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Harley Engine

Harley Engine

Harley Engine

Harley Bike Engine Parts at JJ Motorsports

Rebuild and boost your Harley's engine with premium parts from JJ Motorsports. Our inventory features complete gasket sets, piston kits, oil filters, pushrod tubes, and coolers designed for maximum strength, leak-free sealing, and high-performance in extreme conditions. Compatible with Big Twins, Softail, Touring, and more, these components support top-end overhauls, oil management, and durability for street rides or custom builds.

Shop trusted brands like Drag Specialties for magnetic filters and Wiseco for forged pistons. Explore related categories such as Harley air and fuel for carb tuning or Harley drivetrain for transmission upgrades.

Top Harley Engine Products

Browse our in-stock inventory below with same-day shipping and expert support. Questions? Contact us for fitment advice!

  • Product
  • Qty in Cart
  • Quantity
  • Price
  • Subtotal
  • COMETIC Trans Gasket - Big Twin C9469

    COMETIC Trans Gasket - Big Twin C9469

    COMETIC

    $81.85
    High quality, application specific materials give a long and reliable life, Kit includes all necessary gaskets, seals and O-rings needed for each application, Made in the U.S.A.
    09340824
    SKU:
    09340824
    Availability:
    Ships Same Business Day
    Weight:
    1.22 LBS
    TYPE:
    TRANSMISSION
    UNITS:
    KIT
    RIDING STYLE:
    STREET
    PRODUCT NAME:
    GASKET KIT
    $81.85
    Qty in Cart: 0
    Quantity:
    Price:
    $81.85
    Subtotal:
  • COMETIC Trans Gasket - Twin Cam C9639

    COMETIC Trans Gasket - Twin Cam C9639

    COMETIC

    $47.20
    High quality, application specific materials give a long and reliable life, Kit includes all necessary gaskets, seals and O-rings needed for each application, Made in the U.S.A.
    09340826
    SKU:
    09340826
    Availability:
    Ships Same Business Day
    Weight:
    0.31 LBS
    TYPE:
    TRANSMISSION
    UNITS:
    KIT
    RIDING STYLE:
    STREET
    PRODUCT NAME:
    GASKET KIT
    $47.20
    Qty in Cart: 0
    Quantity:
    Price:
    $47.20
    Subtotal:
  • COMETIC Trans Gasket - Big Twin C9464F

    COMETIC Trans Gasket - Big Twin C9464F

    COMETIC

    $45.10
    High quality, application specific materials give a long and reliable life, Kit includes all necessary gaskets, seals and O-rings needed for each application, Made in the U.S.A.
    09340827
    SKU:
    09340827
    Availability:
    Ships Same Business Day
    Weight:
    0.44 LBS
    RIDING STYLE:
    STREET
    PRODUCT NAME:
    GASKET KIT
    TYPE:
    TRANSMISSION
    UNITS:
    KIT
    Qty in Cart: 0
    Quantity:
    Price:
    $45.10
    Subtotal:
  • COMETIC Trans Gasket - 4 Speed C9465

    COMETIC Trans Gasket - 4 Speed C9465

    COMETIC

    $67.15
    High quality, application specific materials give a long and reliable life, Kit includes all necessary gaskets, seals and O-rings needed for each application, Made in the U.S.A.
    09340828
    SKU:
    09340828
    Availability:
    Ships Same Business Day
    Weight:
    0.39 LBS
    UNITS:
    KIT
    PRODUCT NAME:
    GASKET KIT
    RIDING STYLE:
    STREET
    STYLE:
    4-SPEED
    TYPE:
    TRANSMISSION
    $67.15
    Qty in Cart: 0
    Quantity:
    Price:
    $67.15
    Subtotal:
  • COMETIC One Piece Rocker Base - Evo C9865

