SCITOO Cylinder Piston Top-End Kit for Honda Rancher 420 2007–2018 — 86.5mm Bore, 418cc Rebuild Kit

SCITOO Cylinder Piston Top End Kit is a complete top-end rebuild set designed to restore compression and performance on Honda Rancher 420 models from 2007–2018.

If your Rancher 420 is losing power, smoking, or showing low compression, replacing the worn top-end components can return engine responsiveness and reliability. This kit provides the main mechanical parts you need—cylinder, piston assembly, gaskets and rings—engineered to match the factory fit and restore the 418cc engine's proper cylinder dimensions with an 86.5mm bore.

Which Rancher 420 models and years will this kit fit?

This rebuild kit is made to fit a wide range of Honda Rancher 420 variants produced between 2007 and 2018. It covers AT, ES, 4x4, EPS, IRS and DCT configurations—check your specific model code and year to confirm compatibility.

• Covers TRX420FA/FE/FM/FP series including FA1, FA2, FA5, FA6, FE1, FM1, FM2 and FPA variants.
• Fits model years: 2007–2018 depending on submodel and equipment (see description for exact fitment).
• Includes compatibility for some camo editions and EPS/DCT-equipped units.

What parts are included and how do they match OEM specs?

The kit bundles the major top-end components needed for a cylinder rebuild and replaces several OEM part numbers for direct-fit installation. Components are matched to factory dimensions to help ensure correct clearances and compression once installed.

• Included: 1 cylinder, piston ring kit (piston, rings, wristpin, circlips), head gasket, base gasket, head cover gasket.
• Cylinder bore: 86.5mm; displacement: 418cc—engineered to OEM sizing for the Rancher 420.
• Replaces OEM numbers such as 12100-HP7-A00, 12100-HP5-600, 13101-HP5-600, and related top-end part numbers.

How will installing this top-end kit affect performance and maintenance?

Replacing worn top-end parts typically restores compression, reduces oil consumption and minimizes exhaust smoke when installed correctly. While not a performance upgrade, a fresh top end renews factory-level operation and can extend engine service life when paired with proper tuning and maintenance.

• Restores piston-to-cylinder clearances for reliable compression and combustion.
• New gaskets prevent leaks between cylinder head, base and cover surfaces.
• Includes wristpin and circlips to secure the piston to the connecting rod as originally assembled.

What should I check before ordering and during installation?

Verify your bike's exact model code and year against the kit's fitment list to avoid returns. During installation, inspect mating surfaces, measure clearances where necessary, and follow the factory torque and break-in procedures to ensure long-term durability.

• Compare your current cylinder and part numbers with the kit's listed OEM replacements.
• Inspect bearing, rod and crank condition—top-end rebuilds work best with a healthy bottom end.
• Follow proper assembly torque specs and perform a controlled break-in run to seat rings and gaskets.

Who is this for: This SCITOO Cylinder Piston Top End Kit is aimed at Rancher 420 owners, DIY mechanics and small repair shops needing a full top-end replacement for 2007–2018 Honda Rancher 420 models. It’s suitable for riders looking to restore factory compression and reliability after wear, seizure, or when performing a scheduled engine refresh—provided the lower end is in good condition or inspected beforehand.