When David O’Connor decided that he wanted to race the Vet Motocross Des Nations at the Foxhill track in England, he needed a 2002-or-older race bike. This 20-year-old renovated 2002 Yamaha YZ250 came to him as a worn-out heap.

We like to say that David O’Connor is everyone’s favorite Irishman; however, “everyone” is a relative term. We actually mean everyone in the American motocross community. Why do we like him so much? Because David has two very important qualities that guarantee success in the sport of motocross. What are we talking about? David O’Connor can talk the talk and walk the walk. No, we don’t mean “talk the talk” like a charismatic public speaker, and we don’t mean “walk the walk” like he’s a Pro-level racer. What we mean is that he’s a people person who is extremely friendly, outgoing and knowledgeable. He makes everyone he talks to feel important, and he has the mechanical skills, work ethic and riding skills to fully understand how a motorcycle works.


Anyone who wants to work in the motocross industry should take notes from David. (1) Be personable. Be honest and make friends with everyone. (2) Work hard at whatever you do. This is the formula for success in many aspects of life but especially motocross. David has worked as a mechanic for an extensive list of riders and teams, but MXA really came to appreciate him through his time spent in the press relations department at KTM. We were always thankful for his willingness to help in any circumstance, even though we still complained to him about closed-off airbox covers, not enough of a difference between maps 1 and 2, and how the spoke next to the rim lock kept coming loose. As the PR guy for KTM, it was David’s job to listen to our complaints about KTM and KTM’s complaints about us. 

Because of its long uninterrupted production run, the YZ250 two-stroke is the easiest bike to get parts for during the rebuild process. Plus, they run great. THE GEAR: Jersey: Leatt 5.5 Ultraweld, Pants: Leatt 5.5 Ultraweld, Helmet: 6D ATR-2, Goggles: Leatt Velocity 6.5 Enduro, Boots: Leatt 5.5 Flexlock.

David doesn’t work for KTM anymore because he opened his own shop, closed it and worked as a hired gun for the KTM test department, helped Dunlop with its new tire intros and started racing more. This is our second-ever test of a David O’Connor motorcycle. The first one was in 2019 when we tested David’s “Extreme 2019 KTM 250SXF build.” David’s KTM 250SXF was a showcase for KTM Factory parts. MXA’s YouTube video on that bike had 435,000 views. This test, the second one that MXA has done on one of his race bikes, came about because David signed up to race the British-held Vet Motocross Des Nations at the Foxhill track in England. Before he crated his bike to ship it to England, he had MXA run his 20-year-old Yamaha YZ250 two-stroke for him.

David’s adventure started way back in 2019 when the Vet World Cup was introduced at the Dubya World Vet Championship at Glen Helen. David convinced his Irish buddies to come represent Team Ireland for the weekend. Of course, Team Ireland had a blast and finished 14th out of the 21 international teams (of three riders each). Now, it’s David’s turn to do some serious traveling and head to England for the Vet Motocross des Nations. The major difference between these two races is that at Glen Helen, Vets are encouraged to race the latest and great motorcycles made, while at the Foxhill’s Vet MXDN, the newest bike you can run in the VMXDN class is a bike built in 2002. David’s choice of a 20-year-old YZ250 was a no-brainer, because YZ250 two-stroke parts are easy to find, largely because the bike is still in production today. 

<With the help of Millennium, Tom Morgan Racing, ProX, Wiseco piston, FMF, ICW, Cometic gaskets, Rekluse and an Andrew Langston-rebuilt crankshaft, David got the 20-year-old engine up to snuff.

David found a very rough 2002 YZ250 that had more dirt in the engine than under the fenders. His plan was to ship the bike to England, race it, and then send it on the ferry back to Ireland with his Team Ireland teammates, who would store it for him back home. A full rebuild was needed to bring this bike back to life, and master builder Jay Clark helped David gather up the parts for the build. David took the bike all the way down to the frame. He found some updated Kayaba AOSS forks and sent the suspension to Race Tech to replace the internals in the fork and shock. The engine was no simple task to refurbish. Millennium Technologies stripped the top end, repaired the damage from the previous owner and re-plated the cylinder to the stock bore. Then, Tom Morgan Racing touched up the cylinder and head. The engine was re-assembled with a long list of parts from ProX (including a connecting rod rebuild kit, main bearings, crank seals, carb rebuild kit, throttle cable, clutch cable, water-pump rebuild kit and countershaft seal kit). David also used a Wiseco piston, Cometic gaskets and a crankshaft that was rebuilt by Andrew Langston. For the clutch, David used a Cometic clutch basket and primary gear and a Rekluse inner clutch hub, and pressure plate with Rekluse TorqDrive clutch plates.


