/6 Questions

[godot]

Having owned only 80s airheads (w/dual discs brakes), I know almost nothing of the /6s.....but a few are for sale locally and I'm thinking of grabbing one while prices are down and the getting is good ($2k or so for a decent runner). I know there were some changes around '75 but not sure what they are, can anyone give me a quick rundown of the good, the bad, and the ugly of the /6 series. Any opinions, experience, things to look for other than the usual?

Pics of one local example, a '75 R75-

http://matthew.dev.deeplocal.com/bmw.zip

Btw, the above example is dual plugged. Why would someone do this to an R75? I thought that was an R100 thing.

Thanks.

[Major Softie]

Any opinions, experience, things to look for other than the usual?

Btw, the above example is dual plugged. Why would someone do this to an R75? I thought that was an R100 thing.

Thanks.

Some don't like the 14mm front axle. I think that is only the first year.

Actually, I think R60's are known to ping worst of all, and they have the highest CR at 9.2. All of that period benefit from dual plugging with our current gasoline. The R100 and the R75 have almost exactly the same CR (9.1 and 9.0 respectively). Yeah, the R100 has a little more distance for that flame front to travel, but they dropped the CR on the R100 to 8.2 in the 80's to deal with the change in gas.

[pkboxer]

Godot, I believe that with a '75, you would miss the major shortfalls.

'74 models had problems with shift dogs in the transmision. '74 also had the temptation of a kickstart, not on the '75 (at least not in the USA).

I think the flywheel bolts are larger on the '75 also.

'75 also got new switch gear, the drilled brake rotor, side to side ribs on the seat cover, plastic (not aluminum) turn signal housings.

You will probably have the same rocker arms as the '74 model, they were "upgraded" in '76 I think. Not a big deal though.

I think the transmision is the main reason people say to avoid the '74.

I think the front brake is the main weakness of the /6 vs. the later bikes.

[Kurt in S.A.]

Also, I believe the case spigot opening increased to 99mm with the '76 models. With that, you'd be able to drop onto it just about any cylinder from the later bikes. Without it, you have to modify the smaller opening or do something with the cylinder stub.

Kurt in S.A.

[Ken in Oklahoma]

What others have already said, plus:

I have a '76 R75/6 as well as later airheads.

If your 80's bike experience is only '81 and up, prepare to be disappointed with the /6 front braking, even with dual disks. The /6 bikes (with the exception of the R60) have ATE calipers with the under the tank master cylinder. '81 and up bikes will have dual brembo calipers up front (except at least some R65's). A lot of optimizing can be done to the older ATE setup including a second disk and caliper, but the Brembo setup is simply better. And when you get to the 88 monolever the front brakes become excellent (in airhead terms).

Also be prepared for a heavier clutch pull and more "flywheel effect" from the engine due to the heavier flywheel and clutch assembly when compared to the later "skeleton" clutch, or whatever it's called.

I prefer the /6 and /7 kickstands and don't like the '81 thru '87 kickstands. But I have a long inseam which actually makes deployment from the saddle possible.

Also be prepared for what will feel like a goofy turn signal switch on the R/H brake perch. It will feel all wrong, including which way you push the lever for left and right.

The powerband will feel a bit different from the late 80's bike, less torquey. Plus if you're used to R100 then the R75/6 and even the R90/6 will feel a bit down on power.

You will also be pleased with a lot about the /6 bikes. Simply, they look a bit more "vintage" with their "slab sided" fuel tanks, longer front fender with lower fender brace, and older style valve covers. And then there is the clam shell air filter housing which looks "just right" on an airhead. Plus you won't have those vertical fins on the timing chain "chest".

If you buy a /6 I predict that you will thoroughly enjoy it.


Ken

Having said all that you will feel pretty much at home on the /6 bike.

[Max Headroom]

As already stated, there are minor (and a few major) variations between each model year. Switchgear, brakes, starter motor, fasteners, flywheel, gearbox, rocker shafts, barrels, pushrods, pushrod tubes, front axle, wiring loom, these are some of the detail changes just within the /6 range. Thirty-six years on, I doubt there would be many '74 models running around with the original gearbox still untouched, so that shouldn't be a deal-breaker any more. Although the /6 was a development of the /5 and used its basic architecture, the /6 was effectively the first of the "modern" airhead range with its instrument binnacle design, the R90S fuel tank and seat cowl styling, 5-speed 'box, etc.

Broadly, the '76 models got the benefit of three years of ongoing development, along with some pre-cursors for the /7 series. There aren't any real lemons in the range, and due to the interchangeability of the airheads, you can alter, upgrade or tweak anything that doesn't quite suit you.

I'm a fan of the /6 range (in case you hadn't guessed!), and can recommend them if you're looking for a practical classic which can still provide reliable travel. I'd personally suggest a '76 in order to benefit from the factory upgrades, but buy on condition and history first and worry less about the year of manufacture.

[mattcfish]

Some 75 bikes have some of the 76 improvements some don't. My R90/6 built in Sept of 1975 has the larger 11mm flywheel bolts. Some 75 and most if not all 74 bikes used 10mm bolts. I also have the smaller pushrod tubes and the smaller cylinder spigots (97mm vs 99mm). So if I want to go to Nikosil or just to 100cc pistons I will need to modify the block. pre-76 bikes use a small seal on the camshaft. The rockers need a little more attention to alignment. Some of the wiring varies between 75 and 76, especially concerning the starter relay. I've had mine for over 20 years. With the addition of dual brakes, Dellorto carbs and some other modifications, it eats later airheads for lunch. I love this bike.

[Max Headroom]

Yeah, many of the changes were "running" changes which weren't specific to a model year as such, they were simply introduced as stock ran out. Apparently some of the last R90S bikes were delivered with the flush /7 fuelcaps, as an example. The 11mm flywheel bolts were introduced sometime in 1975, 'cos my Feb '75 R90/6 had them.

[godot]

Thanks for the replies. Great info.

I lived w/dual ATEs on my old R100 and I really, really like my double Brembos on the lighter, nimbler LS. I should probably just factor the cost of upgrading to dual ATEs into any /6 I consider.

[SteveD]

Thanks for the replies. Great info.

I lived w/dual ATEs on my old R100 and I really, really like my double Brembos on the lighter, nimbler LS. I should probably just factor the cost of upgrading to dual ATEs into any /6 I consider.

Are they ate's or brembos on the LS? The earlier ones had ate's that looked like the brembo's, and behaved like them too luckily enough!