SR400 Reborn: Yamaha “SR540MX” Tracker

The People’s Choice: 540cc Dirt Tracker from GM Motorcycles… 

The Yamaha SR400 remains one of the most beloved machines in motorcycling. It arrived on the scene in 1978 as an easy to ride single-cylinder street version of the XT500, which won the inaugural Paris Dakar Rally that same year. The SR would remain in production for nearly half a century, becoming a favorite of riders and custom builders all over the world. Yamaha finally said goodbye to the beloved model in 2021, making it one of the longest produced models ever, but the SR remained true to its roots to the very end: air-cooled, twin-shock, and kickstart only.

Yamaha SR400 TrackerSo when Giovanni “Gio” of Sydney, Australia’s GM Motorcycles saw an ’88 SR400 languishing in the salt air of a restaurant parking lot — a bike that had obviously been sitting there for several years — he had to rescue it. In the end, the owner let the vintage thumper go for a mere $1. The bike sat in Gio’s garage awaiting its fate until the advent of The Machine Show 2024, an Australian bike-building competition that required a pre-90s bike. The time for the SR’s resurrection had arrived.

Yamaha SR400 TrackerGio had just six months until the show, but his vision for the build was clear:

“I’ve been getting into Australian dirt track racing so the vision was to create a show bike that could also tear up the track. I wanted more power and a slicker riding experience while retaining the beauty of the SR and paying homage to its history.”

Yamaha SR400 TrackerStill, he had only a rough idea of how he wanted the bike to look, and there wouldn’t be much time for mistakes. His modifications were incredibly ambitious, and he estimates he put more than 400 hours into the build. 

Yamaha SR400 TrackerGio gives us the full rundown of the build below, but let’s mention a few of the highlights. First there’s the one-off aluminum bodywork he hand-shaped at MotoRRetro, which includes the front mudguard, tail section with integrated sideboards, fork covers, bash plate, chain guard, front number board, and more. 

“The metal work was done at MotoRRetro, I couldn’t make this project a reality without their knowledge and equipment.”

Yamaha SR400 TrackerUp front, there’s a set of YZ250 forks with a custom steel steering head bearing cup Gio made himself. Out back, a YZ250 swingarm with monoshock conversion, and the bike is sitting on 21″ front / 18″ rear Excel rims with Michelin rubber.

“This wheel size/tyre setup is what is used for Australian dirt track racing.”

Yamaha SR400 TrackerThe engine has been punched up to 540cc with a Wiseco high-comp piston and XT500 crank. The head was ported, and the big-bore thumper now breathes through a Keihin pumper carb and custom undertail exhaust.

The frame was powdered Illusion Purple — a Prismatic Powders color — and the graphics were designed by Cam Rogers and Luke at Deus Ex Machina Sydney to match the Yamaha YZ250 50th Anniversary style.

Yamaha SR400 TrackerThese elements are just the tip of the iceberg. Everywhere you look, you’re sure to notice more design and fabrication work. It’s incredible that Gio was able to build this bike in such a short time, and to such a high standard. Not surprisingly, the “SR540MX” took home the People’s Choice award at The Machine Show — go, Gio!

Yamaha SR400 TrackerBut this is no mere show pony — Gio is proud of how well he built the bike to perform, and he’ll have it on the track soon.

“I considered the values of both performance and presentation equally so it’s hard to choose one over the other. Ultimately it’s a race bike that’s been made to win a custom competition where only appearance is judged… So I guess what I like best is the balance; that it doesn’t prioritise appearance or potency — it rides as well as it looks.”

Below, Gio gives us the full story of the build in his own words, and we’d be remiss not to mention Cameron Rogers (@cam.rogerss) of Deus Sydney for the stunning shots of the build.

In the Builder’s Words…

Yamaha SR400 Tracker

The story of this bike:

In 2018 I was walking back from a day at the beach when I noticed a very sad looking SR400 sitting in a restaurant car park, rotting in the salty air — I knew it deserved a better life. I went into the restaurant to find the owner and ask if it was for sale as it was obvious that it’d been sitting there for several years. After a few days of emailing back and forth, the bike was mine for $1.

The donor
When/why I decided to build it:

She sat in my garage for five years, until 2023 when The Machine Show, an Australian custom bike-building competition was announced and a pre-90s bike was required. I knew it was finally time to bring it back to life.

The vision:

Over the past few years I’ve been getting into Australian dirt track racing so the vision was to create a show bike that could also tear up the track. I wanted more power and a slicker riding experience while retaining the beauty of the SR and paying homage to its history.

Yamaha SR400 Tracker

The event:

Over the past 4 years The Machine Show quickly earned its spot as one of the truly great shows on the custom motorcycle calendar. Matt, the organiser, creates an awesome annual event which is basically a “vintage motorcycle camp-out weekend.” A symphony of incredible custom bikes and cheerful chatter, interspersed with fantastic food and beverages. The SR540MX won the 2024 people’s choice competition.

The build process:

The timeline was the hardest part, I smashed out this build in six months. I had a rough idea of the look I was after but absolutely no time to design or make mistakes — which is a rough combo. So basically I designed as I went and solved issues as they arose — it was a fun process.

