and gears, seems to have less of a tendency to degrade to black even with high mileage. Instead, it tends to have a lot of metal powder from the friction of the transmission, so it is important to wipe off the dirt that adheres to the magnet at the tip of the drain bolt.

For the 1997 Sportster, the specified transmission oil capacity is 946ml for both the 883 and 1200. The factory oil used to distinguish between engine and transmission oil, but now the base oil is a synthetic oil. The oil that can be used for both engine and transmission has been released.

The original oil that can be used to lubricate the primary chain and transmission for Sportsters has also evolved from the old trans fluid to Formula Plus.

Of course, genuine oil is safe, but you can also choose your favorite brand of normal 4 stroke oil to lubricate your transmission and clutch. However, in that case, it is safe to choose 20W50 of the same viscosity as genuine oil, which is considered to be harder in the sense of Japanese motorcycles.

When draining the old transmission oil, it's somewhat obvious because there is a drain bolt on the bottom of the engine, but when filling, the Sportster is confused as to where to start. Generally speaking, there should be a screw-in cap on the primary cover, but I can't find it anywhere.

The oil is poured from the gap of the clutch release (clutch outer ramp in Harley) after removing the large inspection cover at the rear of the primary cover. It may be a culture shock for riders who have only touched Japanese motorcycles to pour oil from here.

Also, because this opening is located low in the cover, if the motorcycle body is tilted to the left, the oil may overflow from the cover before it reaches the specified amount of 946ml, so it is important to keep the motorcycle body vertical when filling the oil.

Transmission oil tends to be checked and changed less frequently than engine oil, but the clutch and primary chain, which receive the torque of the V-twin engine, need to be lubricated by good quality oil. If you want to make your transmission last longer, we recommend you to change it as soon as possible.

Remove the clutch inspection cover at the rear of the primary cover in order to fill the transmission oil. The large diameter O-ring on the inside of the cover is an important part to prevent oil leakage as well as the O-ring of the filler cap, so it should be replaced when hardening or deterioration is observed.

Oil is injected through the opening of the clutch release on Japanese motorcycles and the outer ramp on Harleys. The clutch spring seen at the back of the opening is diaphragm type, and the lower edge of the spring becomes the oil level when the body is upright.
 

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