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250 Raptor Fuel Injection Conversion


We've been working hard on Yamaha's 250 Raptor since early 2008 and can now offer the best power and reliability for Enduro or Motocross.

Along the way we've developed special parts as required,

Typical modifications include.

  • Cylinder head gas flowed.
  • Port shape, including manifold optimized.
  • Valve guide modified.
  • Oversize Inlet Valve modified then fitted
  • Valve seats recut with 3 or 4 angles.
  • Spring pressures set.
  • Head and cylinder machined for correct compression ratio and squish, this is far more effective than a heavy high comp piston.
  • Crankshaft clearances and run out checked.
  • Camshaft fitted and dialled in.
  • Piston to valve clearance checked
  • Piston modified for increase piston to valve clearance
  • Bore carburettor/match manifold and rubber
  • Lighten flywheel
Jack Pierce's 250 Raptor
Carb boring
Machined Raptor Head
  • Machine run in on Dyno if required and fuelling setup