Dirt Bike Engine
Dirt Bike Engine Parts at JJ Motorsports
Discover a full range of dirt bike engine components for rebuilding or upgrading your performance from JJ Motorsports. From crankshafts to cylinder heads and piston kits, these precision-engineered components ensure reliable performance. For additional upgrades, check out our full selection of off-road dirt bike parts to keep your engine running at peak efficiency on the track or trails.
Shop trusted brands like Wiseco for forged piston kits and K&N for high-flow oil filters. Explore related categories such as Dirt Bike Air and Fuel for intake upgrades or Dirt Bike Exhaust for complete systems.
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
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On Sale
PROX Valve and Spring Kit 28.SIS2424-2
PROX
MSRP: $212.95Now: $167.00Was: $212.95If you're running high-RPM conditions or boost-dependent applications, your OEM valve train wasn't designed to handle the sustained punishment. The PROX 28.SIS2424-2 replaces weak factory valves and springs with nitrided steel components engineered to...09261024- SKU:
- 09261024
- Availability:
- Ships Same Business Day
- Weight:
- 0.26 LBS
- PRODUCT NAME:
- SPRING KIT
- TYPE:
- VALVE
- MATERIAL:
- STEEL
- APPLICATION:
- INTAKE
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
MSRP: $212.95Now: $167.00Was: $212.95 -
On Sale
PROX Valve and Spring Kit 28.SIS6329-2
PROX
MSRP: $155.95Now: $127.00Was: $155.95Stock valve springs lose their tension under sustained high-RPM operation, causing valve float and compromised combustion timing—exactly when you need precision the most. The PROX 28.SIS6329-2 pairs nitrided steel valves with premium chrome vanadium...09261436- SKU:
- 09261436
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- PRODUCT NAME:
- SPRING KIT
- TYPE:
- VALVE
MSRP: $155.95Now: $127.00Was: $155.95 -
On Sale
PROX Valve and Spring Kit 28.SES4335-1
PROX
MSRP: $155.95Now: $127.00Was: $155.95If you're running your engine hard—whether on the track or in sustained high-RPM conditions—OEM valves and springs become the weak link. The PROX 28.SES4335-1 Kit replaces them with nitrided steel valves and premium chrome vanadium springs engineered to...09261457- SKU:
- 09261457
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- PRODUCT NAME:
- SPRING KIT
- MATERIAL:
- STEEL
- APPLICATION:
- EXHAUST
- TYPE:
- VALVE
MSRP: $155.95Now: $127.00Was: $155.95 -
On Sale
PROX Valve and Spring Kit 28.SIS2402-2
PROX
MSRP: $212.95Now: $167.00Was: $212.95If you're pushing your engine to its limits, OEM valves and springs will fail you—they simply aren't engineered for sustained high-RPM abuse. The PROX 28.SIS2402-2 replaces those weak points with nitrided steel valves and premium chrome vanadium springs...09261460- SKU:
- 09261460
- Availability:
- Ships Same Business Day
- Weight:
- 0.35 LBS
- PRODUCT NAME:
- SPRING KIT
- TYPE:
- VALVE
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- APPLICATION:
- INTAKE
- UNITS:
- KIT
MSRP: $212.95Now: $167.00Was: $212.95 -
On Sale
PROX Exhaust Valve 28.6520-1
PROX
MSRP: $56.95Now: $47.00Was: $56.95Exhaust valve performance directly impacts cylinder head efficiency and engine longevity. The PROX 28.6520-1 delivers OEM-specification precision without compromise, ensuring reliable valve sealing across high-cycle operating conditions. For racers and...09260688- SKU:
- 09260688
- Availability:
- Ships Same Business Day
- Weight:
- 0.11 LBS
- RIDING STYLE:
- OFF-ROAD
- APPLICATION:
- EXHAUST
- MATERIAL:
- STEEL
- PRODUCT NAME:
- VALVE
- RIDING STYLE:
- ATV
- UNITS:
- EACH
MSRP: $56.95Now: $47.00Was: $56.95 -
On Sale
PROX Valve and Spring Kit 28.SIS1403-2
PROX
MSRP: $143.95Now: $119.00Was: $143.95If you're running your engine hard—whether on the track or in high-RPM tuning applications—OEM valves and springs become your weakest link. The PROX 28.SIS1403-2 Kit replaces them with nitrided steel valves and premium chrome vanadium springs engineered...09261020- SKU:
- 09261020
- Availability:
- Ships Same Business Day
- Weight:
- 0.34 LBS
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- SPRING KIT
- UNITS:
- KIT
- TYPE:
- VALVE
MSRP: $143.95Now: $119.00Was: $143.95 -