In total around 400 hours went into actualising all of the ideas I had, as I really didn’t want to compromise, cut corners, or leave any details behind. Most of my time went into the metal shaping as I painstakingly re-moulded the original tank and created from scratch all body parts which are all one-of-a-kind single pieces hand-shaped in aluminium.

Yamaha SR400 Tracker

The metal work was done at MotoRRetro, I couldn’t make this project a reality without their knowledge and equipment.

What it actually is:

FRONT END
I wanted to bring the bike into the 21st century by updating the forks with a fully customized front end from a YZ250 ‘02, but I didn’t want to compromise the original frame to fit the new triple clamp. So to keep everything as standard as possible, I opted for creating a steering head bearing cup instead of modifying the frame or the steering stem.

Yamaha SR400 Tracker

I made the cup with Chrome-Moly high tensile steel. Now the YZ250 forks can be clamped right where they should be from the factory, on a SR400 standard frame. The forks have been lowered 100mm with new heavy duty springs and valves.

Yamaha SR400 Tracker

REAR END
My original vision was to keep a twin-shock configuration as standard on the SR400 and modify the YZ250 swingarm from single to twin. Unfortunately my creativity took over, creating a tail fairing so narrow that couldn’t fit the twin shock top mounts.

Yamaha SR400 Tracker

Plan B was a Ducati Supersport 939 S ’22 Öhlins shock which happened to be patiently awaiting its fate in my garage. A great compromise. The YZ swingarm has been slightly modified while the SR frame has been converted to single shock setup.

Yamaha SR400 Tracker

Now the frame has a bracket at the bottom to hold the swingarm links while the top shock mount style is inspired from a BIMOTA frames book which I also had sitting around.

WHEELS SETUP
Excel gold rims, stainless steel spokes, OEM YZ250 powder-coated hubs. Rear wheel diameter was reduced to 18” to fit the legendary Michelin Trial Competition X11 tyre. Front rim is standard 21” with a Michelin Starcross 6 medium soft tyre. This wheel size/tyre setup is what is used for Australian dirt track racing.

Yamaha SR400 Tracker

BODYWORK
I sculpted some knee dents into the stock tank as well as indents at the front for the forks to clear; the dents balance out perfectly and she is now truly one of a kind.

Also, I created out of 1.6mm aluminum sheet a single-piece front mudguard, tail section which includes the sideboards, fork covers, bash plate, chain guard and front number board.

Yamaha SR400 Tracker

FOOTPEG MOUNTS
The thicker YZ250 swingarm is mounted lower compared to the original, so the top factory footpeg mount couldn’t be used any more. New brackets have been made to fit YZ footpegs and rear brake system to the SR modified frame.

Yamaha SR400 Tracker

ENGINE
The 400cc engine is now 540cc thanks to a +3mm diameter Wiseco high compression forged piston and a new XT500 crankshaft. The cylinder head has been ported to increase the airflow into the combustion chamber to make more power. This SR400 engine won’t feel the same. Top end of the motor is vapour-blasted while the bottom has been painted in black to match the swingarm. The logo on the kick start indication cover cap has been laser engraved.

Yamaha SR400 Tracker

CARBURETOR
I updated the carburetor to a 39mm Keihin Pumper Carb from a YZ250F 2010. Much bigger in body volume than the original meant I needed to make space. So I made a new intake manifold and notched the frame at the back of the carby to make it fit perfectly.

Yamaha SR400 Tracker

EXHAUST
I wanted the muffler under the seat for a streamlined look, but to do this while still achieving the best performance, I reshaped the pipe around the frame with the fattest radius possible to maximise exhaust gasses speed.

Yamaha SR400 Tracker

The header pipe is made in one piece to straight fit a Leo Vince muffler. The carbon fiber heat shield has been created in two pieces to protect the rider’s leg at the outside and to reduce the hot air reaching the air filter on the inside area.

Yamaha SR400 Tracker

Inspiration behind the choice of colour:

I did some research about Yamaha factory team colors from the 80’s and 90’s…but found nothing interesting or unique, mainly just colours that have been repeatedly used in so many other builds.

Then one day I went to pick up some parts at a local yamaha dealer and I saw a brand new YZ250 50th anniversary in purple and white similar to some other Yamaha’s in the early 90’s. I fell in love with those colors straight away and knew I must include them.

Yamaha SR400 Tracker

For the frame and triple clamp powder coating I’ve picked a special color from Prismatic Powders. While standard colors consist in two layers (primer and color), the ILLUSION PURPLE has four layers: primer, chrome, purple and clear.

Yamaha SR400 Tracker

The swingarm, handlebars, and wheel hubs are powder-coated in black. The graphics have been designed by Cameron Rogers and Luke Ebert at Deus Ex Machina Sydney to match the YZ250 50th anniversary style.

Favourite thing about the bike:

I considered the values of both performance and presentation equally so it’s hard to choose one over the other. Ultimately it’s a race bike that’s been made to win a custom competition where only appearance is judged.

