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Start ShoppingProX 42.2321 Crank Seal Kit - Durable Oil Seal for 2-Stroke Engines
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Description
Keep your 2-stroke engine running smoothly with ProX's premium crank seal kit. This essential maintenance component prevents oil leaks and ensures reliable performance, even with today's high-performance fuels and premix oils.
Key Features
- OE-Style Lip Seal Design: Precision-engineered to match original equipment specifications for a perfect fit and optimal sealing.
- Spring-Loaded Sealing Lip: Maintains consistent contact with the crankshaft, reducing leakage risks and extending seal life.
- Advanced Material Construction: NBR or Viton-style rubber with metal reinforcement offers exceptional resistance to heat, oil, and modern fuel additives.
- 2-Stroke Engine Compatibility: Specifically designed for bottom-end applications, ensuring reliable performance in high-RPM environments.
Why Choose This Product
Upgrade your engine's reliability with a seal kit built for today's demanding conditions. The reinforced construction handles extreme temperatures and corrosive fuel blends, while the easy-installation design saves time during maintenance. Whether you're racing or riding recreationally, ProX's 42.2321 kit delivers long-term protection against oil leaks and premature wear.
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Keep your 2-stroke engine running smoothly with ProX's premium crank seal kit. This essential maintenance component prevents oil leaks and ensures reliable performance, even with today's high-performance fuels and premix oils.
Key Features
- OE-Style Lip Seal Design: Precision-engineered to match original equipment specifications for a perfect fit and optimal sealing.
- Spring-Loaded Sealing Lip: Maintains consistent contact with the crankshaft, reducing leakage risks and extending seal life.
- Advanced Material Construction: NBR or Viton-style rubber with metal reinforcement offers exceptional resistance to heat, oil, and modern fuel additives.
- 2-Stroke Engine Compatibility: Specifically designed for bottom-end applications, ensuring reliable performance in high-RPM environments.
Why Choose This Product
Upgrade your engine's reliability with a seal kit built for today's demanding conditions. The reinforced construction handles extreme temperatures and corrosive fuel blends, while the easy-installation design saves time during maintenance. Whether you're racing or riding recreationally, ProX's 42.2321 kit delivers long-term protection against oil leaks and premature wear.
| SKU | GM4B5CAF5A |
|---|---|
| MPN | 42.2321 |
| Brand | ProX |
| Category | Engine |
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Frequently Asked Questions
On some 2-stroke engines, one or both crank seals can be carefully removed and installed from the outside. On many others, the crankshaft must be removed and the cases split to replace the seals correctly. The required procedure is engine-specific; always follow the OEM service manual. If the crank bearings are worn, a full tear-down is strongly recommended.
It is strongly recommended, especially on used or high-hour engines. Worn crank bearings can cause excessive crankshaft movement, which quickly wears or dislodges new seals and can lead to serious engine damage.
ProX crank seal kits are designed as OEM-equivalent replacements and are widely used in race and recreational engines. Performance and lifespan are generally comparable to stock when installed correctly and used within normal operating conditions, but exact material and spec comparison depends on the specific OEM part number.
Yes. On 2-strokes, leaking crank seals allow air to enter or premix to escape, creating an unmetered air leak. This can cause lean running, hanging idle, hard starting, poor lubrication, and in severe cases piston seizure or engine failure.
Most crank seals install dry into a clean bore, but some manufacturers specify a light coat of non-hardening sealant on the outer diameter. Do not apply sealant to the sealing lip. Follow the OEM service manual instructions for your specific engine.
Installation Guide
Difficulty
Medium
Est. Time
1 hr 0 min
Tools Required
- basic metric socket and wrench set
- torque wrench
- screwdrivers and picks
- rubber or plastic mallet
- seal driver or appropriate size socket to drive seal in evenly
- flywheel puller (for ignition side on many engines)
- clutch holding tool (for primary side on some engines)
- engine stand or clean bench surface
- solvent and clean rags
Pro Tips
- Lightly lubricate the seal lip and crankshaft journal with clean 2-stroke oil before installation
- Use a thin plastic sleeve or tape over sharp keyways when sliding the seal over the crank
- Always refer to the OEM service manual for orientation diagrams and installation depth
- Check crankshaft radial and axial play and bearings while you are in the bottom end; bad bearings will quickly ruin new seals
- After assembly, pressure/vacuum test the crankcase on 2-strokes to confirm there are no air leaks
Common Mistakes to Avoid
- Damaging the new seal lip during installation by dragging it over sharp crankshaft keyways or grooves
- Installing seal backwards (spring and sealing lip must face the oil/pressure side as per service manual)
- Not cleaning or lightly polishing the crank seal journal, causing early leakage
- Driving the seal in unevenly or too deep, blocking oil passages or misaligning with the crankshaft
- Reusing hardened or damaged crankcase gaskets when cases are split
Comparison vs Stock/OEM
ProX crank seal kits are generally built to OEM-style specifications and intended as direct replacements for stock seals.
Improvements
- Often competitively priced versus OEM
- Wide availability and easy sourcing for older models
- Materials typically compatible with modern fuels and oils
Considerations
- Exact rubber compound and tolerances may differ slightly from OEM
- Always cross-reference ProX part 42.2321 with the OEM part number and application list to confirm fitment
Durability & Warranty
Expected Lifespan
Highly dependent on engine condition, maintenance, and use; on a healthy 2-stroke used recreationally, crank seals often last several seasons or hundreds of hours before needing replacement.
Warranty
Typical aftermarket parts warranty is limited and covers manufacturing defects only; verify exact ProX warranty terms on the package or manufacturer site.
Maintenance
No direct maintenance for the seals themselves; maintain correct oil, jetting, and air filtration, and periodically check for symptoms of air leaks (lean running, erratic idle, unexplained spooge changes).
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