Wiseco Complete Bottom End Kit
MSRP: $399.95
$319.96
Exact Fitment Guarantee
The Wiseco Complete Bottom End Rebuild Kit is the definitive, heavy-duty solution engineered to completely overhaul worn or failed lower engine assemblies on two-stroke and four-stroke dirt bikes. When crankshaft main bearings develop radial play or the connecting rod big-end bearing begins to fail, the entire rotating assembly must be replaced before catastrophic rod breakage destroys the crankcases and cylinder. Wiseco's complete bottom-end kit provides all premium matched components required for a complete lower-end rebuild in one package.
At the heart of the kit is a precision-forged crankshaft assembly manufactured from heat-treated alloy steel. The connecting rod is shot-peened to eliminate surface stress risers and features precision double-honed bearing journals for maximum oil flow and bearing lifespan. The kit includes Wiseco's double-sealed or open premium Koyo/NTN main bearings, a heavy-duty crankshaft counter-balance pin, hardened thrust washers, and a comprehensive bottom-end gasket and oil seal kit containing all case half gaskets, crankcase seals, water pump seals, and countershaft seals.
- Crankshaft Material: Heat-treated, double-forged alloy steel
- Connecting Rod: Shot-peened, double-honed rod with high-flow oiling slots
- Main Bearings: Precision Japanese Koyo / NTN high-RPM crankshaft bearings
- Gasket & Seal Kit: Complete crankcase, transmission, and water pump oil seals
- Factory Trueing: Assembled and trued to within OEM runout tolerances (<0.02mm)
### Step-by-Step Installation & Safety Protocols Installation requires a complete engine removal, case splitter tool, flywheel puller, and crank assembly installation tools. Remove the engine from the chassis, strip the top-end, clutch, and stator assemblies. Use a crankcase splitter tool to separate the engine cases evenly without damaging the machined gasket mating surfaces. Extract the old crankshaft and drive out worn main bearings using a blind bearing puller or heat-assisted case expansion. Press the new main bearings square into the cases. Install the Wiseco crankshaft using a crank pulling tool to draw the crank smoothly into the bearing inner race (never hammer on a crankshaft, which knocks it out of true). Reassemble cases with new gaskets, install oil seals with lips greased, and torque case bolts in sequence to OEM specs.
### Service & Maintenance Protocol Maintenance involves checking engine oil for metallic particles after initial break-in and maintaining strict oil change intervals. Ensure correct transmission fluid levels before starting.
Frequently Asked Questions
Q: Is the Wiseco crankshaft pre-assembled and trued out of the box?
A: Yes. Every Wiseco crankshaft comes fully assembled with the connecting rod, big-end bearing, and thrust washers, factory-trued to within OEM runout tolerances (typically less than 0.02mm).
Q: Can I install the crankshaft by tapping it with a mallet?
A: No. Never strike a crankshaft with a hammer or mallet. Doing so misaligns the crankshaft webs, causing severe engine vibration and rapid bearing failure. Always use a dedicated crank puller/installer tool.
Q: Does the kit include water pump and transmission seals?
A: Yes. The Wiseco bottom-end kit contains a complete bottom-end gasket and seal set, including main crank seals, countershaft seal, shifter seal, clutch actuator seal, and water pump seals.
Q: What causes connecting rod big-end bearing failure in dirt bikes?
A: Primary causes include oil starvation, running past recommended service hours, contaminated engine oil, water ingestion through the airbox, or severe over-revving.