FROM /5 TO /6
Bob Hardacker seems more interested in living life than talking about it. Not to say that the 60-something engineer is anything other than warm and friendly, but his skill of getting to the point makes every conversation useful.
‘People often ask: why BMW?’, Bob says candidly. ‘There could be a hundred reasons. Who has time for that?’
California racer Billy Ross introduced me to Bob when he learned I was searching for information on the /6 series which followed the /5 from 1973. There’s modern Beemers hiding in Bob’s workshop, but at heart he is hardcore vintage.
‘My concerns are more related to performance than reliability,’ Bob answered when asked about the /5’s possible warts. ‘Each new series was bigger and faster, but not necessarily better. That’s subjective.’ So is explained Hardacker’s admiration for the 1974-76 range, and especially his carefully done R90/6. ‘It’s slim and light like before but with a bigger engine,’ Bob grins. I’ve been promised a ride on his blueprinted red rocket, and next trip out I’m taking it. Stay tuned.
‘In my opinion, the /5’s smaller diameter front axle and rocker arm bushings
(vs needle bearings) were important upgrades to the slash-six. But these were improvements, not fixes,’ Bob says, deliberately making the point. ‘These things can be added on later. Properly adjusted, the /5’s 200mm drum is actually better than the single 38mm disc on the early /6. Changing to a larger 25AH battery and 280W alternator improved starting, but the R75 kickstarter (and mainstand) is heavier as they were designed to be used. Being opinionated I prefer the fivespeed. Those four-speeds on the /5s are classic clunkers – solid, but not quick shifting. Proper shimming at rebuild is a must. Again, I prefer the /6 clocks and switches, plus the headlight is bigger and brighter.
‘From a reliability standpoint the /5s are pretty bulletproof. There’s a lot of the “old works” in those machines and lots of extensive hand work. That was a big advantage to the four-cylinder K-bikes; far cheaper to build. One example of this are the /5’s screw terminals for wiring vs ¼” push-ons. Those terminals make for excellent contact, and while the push-on connectors are convenient, they tend to loosen over time.
‘A strong point about this vintage of BMW is how incremental the improvements were. Dedicated for sure, but cost was always a factor. Given the longevity, I’d say BMW delivered on its promise of building a superior bike.’