    COMETIC One Piece Rocker Base - Evo C9865

    COMETIC

    $22.00
    Viton gaskets feature a stainless steel core with a .001"-thick coating of Viton rubber on both sides., Made in the U.S.A.
    09340001
    SKU:
    09340001
    Availability:
    Ships Same Business Day
    Weight:
    0.15 LBS
    PRODUCT NAME:
    GASKET
    UNITS:
    PAIR
    RIDING STYLE:
    STREET
    THICKNESS:
    0,51 MM (0,020')
    THICKNESS IMPERIAL:
    0,020'
    THICKNESS METRIC:
    0.51 MM
    MATERIAL:
    STEEL
    MATERIAL:
    VITON
    TYPE:
    ROCKER BOX
    $22.00
    Qty in Cart: 0
    Quantity:
    Price:
    $22.00
    Subtotal:
  • COMETIC Base Gasket - Evo - 1340 - .020" C9870

    COMETIC Base Gasket - Evo - 1340 - .020" C9870

    COMETIC

    $33.55
    Outer layers are embossed and coated on both sides with Viton to meet the demands of a variety of harsh sealing environments, load conditions, and surface finishes, MLS (Multi-Layer Steel) head gaskets promote an even torque load across the gasket...
    09340004
    SKU:
    09340004
    Availability:
    Ships Same Business Day
    Weight:
    0.10 LBS
    MATERIAL:
    RUBBER
    MATERIAL:
    STEEL
    THICKNESS:
    0,51 MM (0,020')
    TYPE:
    CYLINDER BASE
    UNITS:
    PAIR
    PRODUCT NAME:
    GASKET
    STYLE:
    STANDARD
    THICKNESS METRIC:
    0.51 MM
    BORE SIZE IMPERIAL:
    3.8125'
    RIDING STYLE:
    STREET
    THICKNESS IMPERIAL:
    0,020'
    $33.55
    Qty in Cart: 0
    Quantity:
    Price:
    $33.55
    Subtotal:
  • COMETIC Base Gasket - Evo -  4" - .020" C9872

    COMETIC Base Gasket - Evo - 4" - .020" C9872

    COMETIC

    $33.55
    Outer layers are embossed and coated on both sides with Viton to meet the demands of a variety of harsh sealing environments, load conditions, and surface finishes, MLS (Multi-Layer Steel) head gaskets promote an even torque load across the gasket...
    09340006
    SKU:
    09340006
    Availability:
    Ships Same Business Day
    Weight:
    0.10 LBS
    MATERIAL:
    LAYERED STEEL
    THICKNESS:
    0,51 MM (0,020')
    THICKNESS METRIC:
    0.51 MM
    PRODUCT NAME:
    GASKET
    TYPE:
    CYLINDER BASE
    UNITS:
    PAIR
    BORE SIZE IMPERIAL:
    4.000'
    RIDING STYLE:
    STREET
    THICKNESS IMPERIAL:
    0,020'
    STYLE:
    STANDARD
    $33.55
    Qty in Cart: 0
    Quantity:
    Price:
    $33.55
    Subtotal:
  • COMETIC Cylinder Head/Base Gasket Pair C10167-HB-030

    COMETIC Cylinder Head/Base Gasket Pair C10167-HB-030

    COMETIC

    $81.85
    Kits feature Multi-Layer Steel (MLS) gaskets; feature two outer Viton®-coated embossed spring steel layers with an inner steel layer to provide additional support, Made in the U.S.A.
    09345927
    SKU:
    09345927
    Availability:
    Ships Same Business Day
    Weight:
    0.55 LBS
    THICKNESS:
    0,76 MM (0,030')
    THICKNESS IMPERIAL:
    0,030'
    UNITS:
    2 PACK
    MATERIAL:
    LAYERED STEEL
    MATERIAL:
    VITON
    BORE SIZE IMPERIAL:
    4.145'
    RIDING STYLE:
    STREET
    BORE SIZE:
    4,145'
    PRODUCT NAME:
    GASKET
    THICKNESS METRIC:
    0.76 MM
    TYPE:
    CYLINDER BASE
    TYPE:
    CYLINDER HEAD
    $81.85
    Qty in Cart: 0
    Quantity:
    Price:
    $81.85
    Subtotal:
  • COMETIC Tappet Cover Gasket C10172

