Profile shot of an raw RD 400 motorcycle in process on a bikelift. RSD logo and Build Update writing on the left

YAMAHA RD 400 TIME MACHINE

We all love two strokes around the shop. There’s something about the simplicity, the light weight, the sound, and the smell that continues to captivate us. Growing up around two strokes, rebuilding the motors, and premixing gas is something that sticks with you. When you hear one, when you smell the premix burning at 32 to 1, it transports you back to a simpler time—a time before cellphones and the modern world swallowed up the kids. It takes you back to a day when having a ratio rite, a five-gallon jug of gas, and enough oil to get you through the day was all that mattered. So here we are, going back in time with an RD 400 build, and it feels damn good.

This bike has been in our friend’s family for years and belonged to his brother. His brother passed away, and while we miss our family when they leave us, sometimes they leave a special piece of themselves behind. The RD before you is a vessel for those many good times, and it’s our job to do this machine justice. When we got the bike, it had been well-used and was at the end of its current life cycle. Apart from a worn yet assembled motor, the rest of the bike was in bins. We set about a redesign at our customer's request that kept the original form, chassis, and cases from the original machine, separating the usable parts from the swap meet items.

 

The motor had seen better days and needed a 100% restore, so we sent it out to our friend Ed Toomey, who’s been working his magic on air-cooled two strokes for as long as we can remember. Ed rebuilt the motor from the ground up with a completely new crank, rods, and top end, increasing compression with a Stage 2 porting and heads. He also added a modern ignition, reed cage assembly, Keihin 28mm carbs, and a set of still not delivered Ed Toomey pipes originally designed by legendary two-stroke tuner Erv Kanemoto. Ed also powder-coated the motor and added some fancy gold-plated bolts and back cut the transmission gears, along with adding a new clutch and sight glass into the stock side cover.

 

We were originally going to go crazy with bodywork, but after further thought, we decided to keep the original tank and eliminate the upper fairing design and tank modifications, keeping the stock aesthetic intact with a TZ 750 tail section. Instead of the fairing, we used an Indian FTR headlight and a massaged mount. This allowed us to focus on the performance aspects of the bike.

 

The wheels are from our partner Dymag: a 17 x 3.5 front with an ultra-sticky and track-friendly 17 x 120 Dunlop Q5, and the rear is a 17 x 4.5 with a 17 x 150 Dunlop Q5. The suspension was a big focus, and we went with a resprung Yamaha R6 front fork and bottom triple with a vintage RSD top triple clamp. R6 rotors and brakes with clip-ons and a Brembo master cylinder matched to the twin radial mount R6 calipers complete the stopping duties. Using an R6 fork was great because it was the right length fork—maybe a bit overkill on brakes for the weight of the bike, but we’d rather have too much stopping power than not enough. The rear of the bike got a Trac Dynamics swingarm, and we are still waiting for shocks, which we will extend to 13.5”. The rear brake bracket was made special for the bike and the single Brembo rear caliper.

 

We found some decent fitting rear sets, modified for the RD application, and fabricated a master cylinder mount directly to the frame. With the raised-up rear tail section and soon-to-be seat, the end result is a comfortable yet aggressive seating position that isn’t painful. We still have to finalize the details, finish modifications to the frame, clean everything up, and then she’ll go off to paint and finish. 

 

a photoshop render of a yamaha rd400. It has a sleek design showcasing the two stroke motor, long tank, sporty tail section and dunlop tires

It’s these types of projects that we really appreciate. It’s meaningful to bring a machine back to life that’s capable of making new memories as well as resurrecting the old. It’s as close to a time machine as we can get.

Profile shot of an unassembled RD 400 motorcycle in process on a bikelift