Iron Stable

Harley-Davidson Softail Standard Big Bore Kits

Genuine HD big bore kits and aftermarket alternatives that fit the Softail Standard — all years. Select your year for exact fitment and pricing.

Select your year for exact fitment & prices

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Genuine Harley-Davidson (16)

Screamin' Eagle Stage II Bolt-On Power Kit

Genuine Harley-Davidson

Screamin' Eagle Stage II Bolt-On Power Kit

92500075A
£557.71Iron Pass £474.05£501.94View
3-7/8" Standard Bore Piston Kit

Genuine Harley-Davidson

3-7/8" Standard Bore Piston Kit

22144-08B
£381.08Iron Pass £323.92£342.97View
Screamin' Eagle 4-Inch Big Bore Conversion Kit

Genuine Harley-Davidson

Screamin' Eagle 4-Inch Big Bore Conversion Kit

92500039
£1350.96Iron Pass £1148.32£1215.86View
Big Bore Head Gasket Kit

Genuine Harley-Davidson

Big Bore Head Gasket Kit

16101-01
£56.76Iron Pass £48.25£51.08View
Screamin' Eagle 103 Stage IV Performance Kit

Genuine Harley-Davidson

Screamin' Eagle 103 Stage IV Performance Kit

27516-08F
£2903.40Iron Pass £2467.89£2613.06View
Screamin' Eagle 131CI Stage IV Performance Kit

Genuine Harley-Davidson

Screamin' Eagle 131CI Stage IV Performance Kit

92500095
£3779.28Iron Pass £3212.39£3401.35View
Screamin' Eagle MVA CNC Ported Cylinder Heads

Genuine Harley-Davidson

Screamin' Eagle MVA CNC Ported Cylinder Heads

16925-11
£1673.23Iron Pass £1422.25£1505.91View
Flat-Top Cast Pistons, 3-7/8" Std Bore, 1550cc

Genuine Harley-Davidson

Flat-Top Cast Pistons, 3-7/8" Std Bore, 1550cc

22851-99A
£269.53Iron Pass £229.10£242.58View
Screamin' Eagle Milwaukee-Eight 117 Stage IV Kit

Genuine Harley-Davidson

Screamin' Eagle Milwaukee-Eight 117 Stage IV Kit

92500073
£3045.94Iron Pass £2589.05£2741.35View
Stage II Bolt-On Performance Upgrade Kit

Genuine Harley-Davidson

Stage II Bolt-On Performance Upgrade Kit

92500058A
£526.72Iron Pass £447.71£474.05View
Screamin' Eagle Stage 2 Bolt-On Power Kit

Genuine Harley-Davidson

Screamin' Eagle Stage 2 Bolt-On Power Kit

92500074A
£557.71Iron Pass £474.05£501.94View
Screamin' Eagle 114CI Stage IV Upgrade Kit

Genuine Harley-Davidson

Screamin' Eagle 114CI Stage IV Upgrade Kit

92500062
£3045.94Iron Pass £2589.05£2741.35View
Screamin' Eagle Stage 2 Bolt-On Power Kit

Genuine Harley-Davidson

Screamin' Eagle Stage 2 Bolt-On Power Kit

92500047A
£526.72Iron Pass £447.71£474.05View
Screamin' Eagle 4-3/8 Inch Stroker Flywheel Assembly

Genuine Harley-Davidson

Screamin' Eagle 4-3/8 Inch Stroker Flywheel Assembly

23727-07A
£1424.50Iron Pass £1210.83£1282.05View
High-Compression Piston Kit, 4.060", Standard Bore

Genuine Harley-Davidson

High-Compression Piston Kit, 4.060", Standard Bore

22574-10
£435.83Iron Pass £370.46£392.25View
Screamin' Eagle 128CI Stage IV Performance Kit

Genuine Harley-Davidson

Screamin' Eagle 128CI Stage IV Performance Kit

92500094
£3779.28Iron Pass £3212.39£3401.35View

Aftermarket for your Softail Standard

Confirmed to fit your Softail Standard

Aftermarket big bore kits the supplier lists against the Softail Standard. Genuine Harley-Davidson is listed above, not here.

