Race to Rebuild: The BMW R90/6 Part 4

The Motorcycle Classics/Dairyland Cycle Race to Rebuild 1974 BMW R90/6 is racing to a finish, and it’s looking like a winner.

| March/April 2013

  • race
    Like every build we’ve done, our 1974 BMW R90/6 has seen more then a few twists and turns in the road to completion.
    Photo Courtesy MC Staff
  • 1974 BMW
    We’ve ditched the stock clocks in favor of a Motogadget Motoscope Pro. It’s minimalist and very cool.
    Photo Courtesy MC Staff
  • Rebuild
    New 32mm Mikunis replace the original Bing units.
    Photo Courtesy MC Staff
  • Diode
    A new diode/rectifier board replaces the original unit, which was failing.
    Photo Courtesy MC Staff
  • replaced wheels
    Relaced wheels from Buchanan’s are fabulous.
    Photo Courtesy MC Staff
  • castings
    The BMW’s castings are decidedly porous, a fact brought to light during cleaning, which was a real challenge.
    Photo Courtesy MC Staff
  • 1974 BMW shocks
    Gazi Sport X shocks look perfect, a huge improvement over stock units.
    Photo Courtesy MC Staff
  • Engine cover
    The engine cover will be black like our new valve covers.
    Photo Courtesy MC Staff
  • BMW seat
    Lovely seat from Tom’s.
    Photo Courtesy MC Staff

  • race
  • 1974 BMW
  • Rebuild
  • Diode
  • replaced wheels
  • castings
  • 1974 BMW shocks
  • Engine cover
  • BMW seat

If you’re disappointed not seeing the finished Motorcycle Classics/Dairyland Cycle Race to Rebuild BMW, don’t be. We could show you more, but then we wouldn’t be able to tell you more about our race to the finish, and we wouldn’t be able to show you the finished bike with, we hope, its new owner.

OK, so maybe we like stringing things out a bit. But in this case we have a good reason, namely the simple fact that as of press time, the winner of the Motorcycle Classics/Dairyland Cycle Race to Rebuild Sweepstakes hadn’t been confirmed. Because of that, we decided it’d be more fun to wait until next issue to unveil our finished BMW and let everyone, the winner and the rest of you, experience the finale at the same time.

Like every build we’ve done, our 1974 BMW R90/6 has seen more then a few twists and turns in the road to completion. Last issue, we told you about some of the unexpected mechanical issues we had to sort through (cylinder head woes, instrument woes, etc.). Since then, we had a few more head-scratchers, most notably figuring out how to mount the très cool replica Ducati 900SS fairing we got from Airtech.

Following an established practice of “ready, fire, aim,” we settled on the fairing we wanted before researching how to attach it. When we discovered there are no kits to mount Ducati fairings on BMWs, we just dove in deeper. If you’re a commercial fabricator, mounting a fairing is just another challenge in metal, cutting and welding your way. But we’re not commercial fabricators, and while we keep swearing we’re going to learn to weld, neither of us has. So we did what we always do, and that was spend a little extra time — time we didn’t really have — figuring out a way to mount our Ducati fairing. Eventually we did figure it out, and next issue we’ll show you what we came up with.

Another issue was instrumentation. Originally, we liked the idea of keeping the stock clocks on our Beemer, but eventually we decided the cost of overhaul just didn’t make sense. Used units are expensive — if they work — and a speedo/tach rebuild can run from $350 to as much as $1,000. Enter Spiegler Performance Parts, who sell an amazing array of digital instruments including the super hip Motogadget Motoscope Pro. For about the same money as a rebuild ($547 with the mounting plate) we got a new digital speedo/tach that’s easy to configure, plus it is set up to accept optional “breakout” boxes to let you input just about anything you could possibly want to through the Motoscope Pro. And by way of major bonus, it looks fantastic on our custom R90.

We also had Spiegler perform their BMW brake rotor conversion. We didn’t strictly need a new rotor, but we were intrigued by Spiegler’s conversion, which involves removing the stock rotor from its carrier and mounting a new stainless steel rotor on buttons for a semi-floating disc brake. It should work excellently and it’s also cost-effective, as a stock replacement rotor from BMW runs $350 and the Spiegler conversion is $240. Very cool.

We also discovered that the original diode/rectifier assembly and its associated wiring was burning up, so we turned to Euro Motoelectrics for a replacement and a new, adjustable voltage regulator. The new diode/rectifier came complete with new alternator brushes, and the adjustable regulator lets you tailor voltage output, useful if you do a lot of low rpm urban cruising.

The good stuff keeps coming

Our Beemer’s suspension went together beautifully, aided in no small part by Matt Wiley at Moto-Services.net, who performed a custom install of our Race Tech Gold Valve Cartridge Emulators. We’ve installed these on two bikes previously (a BMW R60/6 and editor Backus’ Laverda) and the difference in performance over stock has to be experienced, as they enable the front forks to glide smoothly over large bumps that would previously knock your fillings out. We also installed our new Gazi Sport X shocks from Flatland Custom Cycles. Beautifully made units, they’re a simple bolt-on installation.

