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Knockout: Bolt’s custom R100RT boxer

1981 BMW R100RT cafe racer by Bolt Motor Co.
A new build from Spain’s Bolt Motor Co. is always a treat. The Valencia-based workshop has a history of high-end racecar preparation, and they like to eke out maximum performance from their two-wheeled builds as well.

Shop owner Adrián Campos has a particular affinity for BMW airheads, and his latest creation is based on a 1981 R100RT. That was the touring version of the RS, and in its day, the most expensive production motorcycle you could buy in the States.

1981 BMW R100RT cafe racer by Bolt Motor Co.
Bolt have treated this forty-year-old model with respect. The air-cooled 980cc boxer twin has been completely rebuilt and heavily modified, with a twin-spark conversion allowing higher compression pistons and a stronger power output.

Breathing is now via Mikuni carbs rather than 40mm Bings, with gases exiting via straight 2-into-1 pipes ending in a Spark muffler. A Siebenrock Deep Sump Conversion Kit ensures a plentiful supply of oil for cooling.

1981 BMW R100RT cafe racer by Bolt Motor Co.
You just know this engine will run as sweet as a nut—because Adrián’s former race engineer Juan Fernandez built it. (Juan has also worked for the Mahindra Formula E championship team, so he handled all the electrics on the BMW too.)

The rest of the mods are a little more unusual. “On the mechanical side, we installed a hydraulic clutch,” Adrián says. “It’s something rare to see on these models. It’s a kit, but we had to make modifications to the gearbox to adapt it.”

1981 BMW R100RT cafe racer by Bolt Motor Co.
That sounds challenging enough, but the worst was yet to come: Bolt installed the die-cast single-sided swingarm from a R1200S. It meant grafting on part of a R1200S chassis with the Paralever attachments, reshaping the swingarm itself slightly and repositioning the hole for the axle.

Then Adrián’s crew made adaptors to connect the swingarm to the R100 gearbox, and slotted in a race-spec shock made by Hagon.

1981 BMW R100RT cafe racer by Bolt Motor Co.
“The rear frame is designed to look like the seat and the tail are hanging in the air, with no transversal support,” Adrián says. “The tail was designed and printed in 3D, then made in carbon fiber with extra layers underneath to deal with the heat coming from the exhaust.” The unobtrusive seat unit comes from Tapizados Llop Ferrer, a top-class upholsterer based in Valencia.

The front end gets an even bigger upgrade: the front wheel and Öhlins forks from a Ducati Panigale 1299. They’re fitted using a modified version of Bolt’s triple tree conversion for BMW K- and R-series models. Braking is handled by 330mm discs with new Brembo M4 monobloc calipers, and the back wheel is from a BMW R1200

1981 BMW R100RT cafe racer by Bolt Motor Co.
After all this mechanical trickery, the bodywork was the easier part. Bolt bought in a generic fiberglass fairing thinking it would fit—“but we ended up modifying it completely, so I don’t know if it was worth it!” Adrián shrugs.

The tank is actually stock, but has been raised slightly at the back to get a better line.

1981 BMW R100RT cafe racer by Bolt Motor Co.
Electrics are sometimes an afterthought on customs, but not in this case: Bolt’s Juan Fernandez worked with the Barcelona-based engineering and R&D specialist Engiser 101 to create a complete new loom.

It’s hooked up to a Motogadget Mini speedo, a retro-style rev counter, and switchgear from RebelMoto. Foot controls are from the Italian legends Tarozzi.

1981 BMW R100RT cafe racer by Bolt Motor Co.
We reckon Bolt’s R100RT is the perfect way to kick off 2021: a classic recipe, with an extra hit of engineering, power and style. Here’s to a brilliant year of customs ahead.

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1981 BMW R100RT cafe racer by Bolt Motor Co.