Building a Working Replica of the Yamaha YZM400F

Jan. 08, 2015 By Rick Sieman with Rob Phillips

The man who built this phenomenal bike was Rob Phillips. He owns a small company called Husqvarna Restorations. Rob has done a large number of very famous bikes throughout the years, including bikes owned by Steve McQueen and other famous folks. For more information, contact him below.
Phone: Ask for Rob at 845-889-4499
Location: New York 
Email: [email protected]


Doug Henry on the YZM400F.

The YZM 400 is the real deal: a 1997 Yamaha works engine. It's the engine that changed history, and you could say the engine that killed the two-stroke. The engine is single-cylinder, four-speed, 5 valve, with piston and stroke very similar to Formula 1 engines. It also has unique  dual port exhaust that only exists on the these works engines. The engine case, and most all other parts of this engine, are billet aluminum and billet titanium. Fasteners are all titanium. The engine is rated at 60 hp, 13,000 rpm rev limit, and due to all the billet titanium, it weighs in 7 lbs. less than a production engine. The one unique feature of this engine as opposed to Doug Henry's, is it’s electric start with no kicker. It was built in 1997 for 1999 World Champion Andrea Bartolini. No history as to where this engine was run.

Andrea Bartolini and his Works YZM400F.

The YZM400F 1997 MX works engine was the “First Generation Prototype” OW-H2 works engine with electric start, raced by Andrea Bartolini. This is one of the YZM400 Works Engines which began the four-stroke motocross revolution and changed motocross history forever. One of the most historical motorcycle works engines of all time.

The four-stroke transition was literally started  by Doug Henry when he won the 1997 Las Vegas Supercross. It was the first four-stroke win. Doug was instrumental in the early development of the YZM400. I am honored to have him on-board. One of Doug’s many claims to fame is being the first racer of the new production YZ400F. While Doug was running his YZM400 in the USA, Bartolini and Stephen Johansson where running the same works bike in Europe.

There is no works bike before or since that changed the history of motocross like Doug Henry’s 1997 YZM400, the only “true” works bike in the AMA since the inception of the production rule. The production rule was put into effect in ‘86 to protect privateers from having to battle $100,000 engineering marvels, but Yamaha somehow worked out an exemption and worked within the highly lopsided double-displacement rule with the AMA to further four-stroke development. I’m not going to turn this into a two-stroke vs. four-stroke debate, but this bike was a 100% prototype machine and went against every production rule in the book. Because of these freedoms, Doug Henry’s YZM400 was the trickest handmade machine to ever shred a motocross or Supercross track.

Here you have the YZM400 Electric starter.

Having said that, the plan was to utilize this engine to something it deserves, instead of sitting on a shelf as a trophy. The project here was to use a production 1998 YZ400F motorcycle for this beautiful YZM400 works engine. I planned to simulate as many components as possible, as found on Andrea Bartolini or Doug Henry’s bike. My way of salvaging some very historical technology.

Doug Henry’s YZM400F. It’s the same engine minus the electric starter.

To the best of my knowledge, this is only prototype works engine with electric start known to exist. This is the engine  that revolutionized motocross world in 1997 by Andrea Bartolini  in European world motocross championship and Pete Johansson and by USA champion, Doug Henry. The two other non-electric start engines are in the only two existing motorcycles that I am aware of. One is Doug Henry’s bike, currently at Motorcycle Hall of Fame, and other is the bike in the Yamaha museum.

We did a quick fit of YZM400 motor in the donor bike.

Because the carburetor interfered with the left rear down tube on the production frame, it had to be modified.

As you will see, it is an amazing engine design by Masakazu Shiohara. The main case is CNC machined out of one block of aluminum. The brown side covers, believe it or not, are billet machined titanium. All the bolts are titanium. The 396.9cc engine is supposed to be rated at about 60 HP and redline up in the area of 12,000 RPM. The engine is also a wet-sump with only .7 quart capacity, not like the production bike that is dry sump and uses the frame as the oil  reservoir. The water pump runs off the cam, not like the production engine using the crankshaft.

Look familiar? I made an actual size copy of the Doug Henry frame down tube as a template.   Bob Morano, being a master fabricator, nailed it. You can put the photo template in front of the frame, take it away, and you will not see a difference. Things were fitted up first and then the final welding. Here you see the frame was notched for a dual output exhaust. The factory YZM frame was built with a front wishbone  portion of frame to allow for exhaust output.

Another unique feature on the YZM is the exhaust; it’s dual port and merged into one, where the production bike is single port. Piston is 95mm x 56mm stroke, but the production engine is smaller 92mm, with a longer 60.1mm stroke. The YZM has four gears, but the production bike has five gears.

Yet another overlooked detail: the sprocket cover is billet titanium.

All the plastic on this bike is NOS. I had to go from USA to Australia to Europe to get it all.