    COMETIC Tappet Cover Gasket C10172

    COMETIC

    $23.30
    Made in the U.S.A.
    09345933
    SKU:
    09345933
    Availability:
    Ships Same Business Day
    Weight:
    0.21 LBS
    MOUNTING POSITION:
    FRONT
    MOUNTING POSITION:
    REAR
    THICKNESS METRIC:
    0.81 MM
    UNITS:
    10 PACK
    MATERIAL:
    AFM (ALUMINUM FOAM MATERIAL)
    TYPE:
    TAPPET COVER
    PRODUCT NAME:
    GASKET
    RIDING STYLE:
    STREET
    THICKNESS:
    0,81 MM (0,032')
    THICKNESS IMPERIAL:
    0,032'
    $23.30
    Qty in Cart: 0
    Quantity:
    Price:
    $23.30
    Subtotal:
  • COMETIC Cam Cover Gasket 5 Pack C10173

    COMETIC Cam Cover Gasket 5 Pack C10173

    COMETIC

    $24.80
    COMETIC Cam Cover Gasket 5 Pack
    09345934
    SKU:
    09345934
    Availability:
    Ships Same Business Day
    Weight:
    0.11 LBS
    PRODUCT NAME:
    GASKET
    THICKNESS:
    0,81 MM (0,032')
    THICKNESS IMPERIAL:
    0,032'
    MATERIAL:
    AFM (ALUMINUM FOAM MATERIAL)
    RIDING STYLE:
    STREET
    THICKNESS METRIC:
    0.81 MM
    TYPE:
    CAM COVER
    UNITS:
    5 PACK
    $24.80
    Qty in Cart: 0
    Quantity:
    Price:
    $24.80
    Subtotal:
  • COMETIC Piston Jet Gasket Pair C10174

    COMETIC Piston Jet Gasket Pair C10174

    COMETIC

    $5.95
    Made in the U.S.A.
    09345935
    SKU:
    09345935
    Availability:
    Ships Same Business Day
    Weight:
    0.11 LBS
    MATERIAL:
    AFM (ALUMINUM FOAM MATERIAL)
    PRODUCT NAME:
    GASKET
    RIDING STYLE:
    STREET
    THICKNESS:
    0,81 MM (0,032')
    THICKNESS METRIC:
    0.81 MM
    TYPE:
    PISTON JET COOLER
    UNITS:
    2 PACK
    THICKNESS IMPERIAL:
    0,032'
    $5.95
    Qty in Cart: 0
    Quantity:
    Price:
    $5.95
    Subtotal:
  • COMETIC Cylinder Base Gasket Pair C10177

    COMETIC Cylinder Base Gasket Pair C10177

    COMETIC

    $33.55
    Center or shim layer is uncoated stainless steel, which can be varied to accommodate multiple thickness requirements, Outer layers are embossed and coated on both sides with Viton to meet the demands of a variety of harsh sealing environments, load...
    09345937
    SKU:
    09345937
    Availability:
    Ships Same Business Day
    Weight:
    0.16 LBS
    MATERIAL:
    STEEL
    THICKNESS METRIC:
    0.36 MM
    MATERIAL:
    VITON
    PRODUCT NAME:
    GASKET
    RIDING STYLE:
    STREET
    THICKNESS IMPERIAL:
    0,014'
    TYPE:
    CYLINDER BASE
    UNITS:
    2 PACK
    $33.55
    Qty in Cart: 0
    Quantity:
    Price:
    $33.55
    Subtotal:
  • COMETIC Cylinder Head Gasket C10192

    COMETIC Cylinder Head Gasket C10192

    COMETIC

    $61.90
    Center or shim layer is uncoated stainless steel, which can be varied to accommodate multiple thickness requirements, Outer layers are embossed and coated on both sides with Viton to meet the demands of a variety of harsh sealing environments, load...
    09345953
    SKU:
    09345953
    Availability:
    Ships Same Business Day
    Weight:
    0.40 LBS
    THICKNESS IMPERIAL:
    0,040'
    THICKNESS METRIC:
    1.02 MM
    BORE SIZE:
    4,320'
    PRODUCT NAME:
    GASKET
    TYPE:
    CYLINDER HEAD
    RIDING STYLE:
    STREET
    UNITS:
    2 PACK
    BORE SIZE IMPERIAL:
    4.320'
    MATERIAL:
    LAYERED STEEL
    $61.90
    Qty in Cart: 0
    Quantity:
    Price:
    $61.90
    Subtotal:
  • COMETIC Cylinder Head Gasket C10193

