Tech: Husaberg (KTM) 2 Stroke Top End Rebuild 250/300 TE/EXC
29th March 2016

If you love the smell of a smoker in the morning then you are only ever 120 hours away from a top end rebuild. 120 hours you say?! Well sure run times can vary from 40 hours for aggressive riding to 120+ for the more sedate of us but, sooner or later, your time will come. I find the sweet-spot for my riding is around 80-100 hours.

So should you pay to have the work done or roll up your sleeves? Join us in the workshop as we walk you through the process we used there is no warranty expressed or implied.The process itself isn’t to hard but you will need a reasonable toolkit and a smidgen of patience.


  • 13mm, 10mm, 8mm, 6mm Sockets
  • 13mm Ring Spanner (possible with open ended but not recommended)
  • Spark Plug Socket
  • Non-marking mallet
  • Small blow torch (not essential)
  • Torx Sockets (sizes tbc)
  • Flat ended screwdriver
  • Long nosed pliers
  • Spring Puller (achievable with pliers but not recommended)
  • Some workshop towel
  • A Bike Stand (possible without)

The Parts List:

  • Piston Kit (check existing piston for size)
  • Top End Gasket Set
  • ScotchBrite (medium or hard is fine)
  • Cleaning Solvent


  • Drain Coolant
  • Remove Seat
  • Remove Tank and Radiator Shrouds
  • Remove Thermostat Housing and associated hoses (for extra access remove radiators, not required)
  • Disconnect Battery Terminals
  • Remove Top Engine Mount
  • Remove Exhaust Expansion Chamber (some after market skid plates may require removal)
  • Remove Starter Motor from starter Assembly
  • Remove Spark Plug Lead
  • Remove Power Valve Control Cover (kick start side)
  • Remove Power Valve Control Arm Clip
  • Pop Off Power Valve Control Arm
  • Remove Power valve Control Cover (starter side)
  • Remove Cylinder Head (6 bolts)
  • Remove Cylinder (4 x 13mm Bolts) Use ring spanner for two forward facing bolts
  • Extract Cylinder (may require some heat and a small tap) Taking care not to allow connecting rod to drop against engine casings when removing cylinder
  • Place workshop towel around connecting rod covering crankcase opening, dropping parts in here will prove terminal!
  • Remove piston circlip, often following by search for piston circlip
  • Extract Gudgeon Pin – taking care not to stress lower con rod bearings
  • Remove Piston and Needle Bearing
  • Inspect Piston and Cylinder for abnormal wear, scratches or damage to the Nikasil coating.
  • Note Piston size and order parts

Reassembly Preparation:

  • Clean all parts remove all traces of dirt or old gaskets, taking care not to damge mating surfaces (no dremmel use!!!)
  • Prep Cylinder using ScotchBrite in a cross-hatched fashion
  • Check ring end gap adjust using a file if required
  • Lightly Oil Cylinder Bore Needle Bearing and Piston with Two Stroke Oil
  • Lubricate Cylinder Dowels with Copper Grease


  • Insert Needle Bearing
  • Insert Piston/Gudgeon Pin (check piston orientation)
  • Locate Piston Circlip
  • Install Piston rings against locating studs (rear of engine)
  • Remove Workshop Towel (there will always be one)
  • Install Cylinder Gasket
  • Install Cylinder using one hand to compress rings, taking care not to damage rings
  • Part Tighten Cylinder use cross pattern whilst tightening
  • Tighten Cylinder bolts to 30Nm, a torque wrench won’t fit so practice tension on a bolt in a vice if required.
  • Check piston movement using kick starter, look for anything unusual
  • Replace Cylinder head and gaskets use cross pattern to 18Nm
  • Replace Spark Plug and HT Lead
  • Attach Power valve Control Arm and Replace Clip
  • Replace Power Valve Covers Left and Right 10Nm
  • Replace Thermostat Housing and pipes
  • Replace Top Engine Mount
  • Replace Starter Motor/Cover
  • Replace Exhaust Expansion Chamber
  • Replace Tank and Radiator Shrouds
  • Reconnect Battery
  • Replace Seat
  • Replace coolant

Now it’s time to break the engine in, we will have a guide up soon for the process we use. In the meantime check out google for proper break in procedures before thrashing your pride and joy.

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