For You, Old Fox: Yamaha RD350 Custom

Yamaha RD350 Custom

Cus’Tom Motorcycles rebuilds his father’s RD… 

The Yamaha RD350 was one of the great giant-killers of the two-wheeled world, a two-stroke street machine with a race-bred bloodline. In AMA Class C racing, the RD racers regularly blew away machines with twice the displacement, making the 350 a favorite of club riders around the world, and a 70s Yamaha advertisement showed a downtrodden 750 rider at the bar: Don’t feel bad. You’re not the first 750 rider to get blown off by a Yamaha 350.

Yamaha RD350 Custom

While the two-stroke parallel-twin made just 39 horsepower in stock trim, it was ripe for modification, spawning a whole cottage industry of tuners and parts makers. What’s more, the RD350 could handle well in the bends, at least for a bike of the period.

“The RD 350 is a cafe racer’s delight with its slim, sleek styling, disc brake on the front wheel and a closely-spaced six-speed transmission… On a favorite stretch of hilly, winding road, you’ll find a race-bred motorcycle in a street machine’s clothing.” –Cycle World, 1973

Yamaha RD350 Custom

Our new friend Tom Boissel has been modifying bikes since he a kid racing 50cc machines, and he opened his own workshop Cus’Tom Motorcycle four years ago, located in the countryside near Toulouse, France.

Yamaha RD350 Custom

The bike you see here is a 1973 Yamaha RD350, and a very special one at that. Says Tom:

“It was my dad’s motorcycle, with which he came to pick me up from school from time to time. Hence the engraving: pour toi vieux renard (“for you, old fox”). I inherited it after his death six years ago. I hadn’t modified it until then, but I have a little boy who will be 6-years-old, and it will be my turn to make him dream in front of his school — the cause was valid to modify the inheritance!”

Yamaha RD350 Custom

The modifications were extensive, including the inverted WP fork, brakes, and wheels from a KTM Duke 390. The swingarm is from the RD350’s legendary successor, the liquid-cooled RD350LC. Here it’s been installed upside-down with a custom Shock Factory mono-shock absorber, along with a rear disc brake and lots of one-off custom hardware to make it all work.

Yamaha RD350 Custom

Other highlights include slightly larger pistons, twin 32mm PWK flat-slide carbs, electronic ignition, lightweight rotor, period expansion chambers, a homemade steel tail section with vegetable leather saddle, homemade pegs and foot controls, and much more.

Yamaha RD350 Custom

Tom is still breaking in the new top end, but he’s aiming for a truly giant-killing power-to-weight ratio:

“When it’s finished, we will fine-tune the settings, hoping to get 50 hp for 100kg.”

Yamaha RD350 Custom

Tom’s RD was a finalist at the 2023 Wheels and Waves “Backyard Project” Custom Contest, and we can’t think of a better tribute to his late father — nor a more exciting ride home from school for his 6-year-old son! These are the stories that make motorcycling so special. Bravo, Tom!

Yamaha RD350 Custom: Builder Interview

Yamaha RD350 Custom

• Please tell us a bit about yourself, your history with motorcycles, and your workshop.

I am Tom Boissel, I’m 33-years-old, and my workshop Cus’Tom Motorcycle is in southern France, in the countryside near Toulouse. I started modifying bikes at 12-years-old with my father for 50cc races, and since then I have never stopped.

Yamaha RD350 Custom

My workshop has been officially open for four years ( I’m only one; I do all the work (mechanics, welding, milling, lathing, bodywork, frame, paint, etc.) except the seat upholstery cover and the paint for big customer projects. You can find short movies of my work on my Youtube channel. Next up, I’ve started projects number 24 and 25 this summer on two V-Max 1200’s.


• What’s the make, model, and year of the bike?

It is a Yamaha 350 RD base from 1973.

Yamaha RD350 Custom

• Why was this bike built?

It was my dad’s motorcycle, with which he came to pick me up from school from time to time. Hence the engraving: pour toi vieux renard (“for you, old fox”). I inherited it after his death six years ago. I hadn’t modified it until then, but I have a little boy who will be 6-years-old, and it will be my turn to make him dream in front of his school — the cause was valid to modify the inheritance!

Yamaha RD350 Custom

• What was the design concept and what influenced the build?

I wanted to keep its original line, modernizing it without losing its proportions, keeping a retro side, with a modern touch, leaving it fluid to highlight its mechanics and add a racing side to it, because after all it’s a two-stroke that has the demon of an engine.

Yamaha RD350 Custom

• What custom work was done to the bike?

The original parts that I kept are the engine, frame, and tank.

Yamaha RD350 Custom

The front axle (rim, caliper, fork, and crown) comes from a KTM 390 Duke; it is the White Power brand, of course integrated by me by adapting the original steering column axis of the motorcycle (see YouTube video below).

