YAMAHA TWO-STROKE PROJECT: CODY WEBB’S E-START YZ250X

[MotoFactory]

“I’m finally doing something with my education!” says Cody Webb. He is, after all, a bona fide mechanical engineer with a Bachelor of Engineering from San Jose State University. The focus of his most recent labor is impressive. It’s a 2025 YZ250X like no other. Cody had joined Yamaha before the start of the 2025 U.S. Hard Enduro season with the express intent of crafting his own race bike using the 250X two-stroke as a starting point. Some riders wouldn’t do anything at all to the bike. It’s only been around since 2016, and it received a long list of changes two years ago. But, the platform for the bike is much older. It has a frame that was originally designed for the 2005 Yamaha YZ250 motocross bike and a motor that goes back even further. Plus, it was never intended to be a hard enduro bike. That world is dominated by European 300cc two-strokes. Some of those bikes are fuel-injected, and all have much more current electric-start motor designs. Cody’s transformation of the YZ250X into a bike that could compete at the highest level in the most demanding off-road event was a big project in a short time frame

Cody has two versions of the YZ. For the first race of the year, he ran kick-start version.

CODY THINK

Cody might not have ever worked in the engineering field, but he’s no stranger to big projects. For his senior project in 2016, he built an electric dirt bike, long before anyone ever heard of the Stark Varg. “It was probably pretty dangerous,” he admits. “But, it didn’t electrocute anyone, and I learned a lot.” After that, he set his diploma aside and worked to earn his third EnduroCross title and the 2018 FIM Superenduro World Championship. Now, he’s balancing family life with racing and trying to stay healthy.

For the Yamaha build, the first step was identifying what the bike needed and didn’t need. “I feel like the 300cc two-stroke buzz is fake news,” he said. “I specifically wanted to keep this bike a 250. Yamaha gave me the green light to do anything I wanted as long as it was still blue and kept their logos in place. I did two different race bike builds. This one has the Fisch e-start kit with a lithium battery under the seat. 

“There was a guy from Japan with an e-start Yamaha 250 two-stroke two years ago at Erzberg, and Yamaha was real secretive about it, but I did get to see the spec sheet. I know that Yamaha’s accessory division is working on one, but it might be too expensive to make it into production.

“In testing, I didn’t really have any issue with the cable clutch until I got into that last 5 percent of extreme stuff. When you’re going up nonstop creek beds and rocks, the clutch is going to heat up, and I can’t really pivot. So, on this bike, I have a Magura clutch. On the other bike, I have a Brembo hydraulic clutch. I’m pretty sure I’m the only one in North America with that. The Brembo one works phenomenally, whereas the Magura is almost too light, and that’s kind of a weird feel.” Cody combined that with a pre-production Rekluse clutch, although it’s not based on the automatic version; it’s an updated version of the manual TorqDrive.

The power delivery took some hit-and-miss testing. Cody ended up using the Boyesen Rad Valve after experimentation with almost everything available for the Yamaha. That gave him a lot more torque right off the bat, which is really what he was after. Some jetting changes were necessary. The compression was upped with the Two Stroke Performance (TSP) performance head and the medium dome. A company called Hitlis makes a reconfiguration kit for the YZ power valve that makes the power delivery more linear. Cody has the “Woods” setup as opposed to the “Desert” configuration offered by Hitlis. On the bike without the electric start, Cody uses the GYTR flywheel. The electric-start model has additional mass of its own.

The exhaust system that Cody finally settled on is the FMF Fatty: “Everyone online told me to run the Gnarly, but I felt it just numbed the power a little. The Fatty is more playful.” FMF made him a special silencer that’s about 2 inches longer than the off-the-shelf version.

Transforming the YZ250X into a hard enduro bike was something that Cody spent a long time thinking about, then a very short time actually doing. Fisch Moto sells the electric-start kit for the YZ250 two-stroke for $1090. This bike has the standard FMF silencer, but the race bike has one that’s 2 inches longer. Cody runs a two-battery system for the starter and radiator fan.

ENDURO-PROOFING

Another necessity for hard enduro is keeping the bike cool. Just upgrading the radiator cap wasn’t enough. Cody got some help from Yamaha to fabricate a mount for the electric radiator fan from a WR250F enduro bike, but had to bypass the automatic off/on switch. His bike uses a total-loss electrical system, and it will run the battery dry if the fan is on all the time. So, he has two separate batteries—one for the starter and another for the fan. He still has to manage when the fan goes on and off through a handlebar-mounted switch. Mounting that battery wasn’t difficult, but he discovered there were some unexpected issues. “I posted a photo of the battery before the King of the Motos, and there were comments that I would have to safeguard it from creating an explosion,” he said. “Apparently, it’s a BLM rule. So, I had to put it in a fire-proof bag.”

Cody is very picky about his handlebar and mounts: “I have the Renthal Twinwall 996 bars with XCGear clamps. I’ve injured both wrists now, and the mounts have some cushion to take away some harshness, which is perfect for vet riders like me.” Crash-proofing is, of course, essential. The levers are ASV unbreakable; Yamaha style on the brake side and either Brembo or Magura on the left. Bulletproof Designs makes the radiator guards and disc guard. BRP makes the chain guide, which has reinforced mounts, as well as a Bulletproof protector. The skid plate is an SxS design with the linkage protector. 

The wheels are the subject of considerable testing. An IRC JX8 Gekkota gummy tire is on a Dubya wheel with a pre-production version of a new Nuetech beadlock system in the rear. There are multiple skinny rim locks every four spokes. A foam material prevents air loss through the spoke holes, so with sealant and a half-mousse, Cody can run without a conventional tube. In front, he has a Nitromousse with a non-gummy IRC tire. The suspension was reworked by Cody’s long-time partners at Applied Technology with Race Tech Gold Valves.

Cody Webb has switched to the Yamaha YZ250X for 2025: “I think the 300 two-stroke buzz is fake news.” The Rekluse clutch is a new manual version that will be available soon.

LET’S GO RACING

Cody got the bikes from Yamaha on December 13 and had to get them race-ready by January 26 for King of the Motos. Between those two dates, he let us take the e-start version for a spin. First of all, starting a Yamaha two-stroke by pushing a button is going to make anyone smile. The electric motor spins the engine at a crazy-fast rate, so it pops to life instantly. 

As far as riding, it’s not like any Yamaha two-stroke we’ve ever ridden, but it’s certainly not like a Euro 300, either. Where the stock YZ has a slow ramp-up and a hard hit, Cody’s bike is much more linear. Compared to a 300 KTM or Beta, though, it’s much more playful. There’s just enough of a kick to be fun, even on a motocross track. But, most of the feats that Cody performs are just absurd. We have no appetite for hopping from one gigantic boulder to another or riding straight up vertical hills. Cody makes all that stuff look absurdly easy. For him, it probably is. We will take his word that the bike is amazing in those situations. It certainly looks that way. 

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