S&S 131CI & 136CI BIG BORE STROKER CYLINDERS FOR MILWAUKEE EIGHT

S&S Cycle

S&S 131CI & 136CI BIG BORE STROKER CYLINDERS FOR MILWAUKEE EIGHT

In stock
£1469.63Iron Pass £1396.15£1440.24View
S&S 131CI & 136CI BIG BORE STROKER CYLINDERS FOR MILWAUKEE EIGHT

S&S Cycle

S&S 131CI & 136CI BIG BORE STROKER CYLINDERS FOR MILWAUKEE EIGHT

In stock
£1469.63Iron Pass £1396.15£1440.24View
S&S 4.32" BIG BORE KITS FOR MILWAUKEE EIGHT

S&S Cycle

S&S 4.32" BIG BORE KITS FOR MILWAUKEE EIGHT

In stock
£1469.63Iron Pass £1396.15£1440.24View
S&S 4.32" BIG BORE KITS FOR MILWAUKEE EIGHT

S&S Cycle

S&S 4.32" BIG BORE KITS FOR MILWAUKEE EIGHT

In stock
£1546.10Iron Pass £1468.80£1515.18View
S&S 4.32" BIG BORE KITS FOR MILWAUKEE EIGHT

S&S Cycle

S&S 4.32" BIG BORE KITS FOR MILWAUKEE EIGHT

In stock
£1430.30Iron Pass £1358.79£1401.69View
S&S 4.32" BIG BORE KITS FOR MILWAUKEE EIGHT

S&S Cycle

S&S 4.32" BIG BORE KITS FOR MILWAUKEE EIGHT

In stock
£1469.63Iron Pass £1396.15£1440.24View
S&S 131CI & 136CI BIG BORE STROKER CYLINDERS FOR MILWAUKEE EIGHT

S&S Cycle

S&S 131CI & 136CI BIG BORE STROKER CYLINDERS FOR MILWAUKEE EIGHT

In stock
£1394.54Iron Pass £1324.81£1366.65View
S&S 131CI & 136CI BIG BORE STROKER CYLINDERS FOR MILWAUKEE EIGHT

S&S Cycle

S&S 131CI & 136CI BIG BORE STROKER CYLINDERS FOR MILWAUKEE EIGHT

In stock
£1546.10Iron Pass £1468.80£1515.18View
3 5/8" BIG BORE CYLINDERS AND PISTONS FOR EVOLUTION BIG TWIN

V-Twin

3 5/8" BIG BORE CYLINDERS AND PISTONS FOR EVOLUTION BIG TWIN

In stock
£439.90Iron Pass £378.31£395.91View
3 5/8" BIG BORE CYLINDERS AND PISTONS FOR EVOLUTION BIG TWIN

V-Twin

3 5/8" BIG BORE CYLINDERS AND PISTONS FOR EVOLUTION BIG TWIN

In stock
£331.78Iron Pass £285.33£298.60View
S&S 4.32" BIG BORE KITS FOR MILWAUKEE EIGHT

S&S Cycle

S&S 4.32" BIG BORE KITS FOR MILWAUKEE EIGHT

In stock
£1469.63Iron Pass £1396.15£1440.24View
S&S BIG BORE KITS FOR MILWAUKEE EIGHT

S&S Cycle

S&S BIG BORE KITS FOR MILWAUKEE EIGHT

In stock
£1524.32Iron Pass £1448.10£1493.83View

Identify the engine upgrade before comparing Stage kits

This category contains different levels of engine work. A shared Stage name does not mean the same starting displacement, cylinder heads, camshaft or calibration. Compare the exact kit contents with your existing engine and the riding character you want.

Select your year before choosing a kit. The 117-to-131 film applies to 92500146, not every 131-labelled or Stage IV product in this all-years grid.

A cam-chest upgrade is a different purchase

The catalogue also places Stage II Bolt-On Power Kit 92500075A here. Its description specifies opening the cam chest and a power delivery aimed at the middle and upper rev range. Do not read the category name as a promise that this kit includes larger cylinders or the complete Stage IV combination. Use its own parts list and installation requirements when planning the work.