Race to Rebuild the BMW R90/6

The Motorcycle Classics/Dairyland Cycle Insurance 1974 BMW R90/6 Race to Rebuild project finally wraps up — and it’s lovely.

1974 BMW

It's been a long road, but our BMW cafe project rebuild bike is done!

Photo Courtesy MC Staff

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It’s been a long haul “building” the Motorcycle Classics/Dairyland Cycle Insurance Race to Rebuild BMW, and now that it’s finally finished, we’re kind of sad it’s done.  

Why the quote marks around “building?” The truth is, we didn’t actually “build” anything. What we did, however, was take a tired old BMW and give it a healthy injection of fresh parts for a new lease on life. In the process, we also gave it a new attitude, applying the requisite pieces to turn a staid tourer into a café-themed road bike.

Those pieces include the big things that jump out at you like the custom wheels, the replica Ducati 900SS fairing, the R90S low bars, the R100RT gas tank, the bum-stop solo seat, rearsets and the Dunstall-style mufflers. But there are a lot of details that go into a build like this.

It’s the little things …

Those details include items like the minimalist brushed aluminum turn signals and cats eye taillight we sourced from Dime City Cycles, and the very nice San Jose-style fork brace from Brad Phillips at Phast by Phillips.

Other touches include the fiberglass starter cover from Boxer Works, which we had TC Concepts paint to match the bodywork. The fiberglass cover deletes the factory two-piece aluminum cover that also houses the stock air filter — not a problem as we swapped the stock Bing carburetors for a pair of 32mm Mikunis from Rocky Point Cycle, shod with K&N pod filters. That left the issue of the engine breather hose under the cover that normally dumps into the right intake pipe, now gone. We worked around that by fabricating a simple dump can with a rubber elbow sourced from an old Kymco (!) scooter that the stock breather hose plugged into perfectly. A filtered outlet from the dump can allows normal breathing without an oily mess.

We also had Stuart at Custom Coatings powder coat the front engine cover gloss black to match the valve covers and frame. For a final touch we sanded the raised ribs on the cover to bare aluminum to match the valve covers. Nice.

We got our Raask rearsets from Omar’s Rearsets, and while we’ve heard grumbling about Raasks, they’re the only brand we know of made specifically for older airheads. We did have to shim the main mounts to line up properly on the frame plates, and some of the supplied bolts weren’t to correct length, but critical linkage all lined up nicely and it was easy to get things set where we wanted. The short levers give improved response over stock, and we think the Raasks look great on our bike.

A detail you can’t see is the new Shorai lithium battery housed under the tail of our bum-stop solo seat. We used Boxer Café’s new battery relocator kit to mount the battery, and we love how clean it looks with the battery moved from its nesting place behind the transmission. We know it’s hip to leave side covers off when you move the battery, but we think deleting them leaves a visual hole, and we like how the side covers tie the bodywork together.

Keeping to plan

We originally wanted a 2-into-1 custom exhaust system, but scheduling conflicts kept that from materializing. Instead, we sourced chrome header pipes from Mac Products and a pair of Dunstall-style mufflers from Dime City Cycles, and it turns out that might have been the way to go all along. The system looks great, and the mufflers tuck up perfectly, bolting to the stock mounts using simple aluminum brackets we made in the shop. And they sound glorious, more Moto Guzzi than BMW.

That same sort of serendipity presented itself with the front end, which we’d originally planned on kitting out with a factory dual-disc setup. We ended up keeping the /6’s stock single disc, which we sent to Spiegler Performance for their brake rotor conversion. That netted us a very nice drilled, semi-floating disc, and just like the exhaust, we think it looks  better than what we’d originally planned.

The fork brace was another bit of unplanned good fortune. The stock fender is mounted to a pressed-steel brace tying the forks together at the lower legs for support against twisting. You don’t want to run an R-bike without a brace, but the Boxer Café shorty café fender won’t fit the factory brace. The Phillips brace solved the issue, and it’s beautifully made. Combined with the café fender, black fork legs and Buchanan’s wheels, we think it really sets off the front of our Beemer.

A bit of work that did keep to plan was the incredible paint job by Travis at TC Concepts, conceived as homage to the smoked paint applied to the original café BMW of the Seventies, the R90S. Almost chocolate-colored depending on the light, Travis’ approach plays the black over the silver while still invoking a clear memory of the original. And if you think it looks good in photos, you should see it in the flesh. It’s stunning.

Race to rebuild: Coming together

Somehow, we always manage to delude ourselves that we’ll be able to zip through the bits that can require the most attention, and one bit we didn’t expect to take so long was the wiring, especially since we kept things fairly stock.

Simple things like re-wiring the taillight and turn signals — and our new Motogadget Motoscope Pro — ended up taking longer than we budgeted, reminding us once again that it’s the little things that really bite you when you’re trying to wrap up a big project like this.

But wrap it up we did, and it runs beautifully and sounds spectacular. Throttle response from the Mikunis is excellent, much crisper and quicker than the somewhat dull reply from the stock Bing units.

We didn’t touch the gearbox, but we were surprised how much better things felt in the shifting department, much of that no doubt down to the shorter throw from our new rearsets. The seating position has a decided café crouch, but once you settle in you discover there’s actually plenty of room to stretch out.

We put our Beemer on the dyno when we got it last year, and that first run netted 44.54hp at 6,500rpm and 41.51ft/lb of torque at 4,200rpm at the rear wheel, not particularly impressive measured against factory claimed specs of 60hp and 53ft/lb of torque at the crank. We made a second run with the finished bike, and the results weren’t notably different, with maximum power climbing to 47.55hp at 6,500rpm and torque at 42.42ft/lb. Dyno man Kent Clawson put sniffers in the tail pipes when he ran the bike both times, and on the second run he noted the bike was running decidedly rich. He thinks a bump or two down on main jet size would push horsepower close to 50.

That’s something new owner Bill Elliot, the winner of our BMW in the Race to Rebuild Sweepstakes drawing, will have to do. A rider and Motorcycle Classics subscriber, Bill was raised in a motorcycling family. His grandfather raced back in the day, and in the early 1960s founded Parmelee Honda in Fairfield, Conn., one of the very first Honda motorcycle dealerships in the state. In addition to a small collection of bikes, Bill’s active in the burgeoning café scene, with one of his current rides a café’d 1972 Honda CB750 he built himself. It’s a perfect happy ending.

So now it’s done, and we’re left feeling just a little lonely, the space occupied for so long by our custom BMW now bare. But that feeling won’t last long, because we’re already laying plans for the next Motorcycle Classics/Dairyland Cycle bike build. Stay tuned. MC