Yamaha XS400 “Roadster” – BikeBound

Revolutionary XS400 from Roman Juriš…  

Launched in 1976, the Yamaha XS400 got here throughout a time when the key producers had been foreseeing the tip of the two-stroke period and turning their consideration to the event of four-stroke road bikes. The middleweight XS was meant extra as a dependable workhorse commuter than a sporting machine, competing towards machines such because the Kawasaki KZ400, Suzuki GS400, and Honda 400 Hawk.

The air-cooled parallel-twin provided 45 horsepower and the bike turned the quarter-mile in 14.58 seconds, quicker than many of the competitors and solely 0.4 seconds slower than Yamaha’s personal two-stroke RD400F. Not dangerous, however the little 400 four-stroker wouldn’t spur any highway racers or canyon riders to wax poetic.

“Neither the quickest in its class, nor the least costly, nor essentially the most comfy. It’s however a good-looking, purposeful and economical bike — simple to take care of, miserly with fuel, and nonetheless aggressive in a hotly contested class.” –Cycle, by way of Bike Classics

Our buddy Roman Juriš of Slovakia, builder of the current KTM 990 Tremendous Duke we featured, picked up this ’84 XS400 as a non-running donor for an in depth construct.

“I needed a easy roadster, clear traces, slim construct, one thing like the nice previous 1976 Laverda 750 or 1967 Honda CB250, however in a contemporary design.”

Most significantly, Roman needed to check a brand new entrance suspension idea he’s been creating, a Progressive Upside Down Fork (PUSDF) meeting meant to reduce dive underneath braking — a system he’s within the means of patenting. There are three patent claims:

1. Progressiveness — for instance, for a 120 mm suspension journey of the wheel, there’s a 60 mm raise within the fork.

2. When springing, the axis of the entrance wheels is pushed ahead and thus eliminates the shortening of the wheelbase.

3. Separation of spring and braking power — the bike doesn’t dive when braking.

Solely the engine and a number of the wiring stay from the unique donor — Roman constructed the whole body from scratch, and the XS is now working a shortened YZF125 swingarm, supermoto wheels, customized bodywork with a stunning pace block livery, and that distinctive entrance suspension meeting:

“The entrance fork is purposefully model new and guarded by a world patent.”

Roman is ready for the chilly Slovakian climate to clear so he can check the brand new entrance suspension system. We will’t wait to listen to the way it goes!

Yamaha XS400 Cafe Racer: Builder Interview

• Please inform us a bit about your self, your historical past with bikes, and your workshop.

I’m a interest bike modifier and I do it for my very own pleasure.

• What’s the make, mannequin, and yr of the donor bike?

Yamaha XS400, yr 1984.

• Why was this bike constructed?

On the finish of 2018, I assumed there’d been no new information in bike entrance suspension for a very long time. I had a attainable answer, however I knew that I didn’t need to set up the brand new entrance fork on a daily bike.

My concept was a roadster with an undermounted engine and a spine body. In January 2019, I purchased a non-riding Yamaha XS400 and began making a very new body and really the whole lot associated to constructing a bike.

• What was the design idea and what influenced the construct?

I needed a easy roadster, clear traces, slim construct, one thing like the nice previous 1976 Laverda 750 or 1967 Honda CB250, however in a contemporary design.

• What customized work was finished to the bike?

I solely used the engine and a part of the wiring from the unique bike. The body is totally new.

The wheels had been initially motard, however they’ve modified hubs and strings. The rear swingarm comes from a Yamaha YZF 125 however is shortened and outfitted with a spring unit positioned within the fashion of a Ducati Scrambler.

The entrance fork is purposefully model new and guarded by a world patent.

The entire design was modeled from clay and the elements are fabricated from fiberglass. The paintwork is within the fashion of Yamaha racing bikes from the seventies of the final century.

 

The muffler is underneath the seat, the on-board instrument is my favourite Koso. The bike is just not road authorized, but it surely has all the weather of a homologated automobile. I needed to show that even a motorcycle with rearview mirrors, flip alerts, and mudguards can look good.

• Does the bike have a nickname?

It has the title Roadster – it’s a tribute to the Jawa 90 Roadster that was produced in Slovakia a while in the past. It was an amazing bike that was forward of its time.

• Any concept of horsepower, weight, and/or efficiency numbers?

The engine is totally inventory. (I want to search out out the load.)

• Are you able to inform us what it’s wish to journey this bike?

The bike is so recent and the climate in Slovakia so chilly that the bike has not but been examined.

• Was there something finished throughout this construct that you’re significantly pleased with?

Entrance fork.

• Is there anybody you’d wish to thank?

To my spouse, for permitting me to work about 3,000 hours on this challenge over 5 years. To all associates who did an amazing job welding, portray and fabric. And to those that didn’t shut the door after they noticed me coming.

Extra Roman Juriš Builds

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