The R65 does not have the type 247 engine?

[Steve]

Wikipedia under the entry "BMW 247 engine" says that it was airhead engines from 1969 to 1995 but that the R45 and R65 (though made during those years) have the Type 248/1 engine.
1) Do these numbers have any meaning as far as BMW is concerned?
2) Are the R45 and R65 engines really so different?
3) If the type 248 engine is a real thing, were the designers attempting an improvement? What were they trying to improve?
4) Were there any type 248s other than on the R45s and R65s?
(I never even heard of this 247 designation until recently.)

[georgesgiralt]

Hello,
R45 and R65 engine share a lot of characteristics from their bigger mates but one is very very different. The engine has 61.5 mm travel.... This make for different jugs, and casing (as the tubes for the pus rods are at a different angle due to shorten barrels... So yes, a new engine type. Even if it looks familiar...

[dogshome]

You can swap the whole lump out 247 to 248 and vice versa though.

Other changes to the rest of the bike are front triple tree and forks, battery, swing arm and subframe length. Also seat is shorter and front wheel is smaller. Some changes to rim size, final drive ratio (that can also be swapped as a unit). Various other things like clocks, master cylinder etc with differences.

[Barry]

Wikipedia under the entry "BMW 247 engine" says that it was airhead engines from 1969 to 1995 but that the R45 and R65 (though made during those years) have the Type 248/1 engine.
1) Do these numbers have any meaning as far as BMW is concerned?
2) Are the R45 and R65 engines really so different?
3) If the type 248 engine is a real thing, were the designers attempting an improvement? What were they trying to improve?
4) Were there any type 248s other than on the R45s and R65s?
(I never even heard of this 247 designation until recently.)

1.  Wikipedia is correct.  BMW introduced the R45/65 engines as type 248.   These designations are reasonably well known on airhead
     forums
2.  Besides the shorter stroke and despite the fact that the engine has the same overall dimensions as the type 247, there
     are some other differences such as the engine breather and oil drain back to sump. The crankcases castings are not the same.
3.  I wouldn't have called it an improvement but who knows what BMW had in mind.  In terms of capacity the type 247 500c R50 had
     already been discontinued and the 600c R60/7 was discontinued very shortly after the introduction of the R65 so I presume the
     new models were designed to fill that gap in the range. The real question is why a shorter stroke.  BMW were moving away from
     heavy flywheel engines and probably considered the shorter stroke more modern and it also gave better cornering clearance.
     Another speculation is that BMW might have already been considering scrapping the 247's in favour of the K series bikes and
     might have intended to retain the R45/65's as basic models. 
4. No

[Steve]

A mechanic that worked on my bike once grumbled, "Why did they make the R65 so different? Because they could, I guess." I think he meant that, as far as he was concerned, any minor benefits of the R65 over the previous models weren't worth the added complication in terms of different parts and service requirements. But being rather small I appreciate the smaller sub-frame and so forth. I'd say some of the changes were worthwhile for those who don't need the biggest bike available. Other changes, like the shorter stroke, I don't know enough to judge.

[Burt]

When I purchased mine it was also an entry level BMW as it was the smallest capacity engine available and the cheapest.  Other options at the time were either the various R80 or R100s, as well as the R65LS.  The K series had just arrived but were a bit of an unknown and suggesting to an airhead owner they they upgrade to a K bike was akin to swearing in polite company. 

[Barry]

Some aspects of the R45/65 lead the way, for example the basic front fork internal design was soon adopted  by the type 247 airheads. Even still many parts are not inter changeable. I don't think anyone would claim the new design was better than the old and probably the main distinguishing feature being it was cheaper to manufacture. 

Other aspects of leading the way which I consider a definite improvement were:

Locating the front brake master cylinder on the handlebars instead of under the tank

Introducing a proper dual piston brake caliper instead of the odd pivoted design that was harder to set up.

Moving the spaghetti junction of wiring inside the headlamp shell and fuses to under the tank and behind the side panel.

[georgesgiralt]

As far as I know and heard when I was younger, was that the R45 and R65 were the new design set to replace their bigger sisters. Shorter wheel base and faster revving engine and revised everywhere.
Alas, it seems that the public did not buy them at that time, that the design of the 1981 model (which was meant to be in the 1978 R45 & R65 was postponed because the development of the K line ate all the budget and manpower. So they offered bikes with poor power and stamina to users willing to have large fairings and high torque engines.
BMW missed that point and the K line engineers and marketing people almost killed the R line entirely stating that the "new design" was a failure so it was impossible for BMW to meet the Japanese bike performance with R style bikes, hence BMW should only sell the true Japanese competitor : the K line....
The R65 I bought new in 1984 had sat at the dealer for two years. HE had an 1981 and another 1982 R65 plus 4 R45 sitting in the shop.... HE was glad I bough one. At that time the saying was that they sold like two seats coffins...
At this time, in Europe, BMW sold a set of RT fairings adapted to the R65 in order to clear the R65 stock. And I do not speak about the LS which was considered ugly by the crowd....
These bikes could have been a success if the BMW customer base had not been so conservative and judged them for what they where. Very nice bikes with very good performance and economy of use...

[Steve]

George, you left out an end parenthesis. Did you mean to say that the 1979 R45s & R65s were supposed to have all the features that ended up in the 1981 model (like lighter flywheel and Halls effect ignition) but they were postponed due to development of the K line?

By the way, there is a web site called theparking-motorcycle.com that has 209 R65s for sale, all in Germany. The year models get as high as the mid-90s. Its popularity over there should be favorable in terms of getting parts as the years go buy.

[georgesgiralt]

Yes Steve, this is what I was told. I do not pretend it is factory information, but things I was told one day (when the K line went out, BMW organized bike trials at the various dealers with a large range of bikes. They were supervised by a bunch of BMW corporate people, most of them for taking orders... and one more "senior" or marketing. He was him who told me that seeing I used an R65 and what I wrote above is my recollection of this.) I was, and I still am surprised because it make no industrial sense to postpone an engineering mod for which you have spent a lot of money and engineering manpower.  And I though strange that the new models, if engineered to use the "new engines" had to be engineered "backward" for production... But, you know...
At that time, as an engineer, I was astonished by the K bikes, but as I was dead broke, I preferred to discuss with the BMW guys instead of riding the unaffordable bikes...

[Barry]

I think it's generally accepted that BMW did originally intend to replace the airheads with the K bikes but were forced by customer response to change tack and develop the flat twins in parallel. I remember the K bikes coming out and a friend had a one. I didn't much like it, fast yes but not all of them were as smooth as a good flat twin. My abiding memory of it was the primary drive gear whine which was vey Japanese in character. Traditional BMW customers wouldn't have liked that.

I'm surprised BMW delayed development of early model R45/R65 as it's not as if they were able to use any existing type 247 parts.  The heavy flywheel and clutch for example on the 78-80 R45/R65 is not the same as the contemporary type 247's, it's smaller in diameter.

[Steve]

To me it's odd that, though it was a new engine, it looked the same. Any of the contemporary larger engines, alongside, look the same. Like they had a design language they wanted to stick with for appearance sake. Were the designers conservative aesthetically or did they think their customers would prefer the standard engine look.