On Sale
PROX Connecting Rod Kit 03.6011
PROX
MSRP: $116.95Now: $93.00Was: $116.95A connecting rod failure mid-race means a catastrophic engine failure—and a ruined season. The PROX Connecting Rod Kit 03.6011 delivers OEM-quality construction with precision-engineered components that transfer combustion force reliably from your...09230625- SKU:
- 09230625
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- PRODUCT NAME:
- CONNECTING ROD
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
MSRP: $116.95Now: $93.00Was: $116.95 -
On Sale
PROX Crank Bearing and Seal Kit 23.CBS61003
PROX
MSRP: $95.95Now: $76.00Was: $95.95A crankshaft rebuild demands precision-matched components that meet OEM tolerances—this is where corners cannot be cut. The PROX Crank Bearing and Seal Kit 23.CBS61003 delivers factory-spec bearings and seals in a single package, eliminating the...09240360- SKU:
- 09240360
- Availability:
- Ships Same Business Day
- Weight:
- 0.70 LBS
- PRODUCT NAME:
- BEARING AND SEAL KIT
- TYPE:
- BALL
- APPLICATION:
- CRANKSHAFT
- RIDING STYLE:
- OFF-ROAD
- STYLE:
- 2-STROKE
- UNITS:
- KIT
MSRP: $95.95Now: $76.00Was: $95.95 -
Hinson Racing Engine Plug Kit for 2009-2016 Honda CRF450R EPK489
HINSON RACING
$69.99Engine plug kits are critical wear items that directly impact seal integrity and prevent costly oil leaks in high-stress racing environments. The Hinson Racing Engine Plug Kit replaces factory plugs with precision-machined billet aluminum components that...09500539- SKU:
- 09500539
- Availability:
- Ships Same Business Day
- Weight:
- 0.15 LBS
- COLOR/FINISH:
- BLACK
- PRODUCT NAME:
- PLUG KIT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- MATERIAL:
- BILLET ALUMINUM
- TYPE:
- ENGINE
$69.99 -
Hinson Racing Oil Filler Cap for Honda CR125R 1987-2007 OC154X
HINSON RACING
$19.99Stock plastic oil filler caps fail—they crack under vibration, strip threads, and compromise your engine's seal integrity. The Hinson Racing Oil Filler Cap replaces that weak point with precision-machined T-6 aluminum, delivering the durability and clean...09500614- SKU:
- 09500614
- Availability:
- Ships Same Business Day
- Weight:
- 0.06 LBS
- RIDING STYLE:
- STREET
- PRODUCT NAME:
- CAP
- TYPE:
- OIL FILLER
- COLOR/FINISH:
- BLACK
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$19.99 -
Hinson Racing Oil Filler Cap Yamaha YZ85 2002-2022 OC213
HINSON RACING
$19.99Your YZ85's engine deserves protection from contamination and your bike deserves better than a plastic filler cap. The Hinson Racing Oil Filler Cap upgrades both durability and aesthetics with T-6 aluminum construction that withstands the demands of...09500615- SKU:
- 09500615
- Availability:
- Ships Same Business Day
- Weight:
- 0.06 LBS
- UNITS:
- EACH
- COLOR/FINISH:
- BLACK
- PRODUCT NAME:
- CAP
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- OIL FILLER
$19.99 -
Hinson Racing Clutch Cover for Honda CRF250R 2018-2026 C794-0817
HINSON RACING
$179.99Stock clutch covers on the CRF250R aren't built for sustained high-rpm riding or the thermal stress of competitive racing. The Hinson Racing Clutch Cover replaces that weakness with billet T-6 aircraft aluminum construction, delivering superior heat...09401724- SKU:
- 09401724
- Availability:
- Ships Same Business Day
- Weight:
- 0.66 LBS
- TYPE:
- CLUTCH
- COLOR/FINISH:
- BLACK
- PRODUCT NAME:
- COVER
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- MATERIAL:
- T-6 ALUMINUM
$179.99 -
REKLUSE Clutch Cover - Beta 350-430RR RMS-323
REKLUSE
$179.00If you're running a Beta 350-430RR in aggressive terrain, your clutch cover needs to withstand constant punishment from rocks, logs, and riding boots without compromising oil retention. The REKLUSE RMS-323 delivers billet aluminum durability with a...09401789- SKU:
- 09401789
- Availability:
- Ships Same Business Day
- Weight:
- 1.05 LBS
- COLOR/FINISH:
- ANODIZED
- COLOR/FINISH:
- BLACK
- MATERIAL:
- BILLET ALUMINUM
- PRODUCT NAME:
- COVER
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- STREET
- TYPE:
- CLUTCH
- UNITS:
- EACH
$179.00 -
Rekluse Clutch Cover Sherco 250 SE-R 2018-2025 RMS-324
REKLUSE