For the rest of the engine, David added FMF’s Fatty pipe and Shorty silencer, and poured in VP Racing C12 fuel mixed with Klotz R-50 premix to make it rip. David also used Uni air filters and a VForce reed cage to improve the YZ250’s breathing. ICW straightened out and braced the battered and bruised radiators. The final bits were added for Foxhill’s rocks: a carbon fiber LightSpeed skid plate, ignition cover and chain guide.

When you are rebuilding a basket case, you have to keep in mind the little things, like the axle blocks, in your planning.

When the day came for MXA to ride David’s VMXDN YZ250, we sent test riders Josh Mosiman, Dennis Stapleton and Brian Medeiros out for a few sessions to help break in the YZ250 and to speed up his testing process (as he had only left himself a few days to shake it down before crating it up). Josh and Brian have lots of experience on YZ250 two-strokes, but not one with a steel frame; however, Dennis Stapleton actually raced the 2002 Yamaha YZ250 when it was new, so he was able to offer context for our younger testers. 

Thanks to UFO Plastics, which still offers replica bodywork for the 2002 YZ250, and Clarke Racing for the white YZ250 tank in the stock shape, the bike kept its nostalgic YZ250 look. DeCal Works did a great job maintaining the vintage theme with the semi-custom red-and-white graphics kit. To make the bike look even more trick, the steel frame was sent to San Diego Powder Coating for a fresh silver paint job. Although this bike is more than old enough to vote, it didn’t feel 20 years old, thanks to ProX, who provided all of the bearings and cables needed to freshen up the YZ250. The Works Connection Elite Clutch Perch assembly and lever also offer a comfortable and modern feel at the clutch. 

David got brand-new wheels from Nacstar wheels with gold hubs and black rims. Nacstar makes a reliable wheelset at an affordable price.

Keeping in mind who the bike was designed for, Josh, Dennis and Brian evaluated the old smoker top to bottom. Starting with the engine, the YZ250 shined in the midrange, but the power window was short. It needed clutch work to get into the power, and it signed off quicker than a modern YZ250. Since this was the bike’s maiden voyage, David had to play with the jetting to dial it in. It was running lean off the bottom, so he changed the clip position and went from a 52 to a 48 pilot jet before landing in the middle on the 50. This helped smooth out the bottom end and expanded some of the power. It also helped us off the crack of the throttle.

David O’Connor’s race bike also needed some help with the suspension settings. The forks were soft in relation to the shock. In the bumps, especially under braking, the forks would compress much easier than the shock, causing the front end to dive while the rear end stepped out. The three MXA test riders are all AMA National Pros, so they had to be careful about the suspension changes they made because David is a Vet Intermediate. But, fast or slow, the soft fork/stiff shock was a no-go. Surprisingly, a 1/4-turn out on the shock’s high-speed adjuster noticeably helped the rear end stay planted, while four clicks stiffer on the non-stock Kayaba AOSS fork’s compression adjusters created enough of a balance to help our testers find the apex of the corners much easier without having to hold on for dear life. They also suggested that David tighten up the steering to help them rein in the YZ250. 

As for the chassis, David chose ODI’s 7/8-inch handlebars (instead of the more modern 1-1/8-inch oversized bars) to go with the vintage theme, and he paired them with ODI’s lock-on grips. Unfortunately, the handlebars were solid mounted with the stock YZ250 bar mounts, and that translated to a lot of vibration. On a positive note, all three MXA test riders loved the ultra-sharp Scar Racing titanium footpegs, but the 20-year-old rear brake was on the spongy side. Galfer USA provided new brake hoses, and ProX pitched in the brake pads and rotors; but, what Galfer and ProX couldn’t fix was the worn-out clevis at the rear brake pedal. It was causing a lot of extra free play in the pedal, meaning our test riders had to push the pedal down twice as far to get a normal amount of brake pressure. When you’re rebuilding a 20-year-old bike, a few parts will inevitably have their issues, and this one was minor. 

David’s Vet MXDN suspension included late-model AOSS forks and the stock Kayaba shock reworked by Race Tech.

The new wheelset was from Nacstar, a relatively new wheel company started by David’s friend Lasse Andersen, who is also a foreigner (he’s from Denmark). The Nacstar wheels were fitted with Dunlop MX33 tires, ProX chain/sprockets and Specbolt rear sprocket bolts. Specbolt also provided the rest of the bolts to simplify the rebuild process.

Once David tinkered with the jets (and we sent Dennis Stapleton out to check-ride each jetting change), we concluded that David’s YZ250 was ready for him to shake down at the last local race before the bike was sent across the pond. Every test rider agreed that the 2002 Yamaha YZ250 didn’t have the same throttle response as the 2022 model, but it was certainly impressive for a 20-year-old machine. The best part is that the new YZ250s are still rolling down the assembly line in Japan each year, so David won’t have issues maintaining this bike for a while. Good luck, David, and good luck Team Ireland at both the Vet MXDN in England the World Vet Championship World Cup at Glen Helen in November.

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