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Christian Bynum's Classic BMW Motorcycles: 1976 R90/6
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Motorcycle Data Sheet

Model: 1976 BMW R90/6

Engine: 898cc 2-valve boxer twin (60 HP)

Years of Production: 1974-1976

Number Produced: 21,070

Purchase Date: December 2002

Previous Location: Seattle, WA

Previous Owners: 2

Mileage at Purchase: 71,000

Mileage to Date: 71,500

Restoration Projection: $5,700

Restoration Costs to Date: $3,700

Restor-o-meter: 65%


Background

I was lucky enough to buy this motorcycle from a really nice guy in my old neighborhood. Even though it wasn't quite running when I bought it in December 2002, everyone with whom I spoke advised me to go for it because the 90/6s were really great bikes.

Restoration

The motorcycle had not been cranked for the better part of a year, so the first thing I did was strip the bike down. I sold the unwanted Vetter fairing and Krauser cylinder guards, and I pulled the tattered bench seat and broken pannier racks off the frame. Because of the fairing removal, the motorcycle was missing some key parts to the turn signals and headlight bucket, which would require ordering. The front fender was cracked, so I tossed that too, reserving the hardware for resale. I also removed the tank and drained it of fouled gas, as I did for the carburetor float bowls. Then I changed the oil.

The bike sat, clean but dormant, under a tarp for the Christmas holiday, while my local mechanic, Mick Vallantine at R100/7 back into service on this bike.

I lucked out on piecing together the rest of the sheetmetal and fiberglass bodywork components from private individuals listing parts on the Internet, suggesting that with some diligence you can find decent parts without breaking the bank. My replacment dual seat (from a '79 R100RT), seat cowl (from a '78 R100RS), and gas tank (probably from from an '82 R100RT) were all purchased for under $80 each, well under the $650 I had originally budgeted for these items. The S-type (/7) front fender cost me another $40. Because of the cowl-type seat, I also wound up replacing the subframe with a /7 model, which has minor differences in the seat hinge post orientation from the stock /6. Of course, until I got the paintwork started, with its green, gold, brown, and black bodywork, this bike was pretty darn scary-looking! Still, the undignified look of its patchwork appearance during the early phase of its restoration will only serve to make the completion of the project that much sweeter...

With the help of my friend Howard, in May 2003 I installed short-shroud shocks and the /7 subframe, as well as alloy-body rear turn signals. (The front of the bike still lacked blinker stalks!) I also found a pair of oversize 898cc high-compression pistons (ratio = 9.5:1 as per the R90S engine) on eBay, for about half off the list price, which I boxed with my 33/11 final drive, awaiting future installation. My penultimate major coup in the process of parts acquisition was the double disc front fork and brakeset (i.e., everything but the rotors) in June 2003. With all the 90S bodywork save for the fairing shell awaiting paint renewal, I lacked only the quirky Dell'Orto carbs for my complete mechanical upgrade to 90S spec.

As spring 2003 transitioned into summer, I had my first real "catostrophic" maintenance issue on any of my Airhead bikes; with relatively little warning the transmission input shaft on this motorcycle gave up the ghost, apparently stripped, leaving the engine purring beautifully but transmitting nothing to the rear wheel in any gear. As a result, the bike was laid up for and largely neglected for the better part of a year! With some luck I was able to source a reliable replacement five-speed transmission from a 1978 /7 bike at a very reasonable price from a local enthusiast.

With other bike projects and more practical matters at hand, the drydock for the R90/6 that started as weekes and turned to months ended up being a full year, including a rainy winter parked (covered) outside on the street before I finally hauled it to my mechanic, Mick Vallantine, in August 2004 for major service, which included engine upgrades, a new front fork to cure the tracking problem, and dual front disc brakes, in addition to a new gearbox.

During the bike's time in drydock for the transmission trouble, I successfully sourced an NOS fibergalss replica S-style bikini fairing and an original R90S sports tank (with the correct raised gas cap). The tank wasn't as cost-effective as the lookalike /7 tank I had found at the start of the year, but as the scope of my restoration had grown from a cosmetic upgrade to a virtually complete match of the original 90S equipment, the proper tank bacame a more appropriate choice. I even found a pair of refurbished original R90S handlebar mounts in satin black with polished stripes at Joshua Buck's

The reconditioned high-compression engine bedded in nicely over the first few hundred miles post-rebuild, and shifting with the new gearbox is crisp and reliable. The new front end is stable and smooth, holding the bike's line incredibly well through sweeping turns. The dual disc brakes are a noticeable improvement, although the large-bore master cylinder might benefit from a rebuild for maximum stopping power.

In addition to installing the Dell'Orto carbs, the next item on the to-do list for this 900 is getting the S bodywork restored and painted in preparation for installation. Although I had been planing to restore the bodywork for this bike in one of the original R90/6 colors to avoid having anyone confuse my "cooked superbike" with the real thing, of late I have been lured by the siren's song of the 90S's fancy two-tone fades, Daytona Orange and Silver Smoke. I have decided on a Daytona Orange paint job by Charlie Moore, the skilled painter and owner of Tanks Only here in Seattle. I have seen his two-tone restoration work on a local R90S (below left), and it is fantastic.

custom bodywork for my developing cafe racer, which just returned from Tanks Only. I may also install the pair of Lester mag wheels I have, if I decide that the original equipment wheelset doesn't clean up to my satisfaction. New Metzeler tires are also in the offing.

In the end, I think this R90/6 will be a truly great bike, one of which I'll be very proud to have restored, to own, and to ride.

Maintenance

April 2003

  • Rebuilt headlamp (71K)
  • Changed engine oil (71K)
  • Flex-honed cylinder bores (71K)
  • Installed new sealed battery (71K)
May 2003
  • Upgraded subframe to /7 model (71K)
  • Shortened rear turn signal mounting bar to accommodate Krauser saddlebags (71K)
  • Installed alloy-body turn signals at rear (71K)
  • Installed short-shroud shock absorbers (71K)
  • Replaced fuses (71K)
August 2004
  • Replaced 5-speed transmission (71K)
  • Rebored cylinders to first oversize (71K)
  • Replaced piston rings(71K)
  • Renewed cylinder heads (71K)
  • Replaced front fork (71K)
  • Upgraded to dual-disc front brakes (71K)
  • Replaced front brake rotors and pads (71K)
  • Installed long front turn signal stem and brackets for S fairing (71K)
September 2004
  • Replaced carburetor float, valve, and gasket to stop leak (71K)
Acknowledgments

Thanks to the following individuals and companies for assisting in this restoration project: Howard Bialik, Barbara Bynum, Fred Inman, Peter Locke, Mike Mabie, Charlie Moore, DL Powers, Blake Richardson, Ride West BMW, Andrew Scudder, Bo Stewart, Chris Telford, and Mick Vallantine.

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