An 80-bhp Harris/Mark Dent RD400 Special…
Introduced in 1975 to replace the RD350, the Yamaha RD400 would quickly become the alpha wolf of the late 70s sport middleweights, producing ~40 horsepower at 7000 rpm. Front wheels soared all over the world with that two-stroke straight-twin wailing beneath them. Said Classic Bike Guide in a recent retrospective:
“The RD400 was indisputably ‘race developed’ and owners in Wrangler flares, Paddy Hopkirk Agordo lids and nylon Yamaha race jackets would run rings around the bigger, flexi-framed fours on offer at the time.”
Enter our new friend Alan Phillips of Two Stroke Heaven, a two-stroke fanatic who, at the tender age of 19, was the owner of a 450cc RD350LC (predecessor to the RZ350). Somehow, young Alan survived that bike and went on to own many more smokers to come. Among other things, Alan now owns a 465cc LC that makes a dyno-proven 103.7 bhp and an RS250/RG500 hybrid that makes nearly one horsepower for each of its 130 kilos — more on those monsters in coming features.
Today, we’re thrilled to feature Alan’s Yamaha RD400 Special, developed in conjunction with Lester Harris of Harris Performance and Mark Dent of Performance Fabrications — both of them world famous for their work in chassis development and tuning, respectively. The donor RD started as a North American Daytona that arrived in the UK by way of Greece, sporting F bodywork, YPVS wheels, and sprayed Roberts yellow…all over. Alan had a clear vision for the machine:
“With this 400 I wanted it to be the ultimate expression of that bike, while still being obviously an RD400.”
The bike is now sporting 43mm non-USD Öhlins forks, bespoke yokes, superbike-spec Brembos, and a Harris swingarm able to accommodate the BST carbon wheels. As for the engine, twin 35mm Keihins feed an engine that now puts out 80 bhp — twice that of the stock machine! Says Alan:
“I used to think I knew about two-strokes. That was until I met Mark [Dent]. He’s a genius. He made the pipes — works out all the dimensions on a computer programme — and got the fueling and ignition spot on.”
In the old days, an 80-hp middleweight two-stroke would be one vicious beast, sporting a paper-thin powerband riding the ragged edge of meltdown. However, modern tuning has worked wonders, and Alan says the RD400 has a very linear powerband and plenty of torque. A test rider from Practical Sportsbikes agreed:
“It’s weird. The motor builds revs with the urgency of a powerful stroker, yet there’s no wait for the power to chime in, it’s already there. No steps, no surprises, just relentless all the way through.”
Now we just need to buy a ticket across the Pond and beg Alan for a test ride ourselves! Below, we get the full details and specs on the build!
Yamaha RD400 Special: Owner Interview
• What’s the make, model, and year of the bike?
Yamaha RD400 Daytona registered in the UK 1987, imported from Greece.
• Why was this bike built?
I wanted to build the best three high-specification two-stroke road bikes: RD400, RD350LC, and RG500.
• What was the design concept and what influenced the build?
It was more the specifications of the bike: most BHP, best brakes, suspension, and carbon wheels. This bike still needed to look like the original from 20 feet away.
• What custom work was done to the bike?
This was a complete rebuild starting with the frame, which needed to be modified to fit the bigger swingarm to take a modern BST carbon rim. Everything on the bike is custom-made to include yokes, swingarm, pipes, rear sets, etc.
• Can you tell us what it’s like to ride this bike?
The bike has 80 bhp — it has a very linear powerband with super torque.
• Was there anything done during this build that you are particularly proud of?
Just having a 400 with carbon wheels is probably the most outstanding part, along with the air brushed paintwork from Padded Cell Race Paints.
Spec Sheet
- Carburetion: 2 x 35mm Keihin PWK, V Force 4 reed blocks, pod filters
- Ignition: Ignitech
- Chassis: Tubular steel cradle, modified/braced by Harris
- Front Suspension: 43mm Öhlins FG433, Harris yokes
- Rear Suspension: Harris box-section aluminum swingarm, Öhlins STX36 shocks
- Front Brake: 2 x 320mm floating Brembo discs, 4-pot calipers
- Rear brake: 1 x220 mm disc, 2-pot Brembo caliper
- Wheels: 5-spoke carbon BST
- Front Tire: 120/770ZR17 Pirelli Super Corsa
- Rear Tire: 150/60ZR17 Pirelli Super Corsa
- Dry Weight: 120 kilograms / 264 pounds (estimated)
- Horsepower (Rear Wheel): 78 bhp @ 9500 rpm
- Torque (Rear Wheel): 44.5 lb-ft @ 8500 rpm
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I started my facebook page Two Stroke Heaven to showcase these bikes and help other people with their builds. I have about 30,000 followers now.
Damn. An instant favorite for me. Absolutely love the classic tank shape, all the trickery, the fact that there’s usable torque, and the utterly classy right-side-up forks. In fact, I’ve never even seen non-usd Ohlins forks, where have those come from?!
Yeah, noticed that the kick start lever needs a better detent, lol, but upon closer look that was mentioned in the pic (magazine article), and the side covers should be angled more to match the tank/seat line, but otherwise this thing ticks my boxes.
Alan said those non-USD Ohlins were some of the last ever available!
Thanks. I swear, never seen ’em before, and they look absolutely fantastic. Shame that Ohlins doesn’t keep producing them. USD forks are great, but traditional forks have their place, too. Even though it’s a very different genre Honda’s XR650 standard forks are supposed to be magical for what that thing was made: the Baja desert race. I’m sure there are many street applications where a traditional fork is perfectly good.
Wow, Facebook page also has some utterly awesome sh*t.
This is an amazing build!
Beautiful build. Love the look. Love the Ohlins! The armchair race engineer in me however, wonders whether the stiff forks, mega brakes and wide sticky rubber will all combine to wind that vintage frame up and cause it to do nasty things to the handling?
Valid concern! Though they did add bracing to the stock frame, and Alan sent me an article from a UK moto journalist lucky enough to test ride the bike, who said of the experience: “Whether anyone wants to admit it or not, stock RD400s feel more like big, tuned mopeds than anything: fast, spindly, and twitchy. Alan’s does not. Long forks and shocks have lifted the bike by a good three to four inches while the quality and rigidity of the new front and rear ends have lifted the RD’s ride and handling out of the primordial swamp and nearly into the space age.”
My gut thinking is that too high spring rates and bad damping rates – either too high or too low – are what are problematic when it comes to upsetting chassis composure. Geometry is important of course, but proper suspension setup AND modern radial tires do a lot to compose a chassis. Noodly frames and swingarms/forks are usually assisted when stiffness is added to the picture. I think this is a generally true concept. But, then you have the odd cases like I mentioned above with the XR650R, where Honda found USD forks were too stiff fore/aft and didn’t work as well as traditional forks.
Who built the engine and what parts were used I am building an RD 400 and would like to boost the power
Yeah! Gorgeous! And I’m always gratified when I see an exquisite build like this using the same $30 eBay headlight brackets that I used on my budget custom build.
This is the second time I’ve read this article, and I will probably re-read a few more times before I start my project RD. It’s not the first ,but it may be my last. Finding original donor bikes is getting more and more difficult . Besides there seems to be a few four stroke twins that these “cafe kids” haven’t assaulted with their hacksaws and rattle cans. I should be able to squeeze out 2 or 3 more before my eyes or my back gives out. Great stuff, keep it up.