Kawasaki KX250

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The Kawasaki KX250 is a 2-stroke motocross bike that was introduced in 1974. This bike has been ridden to several AMA Motocross wins, including a number of titles, in the hands of Jeff Ward Jeff Emig and Ricky Carmichael. . The 2-stroke KX-250 was deleted from manufacture in October 2007. The Kawasaki KX250F introduced in 2004 and KX450F was introduced in 2006 and both utilize a 4-stroke DOHC engine. Many factors came into play with the demise of the 2 stroke market, however 2 strokes are once again becoming popular due to the costs associated with maintenance of the very complex workings of the 4 stroke design. Rumours abound as to when and if the Japanese manufacturers will re-introduce 2 stroke models, however this is very unlikely as the motocross sector is very small part of their business'.

1999[edit]

Liquid Cooled Engine with Kawasaki Integrated Power Valve System[edit]

  • KIPS system controls exhaust port height for increased power and torque
  • Increased flywheel effect helps the rear tire hook up
  • The output shaft now has involute splines at the countershaft sprocket for less play, quicker acceleration and increased durability

Keihin Power Jet PWK38S Carburetor with K-TRIC[edit]

  • New "shorty" design places the mainjet closer to the cylinder for improved throttle response
  • Kawasaki Throttle Responsive Ignition Control (K-TRIC) uses a sensor and alter ignition timing according to throttle position and engine speed for better throttle response and more power
  • Power jet system uses an electronic solenoid to close a fuel passageway at high rpm to extend the power peak and increase top-end power at over-rev

Airbox and boot[edit]

  • New airbox and stiffer connecting boot improve airflow around the shock to improve top-end power

UNI-TRAK Rear Suspension[edit]

  • Cast aluminum section is redesigned for less unsprung weight and more rigidity
  • Redesigned needle bearings and sleeves reduce unsprung weight and prevent incorrect assembly that can cause them to bind
  • The shock now features both low- and high-speed compression damping adjustments
  • The shock oil seal head assembly and adjuster cap changed to aluminum and the aluminum shock clevis is now lighter to reduce unsprung weight
  • New triple-rate shock spring improves suspension action at full compression

46 mm Upside Down Cartridge Fork[edit]

  • New aluminum upper fork tubes are smaller in diameter at the upper clamping area (54 mm to 52 mm) for a plusher ride and less weight
  • Stronger inner and outer fork tubes have more overlap to improve suspension action, especially on "slap-down" landings
  • New rubber bottoming damper and 10 mm longer fork bottoming cone reduce bottoming
  • New fork leg lowers with two-bolt axle clamps increase front end rigidity
  • Several internal components changed to aluminum

Front and Rear Disc Brakes[edit]

  • New ceramic coating on backing of rear brake pads insulate them from heat
  • Backing plates now thicker to prevent warping under extreme conditions

High Tensile Steel Perimeter Frame[edit]

  • Upper frame rails lowered slightly to lower fuel tank and provide flatter seating position
  • New aluminum rear sub-frame

Detail Changes[edit]

  • New graphics and restyled rear fender and radiator shrouds
  • Flatter seat allows freer rider movement
  • New handgrips offer better feel
  • Rerouted clutch cable for easier pull

by: naudia vengeace from commerce Texas

2000[edit]

Liquid Cooled Engine with Kawasaki Integrated Power Valve System[edit]

  • Revised porting for increased low-end and mid-range power
  • Revised KIPS system controls exhaust port height for increased power and torque
  • KIPS governor bearing size is larger for increased durability

Electrofusion cylinder[edit]

  • Improves heat transfer for consistent power output
  • It is porous so it holds lubrication well
  • It is hard so it resists abrasion and seizure
  • Allows closer piston-to-cylinder clearances for more power

Keihin Power Jet PWK38S Carburetor with K-TRIC[edit]

  • "Shorty" design places the mainjet and slide closer to the cylinder for improved throttle response
  • Kawasaki Throttle Responsive Ignition Control (K-TRIC) uses a sensor and alter ignition timing according to throttle position and engine speed for better throttle response and more power
  • Revised Power Jet system uses an electronic solenoid to close a fuel passageway at two separate rpm settings to extend the power peak and increase top-end power at over-rev

UNI-TRAK Rear Suspension[edit]

  • Cast aluminum section is redesigned for less unsprung weight and more rigidity
  • The shock now features both low- and high-speed compression damping adjustments
  • Aluminum shock components reduce unsprung weight
  • Triple-rate shock spring makes shock action even more progressive

46 mm Upside Down Cartridge Fork[edit]

  • New bladder system helps smooth out jolts and control bottoming
  • New .43 kg/mm fork springs
  • Polished internal surfaces for smooth action
  • New piston assembly on the cartridge is speed sensitive

Front and Rear Disc Brakes[edit]

  • Redesigned front brake caliper for better feel
  • Improved dust seals at the rear brake lever and caliper

High Tensile Steel Perimeter Frame[edit]

  • Compact and quick handling
  • Removable aluminum rear sub-frame for easy access to the rear shock

Detail Changes[edit]

  • New graphics
  • Flat seat allows free rider movement
  • New handlebar bend for increased rider comfort

2001[edit]

First gear ratio changed and flywheel weight changed for better throttle response and acceleration

2002[edit]

Higher Compression Ratio, Beefier 48mm forks,new twinspark ignition system, new 2 piece KIPS powervalve, and revalved rear shockit

2003[edit]

New Perimeter Frame, Fuel Mixes, from 30:1, to 40:1 or 52.5:1

2004[edit]

Shorter swingarm gogo

2005[edit]

Even Suspension Layout

Larger Fuel Tank

Larger Radiator

Internal Spark Arrestor

Oppositional Combustion Chamber Layout

Third Gear Ratio Moved Up 0.012 Degrees

Combustion Rate Improved

Leading Fuel Line Made 2 mm Wider for Enhanced Riding Capabilities

Angled Piston Improves Horsepower by 2HP

Riding Position Lowered for Easy Handling

King Hart Racing Chain is Stock

Wobbling at High Speeds is Reduced By Carefully Shaped Air-Intake Ports

An Extra large aftermarket Spark Plug is Stock

Spark Arrestor 1.2 mm Wider

Heat Proof Radiator Tubes Increase Performance

Entire Exhaust System polished on inside for Lower fuel consumption

Radiator Capacity has Increased From 800mls to 1030mls.

Evolved Piston head shape Increases displacement by 4cc

0.25 Litre Engine enhanced by stronger fuel Jets

8 Litre Fuel tank is increased to 8.5 Litres

2006[edit]

Renthal aluminum handlebars.
New piston profile and muffler design.
New reed valve stopper to improve low-rpm response
New water-pump impeller
Petal-shaped brake discs
New rear shock w/dual compression adjustability
Kayaba AOS (Air-Oil-Separate) fork w/one-piece TCV sleeve
New graphics and seat cover