$229.00Off-road riding demands clutch protection that won't compromise durability or oil cooling. The Rekluse Clutch Cover for Sherco 250 SE-R delivers billet aluminum construction with increased capacity—giving you enhanced lubrication under aggressive terrain...09401790- SKU:
- 09401790
- Availability:
- Ships Same Business Day
- Weight:
- 0.80 LBS
- RIDING STYLE:
- STREET
- COLOR/FINISH:
- BLACK
- PRODUCT NAME:
- COVER
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- TYPE:
- CLUTCH
- COLOR/FINISH:
- ANODIZED
- MATERIAL:
- BILLET ALUMINUM
$229.00 -
Rekluse Clutch Cover Beta 350 RR 2011-2017 RMS-323
REKLUSE
$179.00The stock clutch cover on your Beta 350 RR is a vulnerability point during aggressive trail work and high-impact riding. This Rekluse billet aluminum replacement eliminates that weakness while increasing oil capacity for sustained engine cooling and...09401791- SKU:
- 09401791
- Availability:
- Ships Same Business Day
- Weight:
- 1.00 LBS
- COLOR/FINISH:
- BLACK
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- CLUTCH
- RIDING STYLE:
- STREET
- COLOR/FINISH:
- ANODIZED
- MATERIAL:
- BILLET ALUMINUM
- PRODUCT NAME:
- COVER
- UNITS:
- EACH
$179.00 -
Rekluse Clutch Cover Husaberg FE 390 2010-2012 RMS-327
REKLUSE
$189.00The stock clutch cover on your Husaberg 390 limits oil capacity and offers minimal protection against impact and wear. This Rekluse replacement delivers increased lubrication flow for sustained clutch performance while the billet aluminum construction...09401792- SKU:
- 09401792
- Availability:
- Ships Same Business Day
- Weight:
- 1.15 LBS
- COLOR/FINISH:
- ANODIZED
- COLOR/FINISH:
- BLACK
- MATERIAL:
- BILLET ALUMINUM
- PRODUCT NAME:
- COVER
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- STREET
- TYPE:
- CLUTCH
- UNITS:
- EACH
$189.00 -
Rekluse Clutch Cover Husqvarna TC85 2014-2017 RMS-331
REKLUSE
$229.00If you're running a TC85 in competitive or high-intensity riding conditions, the stock clutch cover won't cut it. The Rekluse Clutch Cover RMS-331 replaces that vulnerable plastic with precision-engineered billet aluminum that absorbs impacts from rocks,...09401794- SKU:
- 09401794
- Availability:
- Ships Same Business Day
- Weight:
- 0.65 LBS
- PRODUCT NAME:
- COVER
- UNITS:
- EACH
- COLOR/FINISH:
- ANODIZED
- MATERIAL:
- BILLET ALUMINUM
- COLOR/FINISH:
- BLACK
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- CLUTCH
$229.00 -
Rekluse Clutch Cover KTM 450 EXC 2008-2011 RMS-332
REKLUSE
$189.00If you're running a KTM 450 EXC hard in technical terrain, the stock clutch cover becomes a liability—not a feature. The Rekluse RMS-332 replaces that vulnerable component with billet aluminum engineered to absorb impacts from rocks and logs while...09401795- SKU:
- 09401795
- Availability:
- Ships Same Business Day
- Weight:
- 1.00 LBS
- RIDING STYLE:
- STREET
- TYPE:
- CLUTCH
- COLOR/FINISH:
- BLACK
- PRODUCT NAME:
- COVER
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- COLOR/FINISH:
- ANODIZED
- MATERIAL:
- BILLET ALUMINUM
$189.00 -
Rekluse Clutch Cover KTM 450 SX-F 2012-2016 RMS-334
REKLUSE
$229.00If you're running a KTM 450 SX-F, your clutch cover takes a beating—rocks, logs, and high-speed impacts are part of the game. The Rekluse RMS-334 replaces that vulnerable OEM plastic with billet aluminum that actually absorbs punishment while maintaining...09401796- SKU:
- 09401796
- Availability:
- Ships Same Business Day
- Weight:
- 0.96 LBS
- PRODUCT NAME:
- COVER
- RIDING STYLE:
- STREET
- UNITS:
- EACH
- COLOR/FINISH:
- ANODIZED
- COLOR/FINISH:
- BLACK
- MATERIAL:
- BILLET ALUMINUM
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- CLUTCH
$229.00 -
Rekluse Clutch Cover KTM 250 SX-F 2024 RMS-335
REKLUSE
$229.00The stock clutch cover on your 2024 KTM 250 SX-F is your first line of defense against impact damage and premature wear. A billet aluminum replacement with increased oil capacity keeps your clutch system cooler and more reliable during aggressive riding,...09401797- SKU:
- 09401797
- Availability:
- Ships Same Business Day
- Weight:
- 0.86 LBS
- COLOR/FINISH:
- ANODIZED
- MATERIAL:
- BILLET ALUMINUM
- COLOR/FINISH:
- BLACK
- PRODUCT NAME:
- COVER
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- TYPE:
- CLUTCH
- RIDING STYLE:
- STREET
$229.00