At first glance the original core is all intact, however once you zoom out you’ll see so many modifications that take it to the next level in terms of power and handling. So I guess what I like best is the balance; that it doesn’t prioritise appearance or potency — it rides as well as it looks.

How’s the bike ride:

I held myself back from riding the bike before the competition which was so hard. But now that The Machine Show is over, I’ll take a track day to test it properly, but also I’m planning to add some extra parts to use it on road. It deserves to get out more often.

From the little celebratory ride I had, I could tell it’s crazy quick compared to a stock engine configuration. The original tank tricks you into thinking that you’re on an SR but with the new geometry and suspension setup you know you’re on something modern that you can trust while testing your riding limits.

Finally…

In the end I shaped and attached an Australian dollar coin to the handlebar. It’s a lucky charm and a reminder of where this all began.

Yamaha SR400 Tracker

Build Sheet:

  • Yamaha YZ250 2002 KYB Forks (lowered 100mm), swingarm, wheel hubs (laced to gold Excel rims with stainless steel spokes), foot pegs, hydraulic front and rear brakes.
  • Ducati Super Sport 939s Öhlins shock
  • Yamaha SR400 1988 tank modified with scalloped knee and fork indents
  • Yamaha YZ250F 2010 39mm KEIHIN Pumper Carburetor
  • Hand formed front fender, tail section, front plate, fork covers, splash guard, bash plate, chain guard
  • Gripper seat covered by Bad Arse Trim co
  • Graphics designed by Cam Rogers and Lule at Deus Ex Machina Sydney (Yamaha YZ250 50th anniversary style)
  • Wiseco big bore high compression forged piston (11:1)
  • Yamaha XT 500 crankshaft
  • Modified cylinder head
  • Handmade exhaust mated to Leo Vince muffler, custom carbon fiber heat shields
  • Braided brake lines
  • Metal Master brake rotors
  • Rear tyre 18” Michelin Trial Competition X11
  • Front tyre 21” Michelin Starcross 6 medium soft

Follow the Builder

Instagram: @gm.motorcycles
Photos: Cameron Rogers (@cam.rogerss)

9 Comments

  1. Elam Blacktree

    Nicely done!

  2. ORWinElCajon

    Xlnt & I’d love to ride it !

  3. Wow. Beautiful bike, impeccable attention to detail. Almost too pretty to race.
    The headline confused my USA-centric brain, tho. “Tracker” is always shorthand for low-slung competition bikes like the H-D XR-750 and the lot, with “street tracker” as a barely legal imitator. Looks like Australian dirt track racing is an entirely different thing, since this custom looks much more like a motocross bike…at least to me.

  4. Unfortunately part of this article is wrong. The XT500 was the street version of the TT500. The TT was not street legal at all and the XT had all the accoutrements to make it streetable. I know this because I owned a 1978 XT and converted it to a TT. I raced it in an “over 40” moto-x class and used it on trail rides in the Rampart Range area if Colorado. It was not competitive in motor cross, but it was fun and it was very capable chasing jack rabbits on the prairie or riding mountain trails. The XT and TT Yamahas were great motorcycles. I wish I had mine back – sold it in 1989 for $350.00.

    • You are indeed correct that the XT500 was the street-legal version of the TT500. But the XT500 was a dual-sport and the SR500 was an even more street-centric version based on the XT500.

      • “The SR500 was the road-going version of the Yamaha XT500, an indestructible off-road motorcycle that is best remembered today for its dominance in the early days of the grueling Paris-Dakar Rally – winning the first and second editions of the event in 1979 and 1980.” -Silodrome

        “The SR’s basics are well known. In 1976 Yamaha introduced the XT500 and TT500, dual-purpose and off-road-only Singles. Many buyers converted the XTs to road-only and added stuff like downpipes and low fenders and narrow bars. More people than that thought about it and so Yamaha decided to do the job, well, properly, the factory naturally having the resources required for a first-class conversion.” -Cycle World

  5. was not the 400 a result of the European license classifications that did make it to USA on a gamble and was obviously very successful? This bike is an extremely fine build and should be a real treat to ride. The engine should be a torque monster and rocket out of turns 2 and 4, and back into turns 1 and 3 like the old 60s no brakes style just for fun once Gio gets a 2 to 3 second lead over the rest of the pack. Thank you for this excellent article.

    • As we understand it, the SR400 was built originally for the Japanese Domestic Market for their 400cc licensing restrictions and later introduced here and other markets. Some folks actually prefer the rev-happy short-stroke character of the 400 over the 500. Of course, we’d choose a 540cc big bore like this one all day 🙂

  6. Dave Harbison

    I have a 79 XT 500 The white one I currently ride now I have a 77 XT 500 the brown one I have two more frames with kind of scrappy parts but the rims in the swing arms and the shocks are good. The wiring is gonna need updating and I would love to build a bike like that SR 500 that thing is so sick I want one just like it, but in my colors in my way that would be so cool but I’m running out of time. I’m 60 years old and I have a 27-year-old son that hopefully will take my place and finish my bikes for me. Love your bikes🤘 biker Dave

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