110-hp, 240-lb NSR-RD Hybrid…
The Honda NSR250R remains one of the most legendary bikes of the 1990s, a street-legal two-stroke weapon built in the image of Honda’s 250cc Grand Prix racers. Along with the Suzuki RGV250 and Aprilia RS250, these racer replicas were some of the last, most advanced street-going two-strokes of the 20th century.
Although emission requirements and the four-stroke revolution in MotoGP would spell the doom of such bikes, a small cult of diehard two-stroke aficionados have carried on the torch, building so-called “hybrid” restomods that combine highly modified two-stroke engines with modern brakes, suspension, electronics, tires, and more.
One such builder is Simon Cheras, a UK-born aerospace engineer who’s lived in Australia for the past decade.
“I often wondered what a modern day GP two-stroke would look like and what capabilities it would have as far as technology, geometry and aesthetics.”
While Simon could’ve gone with one of the more tried-and-true hybrid recipes, using a Cagiva Mito or Aprilia RS250 as his donor, he decided to go where no one had gone before, stuffing a highly modified RD350 engine into a 1992 Honda NSR MC21 — hence the “NSR-D Project.”
“The NSR was a legendary bike in the 90’s — having never owned one I fancied it quite a bit 🙂 Right place, right time, one came up on my Gumtree for $250 and I just went for it — it was a complete mess.”
Fifteen months later, he’d completed the “NSR-D” you see here. The RD350 engine has been bored and stroked to 421cc, boasting a laundry list of hot parts (Wiseco, Lectron, Wicked ATV, Jim Lomas, etc.).
What’s more, it has similar porting to the drag bike of world record-holder John Floyd — a tuner / racer who taught Simon much of the dark art of two-stroke tuning back in his UK days:
“I later discovered [Floyd] held the world record for the fastest two stroke (N.A. Parallel twin) and had accumulated over 35 years of two-stroke tuning knowledge. I could now write a book about John and why I consider him the number one 2t tuner in the world!!”
Other highlights include a custom chromoly cradle, CBR600 forks, Öhlins rear suspension, Brembo brakes, Tyga bodywork, carbon fenders and fuel tank, Magtek magnesium rims, quickshifter, full telemetry (GPS, lean angle, brake, and travel sensors), and more.
Weighing just 240 lbs with 110 hp on tap — and no power valve to broaden the power curve — Simons says the bike is a monster to ride:
“When it comes on song…it literally transforms into a disgusting screaming animal, completely and utterly demonic.”
Our kind of ride! And Simon says he and John Floyd are working on a 535cc YPVS (power valve) version! Below, Simon gives us the full story on this screaming NSR-D.
Honda NSR / Yamaha RD Hybrid: Builder Interview
• Please tell us a bit about yourself, your history with motorcycles, and your workshop.
Born in the UK, I worked as an engineer for an aerospace manufacturing company. Along my two-stroke riding days, some 17 years ago, I bumped into a gentleman by the name of John Floyd —
I later discovered he held the world record for the fastest two stroke (N.A Parallel twin) and had accumulated over 35 years of two-stroke tuning knowledge. I could now write a book about John and why I consider him the number one 2t tuner in the world!!
Having little money back then, John taught me what can be done with a cheap $5 set of needle files and some sandpaper. After blueprinting several other two-strokes, I had got the bug! I one day set out to build the ultimate RD +400cc Hybrid.
After moving to Australia about 10 years ago, I left most of my two-strokes behind and along with it my passion for them. But I always had this project in the back of my mind.
• Why was this bike built?
I had planned for this engine/mod to be done to my Aprilia RS250 Rossi Replica; however, as the years went by, they became that little bit rare, and so I couldn’t bring myself to chop up the frame and ruin its originality.
I often wondered what a modern day GP two-stroke would look like and what capabilities it would have as far as technology, geometry, and aesthetics.
Planning this bike was the biggest challenge. I meticulously documented and researched every part prior to the build, set out in stages of purchasing order, fabrication work, and working out what would be the quickest most efficient way to bring it all together.
I have a complete wiring diagram, dimensional sizes, cost and source of all the components used — I also keep full specs on the bike as if you brought it from a showroom!
Along with that I also made a complete workshop manual of the detailed stages of the build. (Photos attached to give you an idea.)
The next part of the project will be to make a naked version of it. Yes it looks amazing as is, but at the end of the day, the bodykit is an over-the-shelf upgrade…the true engineering lies under the fairing.
