The real OW – YZM400 FOR SALE

1997/98 Blended Yamaha with OW – YZM400 Works engine.

Check out the article in Moto Magazine UK. May,2015  issue 115.

This is the “First Generation Prototype”

OW-H2 Works Engine with electric start,

raced by Andrea Bartolini

This is one of the OW – 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 Holy Grail

Same Works engine like one used by Doug Henry to win

1997 Las Vegas Super Cross. First four stroke win.

This is the only known existing electric start OW – YZM400 works engine

Here is Bartolini on the #72 OW – YZM400

winning Castiglione, Italy 1997  Castiglione, Italy

Compliments from my friend Trond from Norway

Nice article by Rick Sieman on Off-Road.comOff-Road

Dubach Racing Development DRD Dubach Racing

Advanced Racing Technologies

Vintage Viking Vintage Viking

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.

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.

I extracted this article from Put best by Dan Lamb about how historically significant this engine is and how rare it is for years to come. There never will a be anything like it ever again.

<<<<There is no works bike before or since that changed the history of motocross like Doug Henry’s 1997 YZM 400, 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 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 YZM 400 was the trickest handmade machine to ever shred a motocross or supercross track. >>>>>

Having said that, the plan is to utilize this engine to something it deserves, instead of sitting on a shelf as a trophy. The project here is to use a  production 1998 YZ400F motorcycle for this beautiful YZM400 works engine. I plan 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.

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 three other non electric start engines are in the only two existing motorcycles that I am aware of. One owned by Doug Henry’s bike,  one owned by Bartolin’and other is the bike in Yamaha museum.

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

If you would like to read about the YZM400 motorcycle in old magazines, here is small list of ones I have gathered. There may be more.

Dirt Bike Feb 1997 – Motocross Action June and December 1997 – Dirt Bike December 1997 – American Motorcyclist June 1997

In the Dirt Bike issue December 1997 you will see large photo of this engine.

Here is a good article on the history of YZM400 evolution on

Now on to the project……….

Sept 2012 – Purchased 1998 YZ400F donor motorcycle.

Custom decals and graphics by Senge Graphics out of Pittsburgh.  Steve has done a great job. Check him out.Senge Graphics

Pulled the engine from donor bike. Weight comparison – YZM weights in at 54 lbs. and production engine came in at heavy 61 lbs.

I am currently working on modifying the frame and fabricating the custom exhaust. The engine is twin exhaust port, so the exhaust. has to be made custom. Production bikes are single port. As for the frame, The front down tube is notched for dual exhaust and left rear down tube must be modified due to the fact that the intake and carburetor are at different angle 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.

Build details:

1998 YZ400F donor bike. Frame, swingarm, seat pan, forks, lower tripe tree, hubs and calipers is about all that remains.

Titanium factory rear subframe

Titanium foot pegs.

90% of fasteners are titanium. 100% of Engine fasteners are titanium.  Many components on the engine are billet titanium. Really!

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 will be using a new programmable DC-CDI ignition system by Zeeltronic and utilizing the original prototype stator and flywheel.

Carburetor will be an original production Keihin CR but with some modifications. I’ll be using the throttle position sensor since the programable CDI uses 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.

Radiators will be modified Fluidyne aluminum oversized. Needed for this engine, since the engine is wet sump with less than quart of oil.

New Excel rims

New 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

New Cables customized

New Pro Taper fat handle bars. Same ones used by Doug Hemry

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

This is Andrea Bartolini YZM400F

Bartolini YZM400

Bartolini works

This is the YZM400 Electric

1997 YZM400 Prototype Electric Start

Below  is a photo of Doug Henry’s YZM400F. Same engine minus electric starter

Doug Henry's YZM400F

This is a article in Dec 1997 Dirt Bike magazine wit Stephane Peterhansel holding this engine.

Dirt Bike Dec 1997 article on YZM400F with electric start.

YZM400 Clutch side

Doing quick fit of YZM400 in the donor bike.

Fitting YZM400 into the donor bike

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

Donor bike being modified for YZM400 engine

Look familiar? I made a actual size copy of Doug Henry frame down tube as a template.   You can put the photo template in front of the frame, take it away, and you will not see a difference.

Donor bike frame modified to fit carberator

Things are being fitted up first and then the final welding. Here you see the frame is notched for dual output exhaust. The factory YZM frame was built with a front wish portion of frame to allow for exhaust output.

Yet another overlook detail. The sprocket cover is billet titanium

YZM400 1997

I had some of the original graphic decals custom made.

YZM400 Decals and custom seat

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

YZM400F plastic

This the rear sub-frame I’ll be using. All titanium. Spoke with Mark Jerman. He use to make these for Yamaha when her worked there on the YZM project.

Titanium Sub frame YZM400F

The orignal YZM400F used larger radiators. I’ll be installing a set of Fluidyne custom radiators.

Along with NOS YZ400F air louvers with custom extensions.

Fluidyne Radiators for YZM400F

DRD Doug Dubach Racing carbon fiber muffler, custom made to match the Henry / Bartolin bikes

Added a Carbon fiber air box

DRD Doug Dubach Racing carbon fiber muffler YZM400

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

Billet Titanium side cover

Titanium Cover

Carbon Fiber Engine mounts

Carbon Fiber Engine mounts

Click here for YZM400 Electric Starter Test

Bench tested Zeeltronic programmable CDI unit. Pickup coil and throttle position good.

Produced spark with high tension coil.

Due to the slight difference in engine from production and longer intake manifold

the carburetor air boot had to be shorted. Modified vs. Stock on right

Modified Air Box boot

Fits pretty good!

Carburetor Air boot

Completed fabricating the battery box which also holds starter relay.

Fits nicely under the seat inside the air box. Still plenty of air for carburetor.

Battery Box

Exhaust Frame Cut Away YZM400

Twin Pipe Exhaust YZM400

Now we do the build. Assemblies ready. We go for paint and put it together.

Modified 1998 YZ400F frame to YZM





Still a lot of work to do but I thought I would do a dress rehearsal.


2013 YZM400 Completed 12/7/2013

Click here to see First Test run  TEST RUN

YZM400 Electric Start

YZM400 Yamaha



YZM400 Dubach Racing DRD Carbon Fiber Custom


YZM400 Titanium Cover


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