2005 Yamaha YZ Models

Below you’ll find the broad stroke specs, but for more details, check out Yamaha’s web site.






Big changes for the YZ85 are, uh, well…it gets Bold New Graphics.

Shared Features

Several features are shared on all the full-size models, including:

  • YZ bend Renthal 790 aluminum bars.
  • Improved front brake cable routing.
  • The weight of the rear swingarm has been reduced by a claimed 1.1 pounds by increasing the arm diameter from 37mm to 42mm. With stronger extruded and hydro formed arms, the weight of the cast aluminum center section has been reduced.
  • The rear brake bracket has been redesigned for weight reduction and for easier wheel installation.
  • All the full-size models also receive a fork with a new design that separates the oil and air, and features a chrome surface with Kashima Coat on the lower legs for reduced friction.
  • A full rebound oil lock system provides more controlled damping at beginning stroke of rear suspension, and prevents top-out.
  • You’ll also find a variety of smaller items, everything from making fasteners similar (and reducing the number of Allen and Phillips head bolts), an improved plastic material (to substantially minimize the milky white flex marks), to reshaping the sprockets to improve chain life.






Goals for the ’05 250F included trying to improve the feel of pulling power in low-to-mid range, as well as to improve the overall handling and comfort.

The engine received a new head with a redesigned combustion chamber, as well as a redesigned intake port, a new designed air cleaner boot, and tweaks to the carb and CDI mapping.



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For ’05, the goals were to smooth the power delivery of the big-bore thumper, as well as improve comfort and handling.

Like the 250F, the 450 got a new cylinder head with a redesigned combustion chamber, as well as a redesigned intake port and new air cleaner boot. It also gets a new clutch assembly, improved carb settings, and a modified shifting mechanism.

Aluminum Frame

The new design aluminum frame used on the YZ125 and YZ250 features a mix of cast, forged, and extruded components welded together in an attempt to retain character of steel frame with advantages of light weight aluminum. Weight is said to be four pounds lighter than last year’s steel frame.

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YZ 125

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The YZ125 gets a slew of changes, including a new compact design engine with a six-speed transmission that’s said to be four pounds lighter. The cylinder angle is 7.5 degrees forward to straighten the intake port and carburetor joint, as well as the exhaust’s head pipe.

Claimed weight for the entire bike (using the AMA method) is 196 pounds.


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The YZ250 also gets the aluminum frame treatment. In the engine department, it gets a new piston design, as well as a new pipe.

It also receives the features common to all the full-size bikes, and claimed weight is 217 pounds using the AMA Method.