BMW /2 Hot Rod

Different people build different BMW conversions for different reasons. The BMW /2 was built to be a hot rod.
By Greg Williams
May/June 2014
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1965 BMW R60/2 Special
Photo by Sedrick Mitchell
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1965 BMW R60/2 Special
Claimed power: 67hp @ 7,000 rpm
Engine: 898cc air-cooled OHV horizontally opposed twin, 90mm x 70.6mm bore and stroke
Weight (wet/approx.): 450lb (204kg)
Fuel capacity/MPG: 6.5gal (24.6ltr) 

Depending on your perspective, it’s either sacrilege or the greatest idea ever. We’re talking about a vintage BMW “conversion.”

While there are many ways to go about something like this, this conversion begins with a stout and low-slung mid-Sixties BMW /2 chassis and adds a more modern and more powerful, but still classic, mid-Seventies BMW engine and transmission. This means classic looks and handling with increased power, 12-volt electrics instead of 6-volt, and five forward gears.

But first let’s share a little BMW model background. The /2 (Slash 2) chassis design first entered the scene in 1955, but it wasn’t until 1960 that the /2 designation was applied. Multiple models, including the R50/2, R60/2, and the R69S were built using the same basic chassis design, featuring either 494cc or 594cc engines in various states of tune.

What’s important about the /2 machines is the use of the Earles fork, a leading-link design developed by Ernest Earles and patented in 1953. The Earles fork doesn’t dive under braking and is stronger than a conventional telescopic design, with twin shock absorbers attached to a swingarm. Extremely rigid, the Earles fork made the BMW an ideal sidecar hauler.

The new breed

In 1970 BMW introduced a completely new line of machines, the 498cc R50/5, the 599cc R60/5 and the 745cc R75/5. These were the /5 Series of BMW motorcycles, and they incorporated a lighter yet much taller frame than their predecessors. They were also fitted with conventional telescopic front forks. Engines were much more refined and made more horsepower, and the old 6-volt generator and magneto system gave way to a 12-volt alternator and coil and breaker points ignition. Brakes, too, were improved.

But if you were dedicated to hauling around a sidecar, the chassis of the /5 wasn’t as ideal as the chassis of the /2. In the early 1970s, some bright spark thought to amalgamate the best of both worlds. “Back then,” says Pennsylvania-based BMW aficionado Brian Bailey, “a good used /2 was probably $600.”

Brian and his brothers have been around BMW motorcycles their entire lives. Brian’s first bike was an early Sixties single-cylinder BMW R27, and he then graduated to an R75/5. After blowing up the R75 engine, he modified this bike with an R90/6 engine. He still owns this motorcycle, along with his dad’s 1953 R51/3 and several others. “I helped my dad build a conversion in the early 1970s, and I also built one for my wife to ride,” Brian says.

Furthermore, Brian introduced his Harley-Davidson-riding neighbor, Mark McClymonds, to the BMW brand. Mark has a garage filled with half a dozen Harley-Davidson machines, from a vintage Panhead to a brand-new Project Rushmore-design Electra Glide Ultra Classic. He rides as often as he can, and takes extended motorcycle trips once a year — sometimes across the country.

The project starts

Mark was familiar with Brian’s BMWs, and the German-built motorcycles piqued his interest. Rather than simply buying one, however, Brian talked Mark into building a BMW conversion. With Brian’s help and connections within the vintage BMW crowd, Mark found a 1965 R60/2 rolling chassis. It had some front end damage, and the original Earles fork was slightly tweaked. What made it ideal for a conversion, though, was the fact the engine had at some point been parted out, and wasn’t included in the asking price. Mark bought the project in 2006 and began working on it in his garage.

For running gear, Brian suggested transplanting an early 1970s BMW R90S engine and transmission. Introduced in 1973, the R90S was BMW’s first Superbike. In fact, in 1976, Reg Pridmore won the first United States AMA Superbike Championship on an R90S. The 898cc powerplant with its 9.5:1 compression ratio gives Mark both kick and electric start, and a claimed 67 horsepower at 7,000rpm. “The kickstarter didn’t come on all of the early Seventies BMW models [it was deleted starting in 1975],” Brian says. “On a conversion, the kickstarter is the icing on the cake because it looks like an older /2, and it aesthetically ties it together.

