Ten Days with a 1973 BMW R75 /5

The Classic Experience
By Richard Backus
November/December 2009

1973 BMW R75 /5.
Photo by Landon Hall
Slideshow


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1973 BMW R75 /5
Recommended service

Oil change: Every three months or 2,000 miles
Air filter: Replace every 8,500 miles
Valve adjustment: Check/adjust every 8,500 miles
Spark plugs: Replace every 8,500 miles
Ignition points and timing: Replace points and adjust timing every 8,500 miles
Driveline splines: Clean and lube every 10,000 miles

Every time I ride a BMW R75 /5, it makes me wonder what I was thinking when I parted with mine a few years back. Sure, the Laverda that replaced it was a heck of a lot sexier, but there’s a price to pay for all that Italian flash, and it usually begins with a big “M” for maintenance.

While my 1983 Laverda RGS 1000 is actually quite reliable in its own Italian sort of way, there’s no escaping the extra level of attention it requires. Back in 1973, outside of maybe Honda with its superlative 4-stroke twins and fours, nobody made a machine as doggedly reliable as BMW, and the R75 /5 was the best machine BMW had going.

New flash for the new slash
Introduced in 1969, the 745cc R75 /5 was the biggest motorcycle in BMW’s new line of /5 models that also included the 498cc R50/5 and 599cc R60/5. Often considered more evolutionary than revolutionary, the new /5s were in fact a bit of both. While they retained BMW’s traditional boxer engine configuration (so named because the pistons of the horizontally opposed twin appear to “box” each other as the crankshaft spins) and shaft final drive, the /5s were significantly improved over their earlier brethren.

Where previous BMWs were kickstart only, the new /5 had Bosch electric starters (optional on the R50 /5). Breaker points and a pair of 6-volt coils replaced the previous magneto system, and charging was by a brushless alternator instead of the generator found in previous models. Better yet, the new alternator put out a whopping 180 watts, a 50 percent higher output than most other bikes then on the market.

Although purists were a bit uncertain about the revised Beemers, new comers to the Bavarian fold embraced the new bikes. Although not as fast as a contemporary Norton 850 Commando, the R75 /5 was faster than it looked, posting quarter-mile times in the high 13-second range and a top speed close to 110mph. It would tour effortlessly at 80mph all day long, returning 50mpg in the process, and it handled well, too, as capable on a two-lane back road as it was on the super slab. About the only thing you could really fault on the R75 /5 was the ho-hum performance of its dual drum brakes.

Riding the BMW R75 /5 today
If you’re new to the R75 /5 riding experience, you’re in for a treat. Unlike some bikes of their era, they require very little to get moving. Beyond the odd ignition key (it’s more of a nail with ridges than a key), starting an R75 /5 is fuss free. While the smaller bikes use slide-type Bing carburetors with “ticklers” for cold-starting, the R75 /5 has Bing constant-velocity carburetors. No fuel-fouled fingers on these bikes; just turn on the fuel taps, push down the choke lever on the left side of the engine and thumb the black starter button on the right handlebar, and the big twin spins to life; that’s assuming you have a healthy battery, as the huge Bosch starter will pull a less-than-charged battery down quickly.

Read Christian Fisher's experience owning and riding this 1973 BMW R75 /5

Most of our riding was in 80F temperatures, and while it took a few minutes to warm to a smooth idle, our bike would pull away cleanly after a half minute or so, choke off. Moving off is drama free, thanks to a relatively light clutch with a nice, linear feed. Our bike shifted quietly into first, an action typically accompanied by a loud “plonk” on most /5s, but the other three gears lived up to expectations, each shift requiring a firm lift on the lever that’s rewarded with a solid thunk of engagement.

It’s clear when shifting through the gears and getting up to speed that this is a bike that prefers a leisurely pace. The drive shaft exerts considerable effect on the suspension, the bike lifting with each burst of acceleration, then dropping down between shifts. Keeping the engine on boil and rushing the shifts helps a little, but the bike feels much happier if you let it work through its gyrations, gently rolling the throttle off and on as you work through each shift. It quickly becomes very familiar — and quite soothing.

That’s mostly thanks to the flat twin’s smooth power delivery, with ample torque from idle right on up to the bike’s indicated 6,800rpm redline. Peak torque comes at 5,000rpm, so there’s really not much point in running much over that, and frankly, the engine starts feeling strained as it nears 6,000rpm.

Not that we could really confirm exactly what sort of engine speeds we were running, as our test bike suffered from a common /5 malady of AWOL tach and speedo needles. Actually, they were right there in the combined tach/speedo instrument pod, just in pieces rattling around on the instrument face. Our bike’s odometer was also down, even though a quick check confirmed the speedo cable was intact and operating.

