YZ / WR 315cc big bore and stroker kit Yamaha YZ250F WR250F

Motorcycles Yamaha YZF WR 300cc

Please call to order 608-842-0680

Availability: Built to order

Regular Price: $2,395

Special Price: $1,995


Product Description

For: 2001-2013 YZ / WR 250F


Cylinder: Install longer forged Aluminum sleeve, and plate with Ceramic Nickel Bore coating.  Copper fire ring installed around combustion chamber.

Crankshaft: Stroked and balanced with long rod, new pin, and lower bearing installed.

CP Piston kit

Necessary Gaskets

Base Spacer Plate

Longer Cam Chain

Longer Chain Guides

Longer head bolts

Oil line, coolant spacers, dowel extenders.

No Case Mods Required


This price is to modify your cylinder and crankshaft.  Call us if you need a cylinder and crankshaft.

Upper head mounts must be modified to clear taller cylinder, we do not provide instructions to do this.

This kit uses a 61mm stroke and a 81mm  bore (314.33cc).  The torque and mid-range gains are massive yet the build remains lively like a 250F.  Riding it is still fun and flick-able but much more hearty than a 250F big bore alone.  3rd gear is about all you need on most tracks.  Power is not like a 250 or a 450 but it is “in between”.  The best of both worlds if you ask us.

Durability is very good because of the gentle rod angles and slower piston speeds due to a bigger engine.

It is hands down the best choice for vets that like a small 250f but hate getting yarded by 450’s on the hole shot.

It was designed an tested without head work or cams and works very well that way.  However those additions will change the power delivery depending on how the head is worked over and the camshaft lift and duration.     Call us if you have questions or need ideas.  608-842-0680


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