In our Sportster Buyer’s Guide video, Mike reminds us that in 2004, the Sportster engine, crankcase, and transmission went through considerable changes.
The most noteworthy change is that there is no longer a trap door behind the primary drive (left-side case) where the transmission gear set can be accessed.
Previously, we could have the Sportster gear set on the bench after only about an hour of disassembly. Disassembly would typically consist of removing the front pulley, disassembly and removal of the primary drive, and removal of the transmission trap door hardware. Since 2004, the only way to access the transmission is by separating the two crankcase halves.
This is a big undertaking and is very labor intensive. In fact, if you can not perform the labor yourself, it may be a better option to spend money on a used Sportster engine/transmission assembly or to buy another used Sportster all together. Of course, decisions like this depend on a number of factors, and if the motorcycle has sentimental value, you will be fixing the motorcycle regardless.
Recently, we had a custom bike come in the shop that was built with a rigid aftermarket frame and was powered by a 2005 Sportster engine/transmission/drive. The issue was that the engine was smoking badly. We diagnosed that the aftermarket oil tank that was being utilized had been plumbed incorrectly. This starved the engine’s top end for oil which, in short time, wiped out the rear piston & cylinder, with the front being close behind. Debris was spread throughout the engine, so we needed to plan for a complete engine rebuild. There was considerable debris in the cam compartment, so we knew that we would need to thoroughly clean out the flywheel compartment as well as replace the main bearings.
We thought this job would be a good example & visual of what the 2004 and newer Sportster engine & transmission look like once stripped down.
Here are some pictures of the disassembly and some of the motor out and on a bench.
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How does the gearbox get lubricant from the primary case? I don't see any holes for the oil to seep into it. My 2019 irons gearbox often sound's like it hasn't any in.