On Sept 2012, I purchased a 1998 production bike and pulled the engine from the donor bike. Weight comparison – the YZM weighted in at 54 pounds and production engine came in at heavy 61 pounds. I  worked with of Outlaw Chassis, Salt Point, New York,  on modifying the frame and fabricating the custom exhaust. The engine was a  twin exhaust port, so the exhaust had to be made custom. Production bikes are single port. As for the frame, the front down tube was notched for dual exhaust and the left rear down tube had be modified due to the fact that the intake and carburetor are at different angles and interfere with the down tube. Hence, the reason for the well recognized curved left rear down tube you see on Bartolini and Henry’s bike.  As you will see in the following  photos,  we had to duplicate that down tube to fit this engine.

The original YZM400F used larger radiators. I installed a set of Fluidyne custom radiators.

Doug Dubach Racing carbon-fiber muffler, custom made to match the Henry/Bartolini bikes. A carbon-fiber air box was added.

Once we fitted the engine to the donor, it was clear what had to be done. This is when the magic happened.  Master fabricator Bob Morano, of Outlaw Chassis, duplicated the tube almost exact, to the YZM works frame. We overlaid the life size photo on this curved frame member, that is a very recognizable part of the YZM works frame and were able to see that Bob pretty much nailed it. From there, Bob moved to the dual port exhaust and did his magic there. To finish off the exhaust, I contacted Doug Dubach, of DRD Racing, who was instrumental in the development of the YZM. Doug happened to have created in late 90's a couple silencers with the same carbon fiber used on the original YZM. Doug happened to have one left and thought it was appropriate that he donate the silencer to this project.

They spared no expense with this engine. This is the smaller “Billet Titanium” side cover and below it titanium clutch cover. Ka-ching

The carburetor air boot had to be shortened. Modified vs. Stock on right.

Since the ignition was missing, I had to come up with an alternative. The engine still had the works flywheel and magneto, so I ended up using a programmable ignition out of Germany. It's has the ability of 12 points and two different curves for ignition. I added a switch to the handlebars to select another ignition curve on the fly. I ended up using a simple ignition curve, because the last thing I need is to blow this engine up, otherwise it would be a custom made part. The bike fired up without a problem.  I had to recreate a relay starter circuit and battery for the electric starter.  The engine has very high compression, so you have to use the compression release while you crank the engine. I have since increased the cranking amps of the battery to help with this situation.

Myself and Bob rode the bike once. It's amazing.

Completed fabricating the battery box which also holds starter relay.

Assemblies ready. Paint was applied and the entire bike put together.

• 1998 YZ400F donor bike. Frame, swingarm, seat pan, forks, lower triple tree, hubs and calipers are about all that remains from the stocker.

• Titanium factory rear subframe. Titanium foot pegs and 90% of fasteners are titanium. 100% of engine fasteners are titanium.  Many components on the engine are billet titanium.

• Carbon Fiber custom engine mounts with titanium bolts.

• Carbon Fiber air  box with customized air boot. Carbon Fiber chain guide.

• Plastic is all NOS 1998 European white with custom made decals.

• Since the original ignition system is unknown, I used a new programmable DC-CDI ignition system by Zeeltronic and utilizing the original prototype stator and flywheel.

• Carburetor is a production Keihin CR, but with some modifications. I used the throttle position sensor, since the programmable CDI used one. To the best of my knowledge, the YZM did not use throttle position sensor.

• Seat was custom upholstered by Pirate Upholstery, Kingston, NY.  I used them for my Supermoto. Their work is superior. They do the seats for Orange County Choppers.

The bike was fully completed on 12/7/2013.

• Dubach Racing Development

• Advanced Racing Technologies

• Vintage Viking

• Outlaw Chassis, Salt Point NY

• Paint by Auto body Master – Mike Carter, Oklahoma City.

• Thanks to Doug Dubach for fantastic custom made carbon fiber muffler. Doug used the same carbon fiber used to build Doug Henry and Bartolini muffler. See photo below.

• YZ400F donor motorcycle. Custom decals and graphics by Senge Graphics out of Pittsburgh.  Steve has done a great job. Senge Graphics.

• I have been working on the ignition system with Kyle Wood of ElectroSport.  His help has been invaluable. Check out their website: Electrosport

• Radiators were modified Fluidyne aluminum and oversized. This was needed for this engine, since the engine is wet sump with less than quart of oil.

• New Excel rims and Excel stainless spokes and nipples. New Pirelli MX tires.

• New Front and rear brake disks with titanium bolts. New Afam rear sprocket with titanium bolts.

• New Billet GYTR compression release lever.

• New Grips with New Cables, customized.

• New Pro Taper fat handle bars. Same ones used by Doug Henry; billet aluminum top triple tree with fat bar clamps.

• New Fuel Tank.

• Authentic chain used by YZM, REGINA 135RX3-113L.

• Aftermarket kick stand.

• Unless noted, all other components are restored YZ400F. Newsletter
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