• What was the design concept and what influenced the build?
This particular hybrid build, mod, transplant had never been done before — I didn’t want to follow suit and do yet another Cagiva Mito hybrid, or an Aprilia 250 hybrid.
The NSR was a legendary bike in the 90’s, having never owned one I fancied it quite a bit 🙂 Right place, right time, one came up on my Gumtree for $250 and I just went for it — it was a complete mess.
To be completely honest, prior to doing a project or even looking at what bike/frame to use, I always see what’s available on the aftermarket. On this build I was led by Tyga’s awesome kit for the NSR and just was adamant that I would make it all fit.
I had always planned for it to be a high-tech bike, but at the same time keeping everything very simple and very very neat, easy to work on, and let’s not forget….troubleshoot 🙂
The hardest part of the build was the wiring, from start to finish I had planned it and it was the only thing that didn’t go entirely to plan and the subject I have a few regrets on 🙂
• Can you tell us what it’s like to ride?
The handling is just incredible — compared to the RS250, far superior, and THAT is an amazing handling bike.
There are no power valves with these cylinders, so the power naturally comes on similar to a light switch 🙂 which is actually what I wanted. Sure p.v’s would be nice — John Floyd and I are currently working on a PV 535cc upgrade which should be amazing 🙂
Riding the power is very fun, it will pull like a train all the way up to 11,500 rpm and with the quickshifter, you’re back straight in the power in every shift, seamless and flawless.
It’s exceptionally light at just 109kg — weight saving was high up on the list from the get go.
Yes of course it’s fast, but sitting in traffic or casually riding is also quite fun on the bike. When it comes on song…it literally transforms into a disgusting screaming animal, completely and utterly demonic. The silencers from Akrapovic were definitely worth the wait and the price tag, paired with John’s handiwork, I never had any doubt it would be anything less.
• Was there anything done during this build that you are particularly proud of?
Certainly a few things I was proud of, mainly the people I met during the build and taken back by certain people’s willingness to help you at the drop of a hat, give you their undivided attention and share the same passion for my build.
I was taught by my dear friend and engineer Mike, how to 3D print parts and prototypes, to see what shapes, angles will work for say the cradle — this was all 3D printed before it went to the laser cutters, incredible time and money saved.
I also migrated my technical (handwritten) drawing skills to Fusion 360 — 90% of the bike’s parts were drawn in CAD and designing or modifying parts to suit is just so easy once you’ve drawn it up.
It’s an amazing feeling to have 10 people literally queued up waiting to ask you about the build and “what is this thing?” The more you look at the bike, the more you discover, and sitting back and watching people converse about the bike is always a proud moment.
MC21 frame, 1992
Yamaha RD350 engine
Bored and stroked (4mm) to 421cc (110hp)
Tuned by world record holder John Floyd
Wet weight: 109kg (240 lbs)
Cheetah Cub cylinders
+4 mm hot rods crank
V force 4 reeds
Hinson complete billet clutch
Wicked ATV billet intake manifold
Pro Design cool head
Straight cut primaries
Custom one-off Akrapovic silencers by Suter
Jim Lomas expansion chambers
Chassis / Braking:
Custom-made chromoly cradle
Brembo M4 calipers
Brembo master cylinders
Öhlins rear suspension
Öhlins steering damper
CBR600 front end
Tyga body work
Tyga carbon fiber fuel tank
Tyga triple clamps
Tyga carbon fiber licence plate holder
Tyga carbon fiber F+R mudguards
Magtek magnesium rims
Rizoma stealth mirrors (3D-rubber printed mounts)
Pingel hi flow fuel outlet
Domino quick action throttle
3D printed indicators
Titanium fasteners throughout
Ultrasonic fuel level sensor
Cerakoted engine, frame, rims, and all peripherals.
Fuseless PDM by hardwire electronics
Ignitech Programmable ECU
Individual Dynatek coils
Bi directional Quickshifter (autoblip)
Vape Powerdynamo stator
Davinci Starlane GPS dash
Custom made Tefzel wiring harness
Ducati wire connectors
Ducati switching gear
Programmable fan controller
Full telemetry (GPS, lean angle, brake, and travel sensors)
Project took me 1 year and 3 months
I started with a NSD250 frame and swingarm for $250
The final cost was $38,000 AUD
All work was done by myself with the occasional help from friends