In The Shop: Twin Cam B Motor Counterbalance Assembly

Softail Twin Cam B Motor Counterbalance Assembly

The bottom end of a Softail Twin Cam B motor is a little bit different than the typical Big Twin bottom end. Most of the bottom end is the same but with the exception of a balance assembly.

Most of the balance assembly is located on the left (drive) side of the crank, with balancing counter weights positioned in front and behind the flywheels. B motors can be easily identified because of their elongated shape which is necessary to fit the balance assembly.

Recently, In The Shop, we had the opportunity to rebuild two B motors in the same week. Both motors were severely damaged. Stock flywheels were removed and replaced with S&S flywheels. Of course, main bearings balance assembly bearings, and cam compartment bearings were also replaced.

Before being able to split the crankcase halves, the top end and cam compartment need to be disassembled. The stator needs to be carefully removed from the left crankcase half. This work can be performed with the entire engine still cradled in the motorcycle frame or with the engine removed and on the bench.

We prefer to begin engine disassembly with the engine still mounted in the frame. Once we are down to only a crankcase assembly, we remove the bolts that secure the crankcase to the transmission case, we remove the two front motor mounts, and carefully lift the crankcase assembly out of the frame and onto the bench. There will be residual oil in the bottom of the crankcase. Before splitting the cases, we like to tip the motor on our breakdown bench. We support it upside-down with blocks of wood and let drain overnight or while we clean up top end parts and hardware. Take extra care while handling an assembled bottom end. It is heavy. Cylinder studs can be easily damaged or bent if mishandled.

Once crankcase hardware is removed, the case halves can be separated and the balance assembly will be accessible. Follow the specific factory service manual instructions for proper rebuild procedures, tools, and safety.

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One Response to “In The Shop: Twin Cam B Motor Counterbalance Assembly”

  1. Benito g altiery

    Verry cool I’m interested in learning all about these motors