    COMETIC Cylinder Head Gasket C10193

    COMETIC

    $61.90
    Center or shim layer is uncoated stainless steel, which can be varied to accommodate multiple thickness requirements, Outer layers are embossed and coated on both sides with Viton to meet the demands of a variety of harsh sealing environments, load...
    09345955
    SKU:
    09345955
    Availability:
    Ships Same Business Day
    Weight:
    0.35 LBS
    BORE SIZE IMPERIAL:
    4.500'
    THICKNESS IMPERIAL:
    0,040'
    THICKNESS METRIC:
    1.02 MM
    UNITS:
    2 PACK
    PRODUCT NAME:
    GASKET
    RIDING STYLE:
    STREET
    TYPE:
    CYLINDER HEAD
    BORE SIZE:
    4,500'
    MATERIAL:
    LAYERED STEEL
    $61.90
    Qty in Cart: 0
    Quantity:
    Price:
    $61.90
    Subtotal:
  • COMETIC Cylinder Head/Base Gasket C10193-HB

    COMETIC Cylinder Head/Base Gasket C10193-HB

    COMETIC

    $81.85
    Kits feature Multi-Layer Steel (MLS) gaskets; feature two outer Viton®-coated embossed spring steel layers with an inner steel layer to provide additional support, Made in the U.S.A.
    09345956
    SKU:
    09345956
    Availability:
    Ships Same Business Day
    Weight:
    0.40 LBS
    BORE SIZE IMPERIAL:
    4.500'
    THICKNESS IMPERIAL:
    0,014'
    THICKNESS IMPERIAL:
    0,040'
    THICKNESS METRIC:
    1.02 MM
    THICKNESS:
    0,36 MM (0,014')
    TYPE:
    CYLINDER HEAD
    BORE SIZE:
    4,500'
    MATERIAL:
    LAYERED STEEL
    THICKNESS METRIC:
    0.36 MM
    TYPE:
    CYLINDER BASE
    UNITS:
    KIT
    PRODUCT NAME:
    GASKET
    RIDING STYLE:
    STREET
    THICKNESS:
    1,02 MM (0,040')
    Qty in Cart: 0
    Quantity:
    Price:
    $81.85
    Subtotal:
  • COMETIC Cylinder Base Gasket Pair C10194

    COMETIC Cylinder Base Gasket Pair C10194

    COMETIC

    $33.55
    Center or shim layer is uncoated stainless steel, which can be varied to accommodate multiple thickness requirements, Outer layers are embossed and coated on both sides with Viton to meet the demands of a variety of harsh sealing environments, load...
    09345957
    SKU:
    09345957
    Availability:
    Ships Same Business Day
    Weight:
    0.16 LBS
    MATERIAL:
    STEEL
    THICKNESS IMPERIAL:
    0,014'
    UNITS:
    2 PACK
    BORE SIZE IMPERIAL:
    4.320'
    MATERIAL:
    VITON
    PRODUCT NAME:
    GASKET
    RIDING STYLE:
    STREET
    THICKNESS METRIC:
    0.36 MM
    TYPE:
    CYLINDER BASE
    $33.55
    Qty in Cart: 0
    Quantity:
    Price:
    $33.55
    Subtotal:
  • COMETIC Oil Filler Gasket C9266F

