The Yamaha WR250X Rebuild

Lots of detail here so follow along carefully. I assume the first thing you want to know is, “What the hell is a WR250X?” One thing for sure, it is a unique bike in the truest sense. I highly doubt another one exists. It has a Yamaha 2007 YZ250 engine that uses a 2012 WR450F gear set and a newer model YZ250X airbox, exhaust pipe and other modern components situated in a 2007 YZ250 frame. The CDI box is from the 2007 YZ and at this time I’m using the 2019 YZ250X stock (black) exhaust and other bolt-on items. Let all that sink in.

In early 2014, I picked up a very lightly used 2007 YZ250 that had an Ohio title. Yes, very nice. A real title. Thus, I was able to get a plate for this bike after installing all of the requisite components to make the motorcycle legal for street use. An Acerbis DHH headlight and taillight were installed along with a clutch perch with the mount for a mirror. A license plate holder was deployed and a re-chargeable lithium battery was secured under the seat. A nice TrailTech Endurance odometer was utilized and it passed inspection without much scrutiny.

I raced this particular bike in a couple other states and it has traveled to both South Dakota and Idaho for some Western US mountain riding. It’s been around a bit. When I first got it, the late (and great) Kenny Henry split the cases and installed the WR426/450 gear set in the transmission and did the top end. Mark had already implemented this setup for Jesse and I so knew it wasn’t a big task for the crew at Lee’s. A slight bit of grinding on the cases allows one of the wider ratio gears to fit. The primary shaft from the WR drops right into place in the YZ cases.

All of the standard maintenance had been done to the bike since that time, but the top end had only been done once and the cases hadn’t been split since 2014. I told John R. in October that the old ride was coming his way for a refresh. He said to only bring the engine. Ok. A ground up rebuild ensued. The engine was pulled and delivered to John, he did the WR tranny install in my 2019 YZ250X and was familiar with the whole process. Thanks John!

He had the engine for a couple weeks. During this period, I scrubbed, polished, sanded, brushed, and/or replaced every nut, bolt, and washer. All of the aluminum components were polished and the suspension bearings and seals were replaced. Have you seen those old Dirt Rider magazines from the “phenomenal” Jimmy Lewis days where he disassembles a whole bike and lays it out on a white surface and grabs a photo? I had that scenario going on in my garage. Methodical.

During this period, I noted that one of my forks seals was leaking. And wouldn’t you know it, the damn shock seal was too. That’s the second time on that particular shock. Oh well, time for a refresh. Both of the forks and the shock were sent to Suspension Plus in Elizabethtown. The forks needed more attention than I realized, as some of the internals were severely worn. Billy did a great job and got everything back to me in a timely manner.

So in the end, I blew my budget. The whole endeavor cost half again as much as expected. I replaced and/or restored every bolt, washer, nut, gasket, sprocket, bushing, guide, seal, bearing, body plastic and filters. But, in the overall scheme of things, it was very reasonable when compared to the cost of a newer bike. Below is a detailed listing of components.

• 2007 YZ250 Frame and Subframe
• 2007 YZ250 Engine with WR-F Transmission Gear Set
• 2020 YZ250X Airbox, Rear Fender, Front Fender & Side Panels
• 2017 YZ250X Radiator Shrouds and Graphics
• 2019 YZ250X Exhaust Pipe
• 2019 YZ250X Clutch Springs
• 2012 WR450F Front Brake Hose (up and over)
• 2012 WR450F Lower Triple Clamp (tapped for chainsaw mount)
• 2007 YZ250 ProAction Valved Suspension maintained by Suspension Plus
• 2015 WR450F Headlight Assembly
• Steahly 13oz. Flywheel Weight
• Moto Tassinari VForce3 Reeds
• GYTR Clutch Cover
• ICW Gusseted Raidiators
• IMS Oversized Gas Tank
• IMS Pro Series Pegs
• Renthal CR-hi Bend Bars
• Scotts Bar Clamp & Steering Damper
• Scott Grips (full waffle)
• TrailTech Endurance II Odometer
• Flatland Racing Radiator Guards & Skid Plate
• TM Designworks Chain Guide, Slide, Roller, and Case Saver
• Pro Moto Billet Kickstand
• Guts Racing Tall Soft Seat Foam with Custom Cover (no grip on top)
• Boyesen Water Pump Impeller
• FMF Q-Stealth Silencer
• DID X-Ring Chain
• Sunstar Steel Sprockets (14-52)
• Acerbis License Plate Holder & Tail Light
• Kriega OS Loop Straps (rear fender)
• Kriega Grab Strap (forks)
• Tugger Grab Strap (seat)
• Tusk Enduro Lighting Lithium Ion Battery
• Tire Balls (front and rear)
• Moose Racing Solid Rear Rotor (DP Brakes)
• Kenda Equilibrium with TireBalls (rear)
• Michelin StarCross Soft with TireBalls (front)

Like a friend said, “You’ve got a brand new bike!” He was right, and for some reason, I like the power delivery on this engine more than my 2019 YZ250X. The 2019 (X) and the 2007 (YZ) CDI boxes are different and so is the exhaust pipe and silencer, but otherwise they are identical.

Use the gallery below to view the full resolution images of the finished product and engine closeups. It’s been a good project and nice to do when the weather isn’t great for getting outdoors. I have a few more minor updates to make but otherwise, its ready for a couple break-in rides. I’d say that most folks, other than Jesse and Travis, couldn’t tell the difference in this bike and a newer model Yamaha YZ250X. The differences are subtle.

I’ll be putting this bike to good use over the next few months. Lots of work to do where I ride and it will be the main method of porting saws and such into the woods.

See you on the trail!