• Huge displacement increase means huge power increase
  Stock crankcases, cylinder heads, oil pump, and cam cover can be reused, saving hundreds of dollars
• Original engine serial numbers are retained
• Gear drive S&S 640 Easy Start Cams included
• Black powder-coat finish heads match factory finish, giving bike a "sleeper" advantage
• .045" MLS (multi-layered steel) head gaskets
• Requires crankcase boring
• Adds .096" to engine height
• Kits with S&S® heads use stock length manifolds (S&S size 410)
• Kit includes S&S® Super Stock® 91cc Cylinder Heads
• Flat top forged pistons w/10.8:1 Compression Ratio 
• 4 5/8" Stroke
• 4 1/8" Bore
• 5.013" Cylinder length
• Made in the U.S.A.
• Not for Twin Cooled models

NOTE: This project requires a skilled technician. It is the responsibility of the person assembling the parts to check all clearances and assembly specifications

NOTES:

Stock crankcases need to be machined to accept new cylinders.

S&S Easy Start Cams save you money – no need to buy compression releases or S&S rocker covers.

Note when using 1999-'06 chain drive cams: For lifts over .510", S&S strongly recommends that the stock chain drive be upgraded to the S&S gear drive or to the H-D® #25284-08 or #25284-11 hybrid plate. This kit updates the problematic spring loaded chain tensioners to more reliable hydraulic tensioners and also upgrades the oil pump.

Main Bearing Note: S&S flywheel assemblies included in a 124” S&S Hot Set Up Kit® for 1999-'15 big twin engines are designed for use with Timken® sprocket shaft bearings. They will fit directly in stock 1999-’02 Harley-Davidson® crankcases and in all S&S crankcases for 1999-'15 Big Twin engines, with no modifications. However, stock 2003 and later engines use a roller type bearing for the sprocket shaft, and will require modification.

Due to the amount of power these engines produce with an S&S Hot Set Up Kit, S&S strongly recommends retrofitting 2003-'15 model crankcases to accept a Timken sprocket shaft bearing. A Timken conversion sleeve such as Screamin' Eagle® #34822-08 or Jim's® #956 may be used. A charging system spacer for 1999-'02 model year is also required. 

If you choose not to convert your crankcases to a Timken sprocket shaft bearing, S&S flywheels may be used in 2003 and later engines with the installation of the
Harley-Davidson® bearing kit #24004-03B. This bearing kit adapts the S&S sprocket shaft to be compatible with stock roller type bearings. Verify that the bearing kit contains the 24604-00D or 24607-07 sprocket shaft bearing. Do not use a 24604-00, 24604-00A, 24604-00B or 24604-00C bearing. Please be advised that if this type of bearing is used, sprocket shaft bearing failure WILL NOT be covered under warranty.

Kits with S&S heads are machined special to compensate for engine height change to accommodate a stock length manifold. 

The Air Resources Board (ARB) does not permit the use of aftermarket emission-related parts that alter the air/fuel ratio of an emission-controlled vehicle. Due to these legal restrictions this part cannot be shipped to California.