    COMETIC Oil Filler Gasket C9266F

    COMETIC

    $36.70
    Aluminum Foamette Material gaskets feature an aluminum core and a chemically blown, compounded nitrile synthetic rubber coating that is bonded to the outside layer; do not require gasket sealer., Made in the U.S.A.
    09341387
    SKU:
    09341387
    Availability:
    Ships Same Business Day
    Weight:
    0.07 LBS
    PRODUCT NAME:
    GASKET
    THICKNESS:
    0,81 MM (0,032')
    UNITS:
    10 PACK
    MATERIAL:
    AFM (ALUMINUM FOAM MATERIAL)
    RIDING STYLE:
    STREET
    THICKNESS METRIC:
    0.81 MM
    TYPE:
    TRANSMISSION
    THICKNESS IMPERIAL:
    0,032'
    TYPE:
    OIL FILLER
    $36.70
    Qty in Cart: 0
    Quantity:
    Price:
    $36.70
    Subtotal:
  • COMETIC Speed Drive Gasket C9512F

    COMETIC Speed Drive Gasket C9512F

    COMETIC

    $5.30
    Aluminum Foamette Material gaskets feature an aluminum core and a chemically blown, compounded nitrile synthetic rubber coating that is bonded to the outside layer; do not require gasket sealer. Made in the U.S.A.
    09341388
    SKU:
    09341388
    Availability:
    Ships Same Business Day
    Weight:
    0.05 LBS
    THICKNESS IMPERIAL:
    0,032'
    RIDING STYLE:
    STREET
    THICKNESS METRIC:
    0.81 MM
    TYPE:
    SPEEDOMETER DRIVE
    MATERIAL:
    AFM (ALUMINUM FOAM MATERIAL)
    PRODUCT NAME:
    GASKET
    THICKNESS:
    0,81 MM (0,032')
    UNITS:
    10 PACK
    $5.30
    Qty in Cart: 0
    Quantity:
    Price:
    $5.30
    Subtotal:
  • COMETIC Neutral Switch O-Ring C9642

    COMETIC Neutral Switch O-Ring C9642

    COMETIC

    $9.50
    High-quality products for long-term reliability, Manufactured from premium fuel-resistant materials that will not creep, crack or become brittle, Made in the U.S.A.
    09341389
    SKU:
    09341389
    Availability:
    Ships Same Business Day
    Weight:
    0.05 LBS
    APPLICATION:
    NEUTRAL GEAR SWITCH
    UNITS:
    10 PACK
    MATERIAL:
    NITRILE RUBBER
    RIDING STYLE:
    STREET
    PRODUCT NAME:
    O-RING
    Qty in Cart: 0
    Quantity:
    Price:
    $9.50
    Subtotal:
  • COMETIC Trans Top Cover Gasket C9645F

    COMETIC Trans Top Cover Gasket C9645F

    COMETIC

    $18.60
    Top end gasket kits include correct base, head gasket and cylinder O-rings as well as other top end specific O-rings or seals needed for R&R of top end, MLS head gaskets promote an even torque load across the gasket sealing surface, providing less bore...
    09341391
    SKU:
    09341391
    Availability:
    Ships Same Business Day
    Weight:
    0.30 LBS
    RIDING STYLE:
    STREET
    PRODUCT NAME:
    GASKET
    THICKNESS IMPERIAL:
    0.060'
    UNITS:
    10 PACK
    THICKNESS METRIC:
    1.52 MM
    TYPE:
    TRANSMISSION TOP COVER
    $18.60
    Qty in Cart: 0
    Quantity:
    Price:
    $18.60
    Subtotal:
  • Total: items /

Adding your products to cart

Big Power, Nice Sound!

Picked up a Pro Circuit pipe and silencer for my YZ125 it’s a game changer. The power feels way better and the sound is awesome.

Tyler D. - 06/12

Perfect Fit

First time ordering here and dang y’all knocked it outta the park! The wheels fit my Ranger UTV perfect, and I’ll definitely be back for more 5 stars all day!

Sarah L. - 08/24

Fast Shipping!!

Ordered on a Monday, and it was on my doorstep by Wednesday! Super impressed with how fast the shipping was.

Jason P. - 09/13

Helps keep cool, works great!

Bought the dual pass Allstar radiator for my build, and it’s been solid. Keeps the engine running cool even on the hottest days no complaints here!

Jake M. - 05/21

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