Monster Motor | A Look Inside Harley's 120R Engine

31 The engine is outfitted with SE lifters that are precision-machined and have a specific design that allows the lifters to move in a direct linear path. A roller crown design ensures constant contact with the cam lobes. On the left is an OE lifter, on the right is the SE lifter.

32 SE Perfect Fit Pushrods are also used in the 120R. The pushrods are 0.030-inch over OE length to work with the 266E cam specs and they feature a lighter weight (than adjustable pushrods), one-piece tapered design.

33 With the lifters in place, the pushrods were then installed along with the head gasket. The pushrods are marked with a white mark and a blue mark so that the technician installs them correctly.

34 Next, the cam cover was installed. The engine comes with a special SE 120R timing cover.

35 And one of the last steps in the assembly of the 120R is the installation of the rocker boxes. OE rocker boxes are used, however, the lower rocker box covers are machined to provide for valve spring collar clearance. Once the rocker boxes are torqued the engine is cold tested to ensure everything is working properly and within spec.

36 The engine is then hooked up to a crane, and moved over to a computer station.

37 The technician at this station inputs the information associated with the engine into the computer and a partial VIN is then stamped into left side of the case. The engine is now complete and ready to be packaged up and shipped to an eagerly waiting customer at a dealership…

38 …like this engine that was shipped to a customer at our local Anaheim-Fullerton Harley dealership. While the owner liked the look of the black and chrome finish, he wanted an all-black engine. So as soon as his 120R arrived he had the dealership send rocker boxes, pushrod tubes, and cam cover out to get covered in black powdercoat.

39 For his engine the owner also picked up the SE Pro High-Flow 58mm EFI Throttle Body, SE Pro High-Flow intake manifold, and SE Pro High-Flow injectors. The throttle body is precision machined and then polished and when matched with the High-Flow intake it provides increased airflow and air velocity into the engine. The High-Flow injectors provide 25 percent more fuel than their OE counterparts. They deliver fuel at a rate of 4.9 grams per second that helps create better combustion with the increased air.

40 The SE 120R was dropped into this not-so-subtle 2006 Dyna Street Bob. Needless to say, the owner isn’t shy about his bikes or their horsepower.

41 After the engine was installed the bike was run on the dyno where it produced 134.47 hp and 132.55 lb-ft of torque, definitely a major increase in power over the OE 88ci engine that was in the Dyna. With some tweaking and precise tuning, even more power could probably be squeezed out of the 120ci engine. Putting this kind of power into the 670-pound Dyna turns it into a completely different animal that’s hard to keep on two wheels. And it makes for some fun times at the drag strip. While this is strictly a race-only engine, I asked our H-D contacts about the possibility of the SE 120R eventually being a street-legal option. Harley is very tight-lipped about any future products and wouldn’t provide any comments either way on the matter. During my time at the POC it was very evident that the company has put a lot of time, money, effort, and manpower into this engine. I just hope we get to see some variation of a street-legal 120ci engine from the Factory put into a CVO or production model s