Street-Legal Smoker: Yamaha MX360

Streetable Endurocrosser from Germany’s Loose Screw…  

In 1968, Yamaha hit a home run with the original DT-1 250 — an affordable, lightweight, street-legal two-stroke dirt bike that not only sold out in short order, but essentially created what would become the dual-sport category. In the years after the bike’s launch, there were rumors of an open-class machine in the works, which appeared in 1970 as the RT-1 360.

Yamaha later simplified their off-road naming conventions, using DT360 for the street-legal endurocrosser and MX360 for the off-roader. By 1973, the MX frame had been redesigned with an eye toward the top European motocrossers, with an engine making nearly 40 horsepower.

“The 360’s wheelbase, for example, has been stretched out to that of a radially finned 400 Maico. Weight distribution and ground clearance are virtually identical to a 400 Husky CR. The all-new engine is smoother than any of the competition, thanks to an omni-phase balancer.” –Cycle World, 1973

While they weren’t the lightest or nimblest ‘crossers of the era, if you’ve ever ridden one of these big-bore twin-shock brutes, you know they produce a grin a minute — and nothing beats the smell and sound of a vintage two-stroke.

This ’73 MX360 comes to us from Enrico of Munich’s Loose Screw, a workshop that specializes in vintage and custom motorcycles of all kinds. 

“It all started over 15 years ago when we rode 400km from Munich to Lake Garda on old converted 50cc mopeds.”

After that, Enrico bought and rebuilt a Yamaha XS400, got his motorcycle license, and the rest is history. While we’ve only showcased one Loose Screw in the past — a custom Honda XL500 — Enrico’s shop has had a hand in several of the German and Austrian builds we’ve featured over the years.

Street Sweet, Dirt Worthy: Honda XL500 by Loose Screw

The bike was built for friend of the shop Felix, and the idea was to transform the old MXer into a road-legal enduro with classic looks and a touch of custom gusto.

“The aim was to keep the bike in the classic look but still be able to get road approval in Germany, which is why indicators, speedometer, and lights had to be installed. We also wanted it to look classic but not too colorful, and since there is a lot of aluminum on the bike, we opted for the monochrome color scheme.”

This is one of those projects that extended over years, delayed by parts availability, time, and the inertia of trying to push through the last few details…but it’s finally done. Highlights include a rebuilt engine, aluminum tank with understated paint, Motogadget welded into the crossbar (first time we’ve seen that!), tiny Kellermann Atto blinkers, miniature push-button controls, a Sattlerei SAM seat, modified Husky exhaust, and many NOS and period-correct parts.

The result is one of the cleanest twin-shock endurocrossers we’ve seen…and it’s for sale! If it weren’t on the other side of the Pond, this is one smoker we’d love to have in the BikeBound stable. Below is our uncut interview with Enrico about the build, along with more images from Gusti Auer (www.augustauer.com).

Yamaha 360 Enduro: Builder Interview

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

Hello, I’m Enrico, now 42 years old, and I have a small workshop near Munich, the “Loose Screw”. It all started over 15 years ago when we rode 400km from Munich to Lake Garda on old converted 50cc mopeds. After that I quickly got my first motorcycle, an XS400, which was completely rebuilt, and when it was finished I also got my motorcycle license to be able to ride it. This was followed by some of my own projects as well as several customer bikes.

The “Loose Screw” is primarily about old motorcycles or custom-made/conversions of all kinds. Sometimes creatively unusual, sometimes simple in the original look.

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

It’s a Yamaha MX360 from 1973.

• Why was this bike built?

It was supposed to be a personal bike for a friend, Felix.

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

The bike project started a few years ago. The aim was to keep the bike in the classic look but still be able to get road approval in Germany, which is why indicators, speedometer, and lights had to be installed. We also wanted it to look classic but not too colorful, and since there is a lot of aluminum on the bike, we opted for the monochrome color scheme.

And because it’s not intrusive but you enjoy looking at it, the last few jobs have somehow always been put off. So in recent years, the bike has tended to stand decoratively in shop windows, exhibitions or on a pedestal in our workshop.

But now it was time to complete the bike and, ideally, find a new owner so that we could make room for something new.

• What custom work was done to the bike?

Once a rolling chassis had been found, the real, tedious work began. We were never really satisfied with the parts that were offered and sold to us on the market. So it took us years to complete the engine, for example. We found a fuselage engine that was NOS. Then we were finally able to rebuild the engine. And the project went all the way through. Many original parts, mostly NOS, were sought and bought at auction. Even an aluminum tank in this condition took us quite some time.

• Engine completely overhauled
• Aluminum tank
• Motogadget speedometer embedded in cross brace
• Kellermann Atto indicators
• “LooseScrew” mini push button unit on handlebars
• Modified 125cc Husqvarna exhaust
• Seat from Saddlery SAM from Munich
• Many NOS parts or accessory parts from that time
• All other parts have been completely overhauled and refurbished

• Does the bike have a nickname?

Not really. When we talked about the MX, we all knew what it was about.

• Any idea of horsepower, weight, and/or performance numbers?

Weight: +-106kg
Horsepower: circa 39hp

• Can you tell us what it’s like to ride this bike?

The bike has never been ridden since it was rebuilt. but we have ridden a few 250cc bikes and they are fun to ride but at the same time require a bit of finesse. And anyone who knows the old 2-stroke bikes knows what I mean.

• Was there anything done during this build that you are particularly proud of?

I think in the end you’re proud that this bike is exactly what Yamaha could have done. And that everything harmonizes with each other without being obtrusive. That’s why it made such a good decoration, at home or wherever.

• Is there anyone you’d like to thank?

A big thanks goes to Felix who invested so much time in finding the perfect parts for the project.
Thanks also to Gusti, who took the pictures for the bike.

Follow the Builder

Builder: LooseScrew: loosescrew.de | @loose__screw
Seat: Sattlerei SAM: sattlerei-sam.de | @sattlereisam
Photography: Gusti Auer: www.augustauer.com