Moto-Services also handled our hydraulic work, rebuilding the R90’s brake master cylinder and front brake rotor. We’d originally planned on installing an R90S dual-disc setup, but as we got deeper into the project we decided to stick with the stock single-disc setup. That was partly because the dual-disc requires a different master cylinder. The stock BMW unit runs about $400, but if you decide to go aftermarket to save some money your only choice is a handlebar-mounted master cylinder. That means ditching the stock switchgear, something we really didn’t want to do. We like how the stock units look and function, so with the addition of a new set of 2.25-inch-rise Flanders bars from Bob’s BMW the stock setup stayed put.

To ensure the bugs stay out of our faces we turned to Gustafsson Plastics for a dark-smoked windscreen. It looks predictably excellent, and the fit on our Airtech fairing is pretty much perfect. If you’ve never checked them out, Gustafsson has windscreens for a huge variety of vintage and modern bikes, including screens for all of the Airtech fairings, Boxerworks fairings, Vetter fairings and more.

Rolling, rolling …

We had Kennie and crew at Buchanan’s Spoke & Rim build our wheels with black anodized Sun rims set off with stainless steel spokes, and the visual result is amazing. Laced up to stock hubs powder-coated satin black and freshly shod with Kenda K657 Challenger tires, the wheels have the tailored look we were going for.

Of course the single biggest visual on any bike is the paint, which was applied to our Beemer by maestro Travis Charbonneau at TC Concepts. Travis did the paintwork on our Triumph Bonneville custom, giving that bike a gold and black paint scheme that harkened back to Triumphs of the mid-1960s. Our aim this time was BMWs of the mid-1970s, more pointedly the iconic R90S, and Travis’ work doesn’t disappoint. You’ll have to wait till next issue to see Travis’ results, but the R90S-esque paint scheme combined with satin black fork legs and wheel hubs, gloss black valve covers and front engine cover, top engine cover and frame — and plenty of polished aluminum — make this Beemer a stand out.

Stay tuned until next issue, when we finally pull the wraps off the Motorcycle Classics/Dairyland Cycle Race to Rebuild BMW R90/6. And if you just can’t wait till next issue, check for updates on Dairyland Cycle’s Race to Rebuild Facebook page, where we’ll first announce the winner of our Race to Rebuild Sweepstakes. MC 

For more information 

Race to Rebuild Part 1: The adventure to fix up a 1974 R90/6 begins.
Race to Rebuild Part 2: After deconstructive surgery, the transformation of our 1974 BMW R90/6 starts.
Race to Rebuild Part 3: Our project 1974 BMW R90/6 may be in pieces, but we're quickly getting traction on our build.

Race to Rebuild suppliers

Airtech: Fiberglass replica Ducati fairing
All Balls Racing: Steering, wheel and swingarm bearing kits
Bob’s BMW: Factory BMW replacement parts, Flanders handlebars, parts and technical assistance
Boxer Café: Fiberglass starter cover, café tail section and seat pan, battery relocating kit
Buchanan’s Spoke & Rim: Custom wheel build with black anodized Sun aluminum rims and stainless steel spokes
Custom Coatings & Metal: Media stripping and custom powder coating
EBC: Brake pads
Euro Motoelectrics: Alternator diode board, diode board wiring harness, adjustable voltage regulator
Flatland Custom Cycles: Gazi Sport X shock absorbers
Gustafsson Plastics: Smoked windscreen and hardware for Airtech fairing
Joker Machine: Custom mirrors and turn signals
K&N Filters: Air and oil filters
Kenda Tires: Challenger K657 tires
Mac Products: Complete replacement exhaust system
Moto-Services.net: Race Tech Gold Valve Emulator front fork conversion, hydraulic master cylinder and brake caliper overhaul
Omar’s Rearsets: Raask rearsets
Race Tech: Front fork springs and Gold Valve Cartridge Emulators
Rocky Point Cycle: Dual 32mm Mikuni carburetor kit
Shorai: Lithium iron battery
Spiegler Performance Parts: Braided stainless steel brake line, Motogadget digital instrument cluster, brake rotor conversion
TC Concepts: Custom painting
Tom’s Upholstery: Topeka, Kan. (785) 235-2061

gerald estes III
3/2/2013 1:37:35 AM

project beemer - wow. keepers of the faith, thnx. project beemer image gallery: finally, a "naked bike" worth some consideration. for the most part im in agreement w/ the upgrade replacement parts. id complete the chassis a bit differently - a leather covered piece of plywood? if it was mine to ride...looking ridgid aint very plush and would probably add up to zilch windshield time on my part - suggestion? stick with your projected goal and budget for it.

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