Harley-Davidson Crankshaft Rebuilding

Harley-Davidson taper shaft crankshaft repair

All Harley taper shaft cranks (pre Twin Cam Big Twins and pre 2000 Sportster) are designed to be rebuilt.

Harley crankshaft rebuilding

Crankshaft run out is checked with a set of modified inspection bench centres.

To this end we have developed and constructed specialised truing and measuring fixtures to enable us to offer this service. Unless there are any machining errors in the original flywheel manufacturing process, we can typically true these assemblies to .001 or less, which, in conjunction with our crank balancing, will give a smoother running engine and improved longevity.

Harley crankshaft rebuilding

Sprocket shaft, pinion shaft, and crankpin nuts must be accurately torqued. On some flywheel sets this can be as high as 450ft/lbs. We have developed and built our own system to do this using a clamping system and a torque multiplier, fixtured to a heavy cast iron bench.

We also rebuild, and supply, S&S crankshaft assemblies and can also machine damaged S&S flywheels to accept bronze thrustwashers.

Indian 100 crankshaft rebuild

The Indian 100 crankshaft assemblies are very similar to Harley's Evolution Big Twins'.

Harley-Davidson press fit crankshaft repair

Harley switched to a parallel crank pin for the Twin Cam engines in 1999 and for the Sportsters and Buells in 2000. These crankshafts are pressed together, and despite having manufactured well over a million of these, Harley do not sell replacement parts to repair them. The big names in the aftermarket, which we normally associate with crankshaft parts, have also chosen not to offer these needed parts either. This is not new technology to Harley, as the XR750 race engines are constructed this way. (We have also built these cranks)

Machining XR750 flywheels

Machining XR750 flywheels

Pressing XR750 flywheels together

Pressing XR750 flywheels together

Two XR750 crankshafts, balanced, assembled, and trued here.

Two XR750 crankshafts, balanced, assembled, and trued here.

Whilst complete aftermarket assemblies are available for the Twin Cams, we have had bikes in here with badly shifted flywheels and excessive big end clearances using these cranks, which has made us reluctant to offer them. The later OEM Twin cam cranks are also getting a bit of a reputation for excessive runout which damages both the oil pump and the cam support plate. We've also had brand new replacement OEM cranks that we’ve had to send back due to not being correctly trued in the first place.

As a result of this, and the fact that the older (only now manufactured as spare parts) assemblies are very expensive, we have been doing our own R&D to find a solution.

We have now sourced high quality rod races, bearings, thrust washers, and crankpins, which allows us to rebuild the 2000-2003 press fit Sportster crankshafts. We are still doing our own R&D for the later rubbermount XL cranks.

Harley connecting rods repaired, and all newly sourced components ready to reassemble a 2001 Sportster crankshaft

Harley connecting rods repaired, and all newly sourced components ready to reassemble a 2001 Sportster crankshaft

Finished Harley Sportster crankshaft repair.

Finished Harley Sportster crankshaft repair.

For the Twin Cam engine we are now supplying new Darkhorse crankshaft assemblies. These are renowned as being the best in the business, and are USA made. They have hardened steel plugs in the crankpins (like the XR750 racing cranks), which strengthens the interference fit, and are welded. We have these available in different strokes to suit our reliable, high performance Harley Twin Cam engine builds. Naturally, this is also by far the best reliability option for any standard rebuild.

Darkhorse Harley Twin Cam crankshaft

Darkhorse Harley Twin Cam crankshaft. These are the best Twin Cam press fit crankshafts available. Notice the stronger H-beam connecting rods, and the proplugged and welded crankpin. This crank has also been balanced to suit our Head Quarters forged pistons.

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