Straight Outta Sanctuary: Honda CB1100R Restomod

Possibly the Last: Honda CB1100R from AC Sanctuary… 

In 1980, Honda unveiled their first-ever homologation special, the CB1100R. Based on the CB900, the single-seat sport bike boasted a 1062cc 16-valve DOHC inline-four producing 120 bhp and was designed for endurance racing, where it made an impact straight away.

“The 1100R began life as a batch of 100 homologation specials, eight of which lined-up on the grid for the model’s maiden race, the six-hour endurance event at Amaroo Park, Australia.” –Motorsport Magazine

That Australian event was the renowned Castrol 6 Hour race, and none other than Wayne Gardner and teammate Andrew Johnston took away the win. In fact, the organizers would bar the CB1100R from the 1981 race, deeming it a “race special” instead of a production bike.

No matter, the CB1100R would race successfully on several continents, and the road-going version was soon available (albeit not in the USA). The bike was an instant classic, the fastest production bike of its time, and one of the first proper race replicas from a major Japanese manufacturer.

“The Honda CB1100R is one of the select few no-compromise, high-speed motorcycles — machines that express, in visceral as well as functional terms, that their riders are humans of unusual two-wheeled discrimination. Of the roadrace-oriented specials in its class the Suzuki Katana, the Eddie Lawson Replica KZ1000R, and the one-liter Bimotas — only the Italian kit bikes approach the level of visual flash and exclusivity embodied by the Honda.” –Motorcyclist, 1982

Only around 4000 examples were ever made, with slight differences between the CB1100RB (1980/81), CB1100RC (1982), and CB1100RD (1983).

Of course, you might have noticed this ’93 CB1100RD is far from stock. It’s the work of none other than Hiroyuki Nakamura of AC Sanctuary, and it’s been given the full RCM (Radical Custom Manufacture) treatment.

The Japanese workshop is best-known for their Kawasaki Zed models, such as the KZ1000-powered A16R we featured last week, but they have tackled their fair share of Hondas…and this one came their way at an affordable price.

“The team decided to ‘build it however they like’ as a new demo vehicle for RCM craftsmanship at their sanctuary, but when they started work, T.M. [the client] came forward and said he wanted to buy it.”

Nakamura-san says these Honda builds do pose a challenge from a parts availability standpoint — spares just aren’t readily available like they are for the Zeds, especially when it comes to internal engine components. Only the team’s stash of carefully collected components made the build possible, so this project is both extra special and a bit bittersweet…

“I don’t know if I’ll be able to make a CB1100R RCM in the future, so I thought there was no point in holding on to it, so I decided to go ahead and use it… But the precious stock parts I had on hand have been depleted considerably, so for some reason I feel a bit sad…” -Nakamura-san

Nakamura says the engine was fully processed by the good people at DiNx, one of AC Sanctuary’s trusted partners for engine rebuilds.

“The crankshaft is journal-wrapped and dynamically balanced, and the cylinder is bored and then honed with a Lotterer H85A to achieve precise clearance.  The valve guides are replaced and the seats are cut to ensure uniformity, with a focus  on precision.” -Nakamura-san

The engine was then fitted with a gorgeous Nitroweld titanium exhaust. The front fork is an ExM package with Öhlins inverted forks — a special package released from AC Sanctuary’s parent company — and the bike is rolling on 17-inch OZ Racing wheels and Brembo brakes.

“17-inch wheels…are a perfect match for the CB1100R, which has a roll axis with the head pipe positioned lower on the frame than the CB-F series!” -Nakamura

Of course, frame modifications were made to accommodate the wider yet smaller-diameter wheels, including a shift in the angle of the rear shocks and the fitment of a Sculpture swingarm with a width of 295mm.

Nakamura says that while the exterior coloring may appear standard at first glance, it’s actually a “slightly twisted” design wherein the red and blue are candy colors with slightly darker tones, and the logos on each part are painted on — not vinyl — for a higher quality finish. They also chose to reupholster the seat in black instead of the standard red, as red shows dirt too easily.

The upper cowling was lowered 10mm along with the cowling stays, and the screen was cut by hand. Nakamura says this makes the “face” of the bike look slightly smaller, “which is really cool.”

The cockpit contains a triplet of gauges from Stack, set in a one-off carbon fiber instrument panel made specifically for this build. The electrical system was completely revamped according to modern standards, and the build took a total of two years…partly due to the difficulty of procuring parts.

This CB1100R restomod is nothing short of incredible, but Nakamura fears the impact of rising prices and limited inventory both for donor bikes and replacement parts.

“In the future, it will become increasingly difficult to realize RCMs for classic bikes, let alone the air-cooled Z series. To be honest, the CB1100R is particularly difficult, and at this stage I honestly believe that this RCM-630 may actually be my last.”

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More AC Sanctuary Restomods…

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