The R75 /5 really surprises at highway speeds. Two-lane or four, our bike had no trouble keeping up with traffic and in fact performed best at roughly 65 to 75mph. Smooth and stable, it felt more planted than my old R75 /5. That bike had the earlier short wheelbase, but starting in January 1973, BMW extended the rear swingarm by some 50mm to quiet down complaints of twitchy, unpredictable handling at high speeds.

The R75 /5 really shines on smaller two-lanes, where the bike’s predictable handling (aided in no small part by a brand new set of ContiGo! tires, Continental’s latest rubber for old bikes) and smooth power delivery make it a delight. Until you want to slow down, that is.

Although the early /5 drum brakes are generally regarded as perfectly adequate, the brakes on our test bike — particularly the front — had poor feel and were slow to grab. Most of the poor performance we experienced could probably be sorted with a thorough cleaning and readjustment of the brake system; worst case would be a new set of brake shoes.

We didn’t have a chance to run through the usual maintenance we conduct on Classic Experience test bikes (adjusting valves, replacing filters, etc. … see the BMW R90 /6 we previously tested), but we know from experience that for the do-it-yourselfer, /5s are among the easiest bikes out there to own. Everything is readily accessible, and an experienced DIYer can pull a /5 transmission to replace a clutch or leaky rear main seal (a common problem; new Viton seals last longer) in less than two hours. Plus, an ample supply of factory parts and a healthy aftermarket mean there’s basically nothing you can’t get for your /5.

Ten years ago, /5s were cheap. BMW made plenty, and their excellent build quality meant huge numbers of them stayed on the road. But prices are rising steadily as more people discover the joys of owning classic machines — and the ease of BMW ownership. For the person who really wants to ride their classic, a /5 is one of the best propositions out there, so if you think you want one, start looking now before they’re all gone. And if you have one already, don’t sell it. I can tell you from experience, you’ll wish you hadn’t.

Insider's view
Matt Richards
Boxerworks.com
Watkinsville, Ga.
(706) 310-0031
info@boxerworks.com 

Matt’s story: “I cut my teeth on 1955 and later BMWs when I worked for John Landstrom at Blue Moon Cycles in Norcross, Ga. I was working in the dealership when airheads were still being sold new on the floor. My first riding experience was a Kawasaki KE100 dirt bike in about 1979, but my first motorcycle was a 1978 BMW R100RS, and the first motorcycle job I got was BMW. Most guys evolve to the point of riding a Beemer, but instead of evolving into BMWs, I basically started with them.

“I was with Blue Moon for three years, then worked for another dealer and then at the Harley-Davidson tech facility. I’ve been doing Boxerworks.com for the last five years, which is now one of the biggest airhead-specific sites on the Internet.

“I like other bikes, and I have a pile of little Hondas. I just sold my R100R, and I’ve got an R69S project in the works, but believe it or not, I don’t have a full-blown touring bike right now. I’m dying for my old RS again!”

Why BMWs?: “I always tell people it doesn’t matter what brand you love the most, if you actually want to ride an old motorcycle, the /5 has to be considered the first modern sport touring bike ever made. An old /5 Beemer can’t be beat in that department. Out of all the bikes made in the 1970s, what’s the best bike ever made? Tell me the /5 isn’t in the top five?! For its age, you can’t buy a better motorcycle.”

Service recommendations: “Use good parts, don’t take short cuts, and don’t neglect stuff — that’s the oldest problem in the world, and the folly in the long run. The main thing is maintaining them as prescribed, that’s what gives these bikes their air of sheer durability. Lube the transmission input, driveshaft and final drive splines once a year or every 10,000 miles. Once you’ve done it a few times, it’s pretty straightforward. And keep the carbs properly balanced. When guys bust cranks (very rare) they’ve been running an extended time with their carbs out of balance. Basically, treat the bike as a system, focus on the whole machine and treat the bike as a living, breathing beast; overall health is more important than looking pretty.”

Watch out for: “Accessories. People always want to buy accessories, and they bolt crap on like fork braces and upgraded triple clamps. They want a fork brace before they’ve rebuilt the forks or the steering bearings. Trying to change the motorcycle is not the direction to go; you want to be a better rider.” MC 

Sample parts prices
www.boxerworks.com
Muffler: $350
Starter: $518 (OEM)/$350 (Nippon Denso conversion)
Air filter: $17
Front brake shoes: $67.81 (OEM)
Points/condenser: $35.50 set
Valve cover gasket set: $12 pair


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