Complete Engine Rebuild Kit KTM 125 SX '01

The Vertex Complete Engine Rebuild Kit is a single-box solution for a full top-to-bottom rebuild of the two-stroke engine in the 2001 KTM 125 SX. Instead of chasing individual part numbers for the crank, piston, gaskets, seals and bearings, you order one kit and get the matched components needed to put the motor back together.

It suits riders, racers and workshops facing a scheduled refresh or a tired motor — the sort of job where sourcing parts one at a time costs more time and usually more money. Components come from Vertex, Hot Rods and Hot Cams, and the kit is model-specific, so the contents are matched to this application rather than a generic parts assortment.

Note: Wrench Rabbit rebuild kits are now branded as Vertex. The components are unchanged, but the box you receive may differ from the one pictured.

• Model-specific complete engine rebuild kit for the 2001 KTM 125 SX
• One order covers the crank, piston, gaskets, seals and bearings for a full rebuild
• Vertex piston kit and gaskets
• Hot Rods crankshaft and main bearing kit
• Includes water pump rebuild kit and transmission bearing kit
• Costs less than buying the same components individually
• Parts manufactured in the USA
• Formerly sold as a Wrench Rabbit kit — same components, Vertex branding

• Crankshaft
• Piston kit
• Complete engine gasket kit
• Oil seal kit
• Main bearing and seal kit
• Water pump rebuild kit
• Transmission bearing kit
• Countershaft bushing/seal kit
• Exact contents vary by application — the cam chain listed in the Vertex range applies to four-stroke kits only

Installation is a full engine strip and rebuild — have it carried out by a qualified mechanic, or work to the KTM factory workshop manual for this model.
Before you begin, unpack and check every component against your engine and the manual; confirm fitment before dismantling anything or removing parts from their packaging.
Inspect the cylinder bore, crankcases and gearbox for wear or damage while the engine is apart — a rebuild kit will not correct a scored bore or damaged cases.
Clean all mating surfaces back to bare metal and remove old gasket material before fitting the new gaskets and seals; don't reuse old seals or circlips.
Pre-lubricate the piston, rings, small end and main bearings on assembly, and fit the piston with the ring locating pins and arrow oriented as the manual specifies.
Use the manufacturer's torque figures and tightening sequences for the cases, head and cylinder base, and fit new circlips with the opening away from the piston pin cut-out.
Refill with fresh gearbox oil and coolant of the grade and quantity KTM specifies after the water pump rebuild, then check for leaks before riding.
Run the engine in gently through several heat cycles with varied throttle and full cooling between them; avoid sustained full throttle or long idling until run-in is complete.
Re-check head and cylinder base fasteners, coolant level and gearbox oil after the first run-in session.
Store any unused kit components sealed in their original packaging in a cool, dry place so bearings and seals stay clean and free of corrosion.