“Renovatio”: Bultaco Frontera 370 by Nitro Cycles

Bultaco Street Tracker

Bringing a two-stroke Spanish Bul back to life…

In 1975, Bultaco introduced the Frontera, a two-stroke enduro built to meet the demands of “American Enduro experts.” Advertisements appeared in Cycle World and other publications:

“Imagine the lightest quickest Moto-Cross Bike made…then add lights, wide ratio gearbox, and a list of features never before available on a single motorcycle…”

Bultaco Street Tracker

The bike had 6.5 inches of rear travel, 10.2 inches of ground clearance, shoulderless alloy rims, built-in bash plate and toolbox, and weighed just 229 pounds — the lightest in its class. Then, in the 1977 International Six Days Trials (ISDT), the entire three-man US Bultaco team took home the gold on hybrid machines built in California out of Frontera and Pursang parts.

Bultaco Street Tracker

As a small company, Bultaco could react quickly. Immediately, they had the medal-winning machines shipped back to the factory, where they went over them with a fine-tooth comb. Within two months, 250/370 Fronteras patterned after the ISDT race machines were rolling out of the factory. Said Cycle magazine of the Mk. II:

“We didn’t expect the Fronteras to be as good as they are, but it’s all true…it’s the trailbike supreme.”

Bultaco Street Tracker

Enter Antonio Testillano of Spain’s Nitro Cycles, who says of his family workshop:

“We are a family moved by fuel. Our relationship with bikes and cars is an absolute madness. Specially with classic ones. We try to build them lighter and faster!!”

Bultaco Street Tracker

Earlier this year, we featured the shop’s badass V-Max restomod. Now Nitro Cycles is back with this stunning Bultaco Frontera 370 street tracker, which combines the heritage and two-stroke charisma of the original machine with modern wheels, brakes, and suspension. Antonio calls the bike “Renovatio,” since the donor was in rough shape and they completely restored the engine, bringing the old Spanish Bul back to life.

Below, we get the full story on this staggering two-stroke street tracker, along with a killer deck of shots from photographers Diego Bermu and Miki Poveda.

Bultaco Frontera Street Tracker: Builder Interview

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

I started building motorcycles five years ago, but I always tried to make my own cars and bikes different. That’s why my family and I started with this adventure, building bikes as a professional workshop.

We are a family moved by fuel. Our relationship with bikes and cars is an absolutely madness. Specially with classic ones. We try to build them lighter and faster!!

bringing the old Spanish Bul back to life.

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

It is a 1979 Bultaco Frontera 370 mkII.

Bultaco Street Tracker

 • Why was this bike built?

It is a customer project.

bringing the old Spanish Bul back to life.

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

The bike is inspired in dirt track and scrambler bikes. We wanted to build it as it was a nowadays bike… wider wheels, suspension, disc brake, etc…

Bultaco Street Tracker

• What custom work was done to the bike?

We made the the exhaust and the silencer, the subframe, license plate, restored the engine (o km) tank and the seat. We have to adapt the front fork, brake system, wheels…

Bultaco Street Tracker

• Does the bike have a nickname?

I call her Renovatio. She was a scrappy bike and we turn her to life!!

Bultaco Street Tracker

 • How would you classify this bike?

Scrambler/ dirt track.

Bultaco Street Tracker

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

Exhaust system and tank.

Bultaco Street Tracker

Action Shots


Follow the Builder / Photographers

IG: @nitrocycles_es
Web: www.nitrocycles.es
Photographers: @diego_bermu_ and @mikipoveda_



  1. Cool bul

  2. Cool bultaco

  3. Craig Schoene

    What bike did the front end come from?

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