336-694-3059

Dirt Rider YZ285

Call to order 608-842-0680

Price: $943

Max Power YZ285 Fits 1999-Current Yamaha YZ250 and YZ250X

Bore: 71  Stroke: 72 Displacement = 285.06cc

Engine Modifications Included:

Cylinder: Bore, Port and Plate.

Power Valves: Precision machined for optimum performance.

Head: Re-chamber to work with the Big Bore piston.  You choose the octane.

Crankshaft: No crank mods required.

Crankcase: No crankcase mods required.

Notes: This kit requires you to send us your cylinder, head, and power valves for modification.

The YZ285 is the most popular big bore kit we sell for any 250 because it works so good.  It provides a smooth predictable power delivery with just the right amount of hit to keep things fun.  You will love this kit.

When you put it on the YZ250X it completely transforms the power band,  cleans up the top end, and makes it better than that KTM300 ever was.

Check out the reviews in Dirt Rider, Motocross Action, or Dirt Bike Magazine.

Going bigger than a 71 mm bore on the stock YZ250 casting requires welding work to cylinder to keep it from popping o-rings.  The transfer ports also start to drop into that area where it becomes more of a bottom end chugger and not nearly as snappy.

Our Custom 71 mm Wiseco piston is made to be as light as possible without sacrificing durability.  It weighs only 15 grams (5%) heavier than a stock YZ250 piston.

If you already have an Athena YZ295 kit it can be livened up to close to a YZ285 style power with some porting and head adjustments.  ($300)  But I’m afraid we cant fix the vibration for you without splitting the cases and balancing the crank for you.