The front disc is a racing type (NG brake in 320mm floating diameter). And as a detail, a homemade steering column nut. 

Yamaha RD350 Custom

The rear rim also comes from the KTM; it allows you to run a 150 tire to keep the proportions of the bike. To adapt it, it was necessary to change the bearings, redo the internal and external spacers, modify the existing crown holder, and have a custom crown machined.

Yamaha RD350 Custom

For the swingarm, it comes from the mythical 350 RDLC, adapted (upside down). It is modified to accommodate the single shock absorber custom-assembled by the French company Shock Factory.

Yamaha RD350 Custom

They were kind enough to calculate the most favorable shock possible for me (the lever arm being very important due to the kinematics of the assembly).

The rear caliper is adapted via an aluminum plate type fixing + Cus’Tom stainless steel connecting rod, upside down for the ultimate racing look.

Yamaha RD350 Custom

The master cylinder also comes from the KTM (see youtube video on the integration of the rear brake system).

Yamaha RD350 Custom

All the selector and brake pedal controls are homemade. The rearsets also come from the mythical 350 RDLC, as do the two period expansion chambers.

Yamaha RD350 Custom

The steering damper was recycled from a broken-down washing machine and it is adjustable!

Yamaha RD350 Custom

For the engine, all of the intake and exhaust diameters have been slightly increased to fit better with the new mufflers to gain some horsepower in the high revs.

Yamaha RD350 Custom

The original Mikuni diameter 28 carburetors have given way to two 32 mm PWKs with flat slides, adapted by custom-made aluminum pipes at the workshop.

Yamaha RD350 Custom

The old ignition with contact breakers has been replaced with an electronic ignition with internal rotor, allowing for faster revving (less inertia because the rotor is much smaller) and adjustable ignition advance.

Yamaha RD350 Custom

The cylinders have been rebored to accommodate new pistons. The bike is currently running in, when it will be finished, we will fine tune the settings hoping to get 50 hp for 100kg.

Yamaha RD350 Custom

The back shell is made of homemade steel.

It houses a trailer taillight, and a saddle in red and gold-stitched vegetable leather that matches the deep candy red of the bodywork and all of the motorcycle’s bronze washers.

The headlight is a standard model, where I added a small fairing to hide the new counter / tachometer / dashboard.

A small homemade front wheel guard coated in matte black discreetly hugs the tire. The tires are Pirelli Super Corsa in SC2 race rubber to perfect the racing look.

Yamaha RD350 Custom

Finished Bike Video

Follow the Builder

Facebook: Cus’Tom Motorcycle
Instagram: @custom_motorcycle_tom_boissel
Youtube: @custommotorcycle8364


  1. Great bike. I had the 250 cc version before it got stolen in 1979.

  2. Lo scarico a sigaretta mi piace tantissimo, l’occhio mi cade sempre lì

  3. Hello, mike again.
    How’s things going ? Good I hope. Well this time I’m looking to find and possibly buy a Honda XL 500 SB model. Gray in colour. Mid – late 70’s
    I would appreciate any help
    Thank you..

  4. Nicely made Ride!! Simply Love this machine..

  5. Very nice ride. I was a RD fan and guess I still am. Mine was a 1976 RD400C in red. Heavily modded for performance and a little rocket it was. I bought it new for cash when it was next to impossible to find one. $1000 out the door.Rode it practically every day. It was NOWHERE as pretty as this bike but likely faster.

  6. Those PWK carbs want to be level. I suggest modifying the intake runners to angle the carbs level if you have issues with jetting these PWKs. I run these PWK carbs on my RD350 and R5 as well, but am running the OEM intake manifolds so I can keep the carb floats level.

    Fantastic build by the way! I love how simple it is. I am curious what your finished weight is. Please let us know when it is completed and weighed. Great work!

    • Good morning
      yes I see would send the final power when the break-in and the last adjustments will be made
      Thanks for the angle advice.
      I had found 20° max for these carburettors, so I put them at 17°, but if I have to lower them, I would do it
      thank you for your compliments

  7. Twinturbo yashimira Hayabusa

    Let me pay you the ultimate tribute from one bike builder / fabricator to another that b**** is beautiful I mean drop dead sexy oh please oh please oh pretty please let me ride that because only us artists can feel the love and passion that goes into the crafting of the lines and designs of our sculptures this is the 20th century expression of self through creativeness have changed vastly and who knows in 100 years you might walk into an art gallery and find that beautiful piece hanging on the wall

  8. Roland Bouteiller

    WOW I love your work. I am from Toulouse (L’Union) and right now living in California. Grew up loving the RD 350 and later the RDLC.
    Maybe when I come back to see my parents, we can meet over a Pastis or a coffee?
    I myself restored from scratch a 1974 CZ 380cc (2 stroke). I just bought a Z900 RS Cafe.

Leave a Comment

Your email address will not be published. Required fields are marked *