– Motorcycle News, Editorials, Product Reviews and Bike Reviews

Motorcycle News, Editorials, Product Reviews and Bike Reviews

Ritmo Sereno: Modifying and Racing Older BMWs and Moto Guzzis (with video)


This bike started life as a late-’80s R 100RS

There are lots of passionate and talented motorcycle enthusiasts out there. Only some of them, however, seem to go their own way … not caring what anyone else is doing or thinking.

One such person is Shiro Nakajima, owner and founder of the Japanese bike shop Ritmo Sereno. The bikes he builds, both for customers and for his shop’s racing stable are beautiful, functional and fast (faster than the bikes they are based on).

Nakajima’s personal race bike is a modified Moto Guzzi Ambassador. He races against other classic bikes in a series in Japan. Ritmo Sereno’s main shop is in Tokyo.

To highlight some of the work Ritmo Sereno does, here is a list of modifications to a late-1980s BMW R 100RS (excuse the Google Chrome translation of the native Japanese):


Former MotoGP racer, and test rider, Shinya Nakano aboard Nakajima’s personal race bike.


The starting point for the R 100RS modified bike.


Brembo four-piston brake calipers

Custom content

underbody and body around 
● Showa 41φ front fork 
● stem and top bridge processing diversion 
● one-off steering stem 
● Orleans rear shock 
● diversion front hub processing 
● 300φ floating disk 
● Brembo 4pot caliper 
● one-off disk spacer 
● before and after cast → spoke wheel of 
● Excelsior H rim 
● frame powder coating

Engine & mission 
● full overhaul 
● high cam 
● FCR carburetor K & N filter 
● stainless steel exhaust pipe 
● diversion silencer two production 
● cylinder and head cancer Court 
● Other cases blasting


Custom gauges and cockpit

Electrical system 
● ENDURA last alternator 
● Dyna coil Taylor plug cord 
● stack Clubman tachometer 
● digital speedometer 
● Japan electrical cell made of motor

Operation system 
● Nissin radial master 
● left and right step pedal such as one-off production 
● Tomazeri throttle 
● original accelerator wire

Exterior other 
● original double sheet 
● Newton tank cap processing mounting 
● Aluminum battery case one-off production 
● aluminum oil catch tank one-off production 
● aluminum meter panel one-off production 
● diversion front plating fender 
● Aluminum rear fender 
● other various parts production

Below you will find a short video featuring Nakajima, followed by additional pictures of some of his bikes (note the Öhlins forks and Brembo brakes on the BMW in the last picture).


Modified R 100RS


Nakajima’s personal Moto Guzzi Ambassador


Highly modified air-cooled Boxer

See more of MD’s great photography:



  1. Gary says:

    If you’re going to race an airhead Beemer, you damned sure better brace that frame. Otherwise you will wobble like a weeble.

  2. Gary says:

    Seriously? This is news worthy? I see better adaptations of vintage BMWs/Guzzis by local bike owners at most of the yearly meets. Forgive me but I’m not being bowled over by any novel innovation or creativity here. There are a lot of people who want to label themselves as “builders” these days, who aren’t really bringing anything new to the table.

    • Dirck Edge says:

      The difference is you only look at the pretty parts. This guy is improving the engine, chassis and braking of these older bikes without sacrificing their vintage style (in fact, improving it). Few custom builders give a damn about improving performance, except, perhaps, thinking a loud exhaust system does something.

    • Jeremy in TX says:

      I like the modest aesthetic treatment personally and to see all of the original functionality preserved while tacking on engine and chassis improvements as well. That is a thing of beauty in my opinion. Many builders put things together that look great to the eye, but their ultimate goal is almost always form over function. What these guys are doing speaks to me.

  3. Kent says:

    Old bikes are cool. Seems like most of the advances over the decades have been just bigger/faster/louder. Not necessarily better.

  4. Frank says:

    You go Ritmo….all beauties!

  5. Provologna says:

    That black modified R100RS is a beauty.

    In the 80s, used air heads ran around $1500 in moderate condition, in the San Francisco Chronicle classifieds.

    A few years ago my friend said they were going for around $10k.

    My black stock early 70s R90 w/Don Vesco designed Windjammer SS was geared higher than a kite. Barely over 3k RPM @ 65-70mph indicated. I rang its neck and could not get less than 50mpg, even two-up flying well past the speed limit from SF to Disneyland. Torque up the wazoo, and suspension compliance the Japanese could not build if their life depended on it (at least in that era).

    The tail trunk on that bike caused it to wheelie like crazy in the first two years.

    • Kbasa says:

      Actually, Craig Vetter designed the Windjammer. Vesco designed the Rabid Transit fairing, which is probably what you’re thinking of. 🙂

  6. ROXX says:

    I love this story.
    Especially being that my main ride is a 99 BMW R1100S.

  7. MGNorge says:

    Very cool! The Ritmo Sereno certainly looks to have a big ol’ lump of Guzzi engine with Nakano aboard. Very cool indeed!

  8. Denny says:

    There is a sizeable following of classic European bikes in Japan. Some time ago I have seen a video of group of vintage BMW owners – quite impressive. Just as we like their bikes, it’s mutual – exotica pulls.

  9. John says:

    I like it a lot but would want to keep the RS fairing, and have him work a miracle with it not yank and drop in a bikini plexi shield.

    I am guessing this is costing oh say half my net worth, and I am a veteran salaryman in USA.

    Admire him.

    • Ax1464 says:

      Exactly. The different fairings were what differentiated the R100, R100S, R100RS and R100RT. I hate seeing those fairings “tossed to the side” so the underlying bike can be customized. Surely bare R100’s are more plentiful and easy to find than RS’s.

    • stinkywheels says:

      I’m with you. The new RS isn’t as groundbreaking as the original RS. The undisputed king of the dead engine races down Rabbit Ears Pass!

  10. yellowhammer says:

    Is this somehow tied in with the release of the new Godzilla movie next week?

  11. mechanicus says:

    So, let me get this straight – a guy in Japan has a motorcycle repair shop and rides a Moto Guzzi? Nahh, really?

    • Randy Dawes says:

      FYI, Moto Guzzis are in Japan and have many fans who ride theirs. They are very proud of their bikes. Tho I have to say making an Ambo. look like a racer is more for image than practicality.

  12. Cyclemotorist says:

    Those bikes are incredible!

  13. Tank says:

    “Ritmo Sereno” sounds like a Mexican bar in Laredo.

  14. Trent says:

    Those are beautiful bikes.

  15. mickey says:

    Shoot I saw that top pic of the BMW and thought BMW was coming out with a true retro and got all excited. Ends up it was a true retro alright, but an old one lol.

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