Building A 2011 YZ250 Off-Road Race Bike

YZ250 Remix

Story by Trevor Hunter

Here at DBT, we like to build bikes to perform in a variety of conditions and terrains, even if that lies outside of the bike’s designated purpose. Our “YZ125X” and “TX250” fit that mold where we turned motocross bikes into capable off-road bikes with a few simple, yet necessary add-ons. In our latest project, we acquired a 2011 YZ250 from Pro off-road racer Trevor Stewart. Stewart piloted the YZ to countless race wins, a Big6 Pro 2 championship, and even an overall win at the Big6 finale at Lake Elsinore Motorsports Park a few years back. The bike is certainly capable of winning races with the right rider twisting the throttle. With its successful past, we were determined to build an off-road race bike destined for success in the 2018 AMA District 37 Big6 Grand Prix Series, albeit with a different Trevor on-board the blue machine.

The Enzo Suspension was initially setup for Trevor Stewart and worked well for our first year on the bike before a small setting change was needed.

First, the suspension was revalved by Enzo Racing who is well-known for their work with KYB settings. The settings are a little softer and more compliant from stock trim making it better suited for 1.5+ Hour grand prix races. Rolling from one garage to another, we started with Trevor’s settings in the bike, only to quickly soften up the forks and shocks as the speed difference is drastic. Still, Enzo’s Suspension was a homerun on the YZ with valving setup for T Stew transferring over with ease. With progression on the bike, we continually stiffened up the bike with clicker changes.

After a year or so of tuning and progressing with 250cc between the frame, we made a slight change to stiffen up the suspension due to the different riding styles. Stewart is a taller rider who hangs off the back of the bike more and rides silky smooth making it look effortless. I; however, ride over the front of the bike and like to hammer the rough stuff. Not an ideal style, but it’s what I’ve grown into. After the valving change, very minimal clicker changes were needed on a wide variety of terrains. From a local District 37 desert race to any given Big6 GP, the screwdriver almost never left the boot, save for a click or two on certain tracks. The suspension ran on the stiffer side and would suffer if anything ever got technical and rocky, but that was a compromise we were willing to take to get the best GP setting. The suspension soaked up all of the little chop with ease while having a progressive nature to resist bottoming through the large whoops and braking bumps.

The Bill’s Pipes combo of motor work and their exhaust system was a drastic change from stock and one we enjoyed.

The cylinder and head received some work from Bill’s Pipes and a matching pipe/silencer combo and V-Force reeds finished off the motor. The motor work done by Bill’s Pipes transformed the YZ motor into one of the best two-stroke motors we have ridden. The YZ is known for having a hard hitting, aggressive powerband leaving some looking for a different characteristic. The Bill’s work smoothened out the hit tremendously, while giving it a strong linear power all the way through the top where it seemingly never stopped pulling. The bike was easy to ride, yet very fast and fun making it the perfect combo for long off-road races. We were able to pull quite a few holeshots and top 3 starts on this bike along with 1st and 2nd overall to the bomb in the two desert races we entered the bike in.

The YZ250 had more than enough power to consistently be up front off the start.

We ran 50/50 110 race gas and 91 pump gas with Maxima 927 mixed at 32:1 at all times and never had a problem with detonation/seizing/etc. Typically, we’d replace an OEM Yamaha top end around the 25 hour mark due to the hard racing hours and trying to minimize risk of failure during a race.

We installed our tried-and-true setup of Fasst Co. Flexx Bars and a GPR Stabilizer setup for comfort in the longer races.

Next, the traditional off-road necessities include an Zip Ty IMS 3.2 Gallon Tank, GPR Stabilizer, TM Designworks Skid Plate, and Fasst Co. Flexx Handlebars. We went to our traditional GPR Stabilizer/Fasst Co. Flexx Handlebar setup as its been on our bikes for years and offers the comfort we’re looking for to minimize fatigue in the long races. AM’E Grips provide a soft contact point for our hands and eliminate unwanted blisters. ARC’s memlon levers bend and fold under impact but always return to their original shape making them an easy add-on when trying to minimize costly breaks.

Tires and tubes were supplied by Maxxis with the traditional Maxxcross SI setup being run front and rear. A TM Designworks Slide-N-Guide Kit replaced the worn out stock chain guide and slider while also adding some durability in the tough off-road conditions. Gearing wise, we dropped two teeth in the rear running a 14/48 combo at all times. This gave us a little more top-end speed while also allowing us to run each gear a little longer.

We opted to run 14/48 gearing at all times for a better top speed and to allow s to run through each gear a little longer.

With several races on the 2018 calendar, the YZ finished on the Big6 Pro 2 podium at the Hilltoppers MC 29 Palms GP while also narrowing missing out on a few other top 5 finishes. Mousse’s could have finished off those top 5’s… Additionally, the bike went on to a win and some podiums in the 250 AA class through the first five rounds of the series.

 

Overall, our 2011 Yamaha YZ250 was a great bike in the right hands. Trevor Stewart pulled off countless race wins and some championships on this bike before handing it over to someone who could never get it to go that same speed. We tried, but we couldn’t quite reach that level. Either way, the YZ performed quite well where it was designed to perform while working better than we thought it would out in the desert. While Yamaha has a purpose built off-road two-stroke available, the YZ250X, we prefer the traditional YZ as the wide-ratio 5 speed transmission isn’t appealing to our GP application. Had we set out to build a desert bike, the wide-ratio tranny may come into the conversation. Stay tuned to the site as we’ll start off with a different bike while looking for the same results…