“Through the years, many combinations of engines were mixed and matched to create the perfect machine for the intended task,” Brian says of BMW conversions. While a good many individuals built their machines with the sole intention of running them with a sidecar, other reasons did exist. The older /2 appealed to some riders as the increased seat height of the Seventies /5 bikes prevented riders with shorter inseams from being able to stand flat-footed over the bikes. Other conversions were simply built as hot rods, and that was Mark’s intention with this conversion.

To get started, Mark first ensured the frame on his /2 was straight. Fortunately, whatever damage the bike had incurred, the main frame rails weren’t out of line. Brian helped Mark source the R90S engine, and the pair closely inspected the running gear. With good compression readings and a new set of seals, the engine was given a clean bill of health. The older /2 engines have many of the same dimensions as /5 engines, but the newer R90S engine is taller and ever so slightly wider where it bolts into the bottom of the frame than the earlier units. To fit the engine, the lower frame rails had to be spread apart by approximately a quarter of an inch. In order for the newer /5 transmission and older /2 driveshaft to play nicely together, a spacer had to be machined to fit between the output shaft and the driveshaft.

If Mark had decided to straighten the original R60/2 Earles front end he would have had to further modify the fork for it to clear the R90S engine. At the back of the fork legs there is a stiffening loop just a few inches above the front swingarm pivot, and this loop would have to be flattened or cut out and repositioned higher up the fork legs to clear the front of the engine. Mark got around this by bolting in a smaller and lighter BMW R27 Earles fork, complete with fender and new taper roller bearings and shims. Brian helped Mark wire the BMW, using an R90S harness and converting all of the /2’s bulbs and horn to 12-volt pieces. A custom-fabricated bracket hides the R90S ignition coils under the gas tank. The headlight bucket is from an early BMW /5. This lamp assembly maintains the looks of the /2 model, but incorporates both a tachometer and a speedometer.

As a matter of routine, all the bearings and seals were replaced in both wheels and the rear drive, and new brake shoes were installed. All of the fasteners were replaced with stainless steel nuts and bolts. Many of the restoration parts, including bearings, seals, footpeg rubbers, the Denfeld solo saddle, the grips, the Hella bar end signals and the BMW “Euro” handlebars came from Craig Vechorik at Bench Mark Works LLC in Sturgis, Miss.

Mark runs a successful trucking business in Portersville, Pa. With some 450 trucks hauling out of his shop, he has a full complement of mechanics and auto body technicians on staff. That’s where the classic BMW black paint and white pinstripes were applied to the frame, fork, fenders and the 6.5-gallon tank. The crowning glory — as if the imposing R90S engine isn’t enough — is the handmade Epco stainless steel exhaust, including mufflers, which were produced in Germantown, Ohio.

Since completing the conversion in 2010, Mark figures he’s added some 1,000 miles to the BMW, and he says he got exactly what he wanted. “It handles like it is on rails, has terrific power, and it is just different and really neat.” Indeed.  MC


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Post a comment below.

 

TONYC
4/26/2014 9:06:22 AM
Nice conversion, but I would think that adding more power is only half the equation. What about upgrading the brakes (which were marginal even with the original engine).

Beargain
4/24/2014 5:57:18 PM
My brother had an R-60 that he bought, Like me, he was originally into Brit bikes. So the transition was difficult for me not him. You see my Brother was mechanically inept, he could ride and enjoyed wind in his hair but if he heard a sound that was odd. I would get a phone call and he would start with "I heard a noise" which would mean that I was going to his house on my Norton to fix his problem. The R-60 was a dependable fun to ride motorcycle but in my brothers hands it was a mystery. One time while getting ready to get on the Freeway I was in front and Mike was a bit behind. As I entered the turn lane I saw an oil slick and waved to Mike pointing to the oil slick. As I started up the onramp my girl friend tapped my shoulder and said that Mike had gone down. (the oil slick) I parked my Norton and walked back to find the BMW on its right head spinning around with Mike chasing it. When I got to the pair I pushed Mike out of the way and as the headlight came by I pulled the key. Got to replace the right valve cover. Great Bike when not in my Brothers hands. He finally went to a Goldwing but that as they say is another tale.








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