Crankshafts for Harley-Davidson Evolution Sportster

Harley-Davidson Evolution Sportster crankshafts

Brief technical history

Since there are a number of variations of the standard OEM crankshaft assembly for this model, plus the Buell and XR1200 variants, a brief technical history would be appropriate.

When Harley introduced the Evolution Sportster as a replacement for the Ironhead in 1986, they changed the construction of the crankshaft, even though the stroke remained the same at 3 13/16". Initially introduced as an 883 and 1100 (same stroke, different bore), the Ironhead cast Iron flywheels, with seperate hardened steel mainshafts, gave way to forged steel flywheels with integral shafts. A press fit inner bearing race was, and still is, used to provide the bearing surface for the pinion side (right hand) main bearing. The same large Torrington needle bearing used since '77 was also retained, as was the splined drive for the oil pump and camshaft pinion gear.

The connecting rods (first used on the XR1000) are shorter than the Ironhead, 6.926" versus 7.440" centres, but the same tapered crankpin was used, thus allowing the rods to be readily replaced, or rebuilt, as before, using traditional rebuilding techniques.

For 1987 Harley changed the pinion bearing for a seperate outer race (which has to be line lapped) and a set of caged rollers. When the 1100 was discontinued in favour of the 1200 for 1988, they went away from the splined oil pump and pinion gear drive, and replaced this with a cheaper to produce, but potentially weaker, straight shaft with a single location key. This arrangement is still used, but relies on the end clamping load of the pinion nut to provide the drive.

The 5 speed crank, introduced for 1991, is of similar construction, but with a longer sprocket shaft (left hand) to accomodate the relocated alternator. So, prior to the introduction of the press fit crank in 2000, all of these cranks are officialy deemed rebuildable, and rod sets, races, crankpins, and bearings are available from Harley-Davidson, as well as the aftermarket. However, because the shafts are integral with the flywheels, any damage to the shafts requires complete crankshaft replacement. The most common cause of this is the sprocket nut coming loose and allowing the sprocket and/or alternator rotor to chatter on the splines. Another point to note is that, for any given year group, there is a different part number for the 883 and 1100 and for the 883 and 1200. The parts used in any year group are the same, but the flywheels are balanced for the different piston weights, and this can be changed during rebuilding.

Sprocket side Harley-Davidson Evolution Sportster flywheels.

This picture shows the difference in construction of the sprocket side (left hand) flywheels. To the left is an Ironhead flywheel. Made of cast iron, it has a seperate, hardened steel, shaft. In the middle is a 4 speed Evolution flywheel. Notice that the shaft is integral with the steel wheel. And to the right is a 5 speed flywheel. The construction is the same as the 4 speed, but the shaft is longer to accept the alternator, which was sensibly relocated from inside the rear of the clutch basket, to the end of the crankshaft (as with the Big Twins from 1970 onwards).

Early and late pinion side flywheels.

On the left is the pinion side (right hand) flywheel from a 1986 1100. This uses the stronger, splined, oil pump and pinion gear drive carried over from the Ironhead. The pinion bearing inner race, which has no retaining ring groove, is to suit the Torrington bearing which also carried over from the '77 up Ironhead On the right is a 5 speed flywheel and this uses the still current inner bearing race, as well as the, cheaper to produce, plain shaft with a location key.

For the 2000 model year Harley switched to a press fit construction, the same as the Twin Cam. These are a completely different construction, still utilising integral mainshafts, but using a parallel crankpin. Harley consider these non rebuildable, and as such, offer no spare parts, just complete assemblies. Interestingly, there are no seperate part numbers for the 883 and 1200 as they are not balanced! We can, however, rebuild these here, as we have had crankpins and thrust washers made, and use modified Big Twin rod races for the slightly wider rear con rod. The big end bearing roller assembly and wrist pin bushes are the same as the earlier type.

press fit Sportster crankshaft.

The 2000-2003 press fit Harley-Davidson Sportster crankshafts are now rebuildable here. Using a combination of parts from earlier models, modified Big Twin bearing races, and specially manufactured crankpins and thrust washers, we rebuild these, even though Harley have not chosen to offer these parts.. We also balance them!

For the 2004 model year, with the introduction of the rubber mounted Sportster, there was a major (and very effective) engine redesign. Whilst still a press fit assembly, these newer crankshafts use the sprocket side bearing from the Twin Cam. There are currently no aftermarket alternatives, although complete OEM assemblies are available through us. We will be doing our own R&D to determine the viability of rebuilding these.

Crankshafts for Harley-Davidson Evolution Sportster

S&S crankshafts for Harley-Davidson Evolution Sportster.

S&S crankshafts for Harley-Davidson Evolution Sportster.

These S&S crankshafts, which we can supply either assembled by S&S, or modified and assembled here, are very strong and durable, as well as completely rebuildable. They use heat treated forged steel flywheels, seperate hardened steel mainshafts, and stronger connecting rods. The mainshafts use a much larger taper than the old OEM Ironhead design, which greatly improves rigidity. They use the far superior 1986 splined pinion shaft design, so a new oil pump drive gear and pinion gear is also required, but this completely eliminates the possibility of the pinion gear shifting and changing the valve timing.

These are available to fit the 86-90 4 speed and the 91-03 5 speed engines, but not the 04 up rubbermount models. We can supply these as a stock stroke replacement with regular S&S rods, or as a component part of a big bore stroker kit for one of our larger capacity high performance upgrades.

Please note that the stroker versions have longer connecting rods (7.113 versus 6.926), and require taller cylinders, adjustable pushrods, a wider intake manifold and different top motor mounts. All of these extra parts can be included in our kits. At this level we are into professional engine building territory, and as such we can carry out all associated work, including machining and tuning.

S&S crankpins for Harley-Davidson Evolution Sportster

S&S crankpins for Harley-Davidson Evolution Sportster

The crankpin is one of the most highly stressed parts in the engine, it also causes the most damage if it fails, and requires a complete strip down and rebuild to replace it. Not surprisingly we won't cut any corners with the quality of this component. The S&S crankpin also comes supplied with new heat treated nuts, and we have this reliable part in oversizes to suit the rod bearings and race sizing method that we choose to use when rebuilding the connecting rods.


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