Ajays, the concept of laying an inline four cylinder engine on it's side for a motorcycle was an original BMW concept. To test the concept, BMW built a single proof of concept vehicle using an existing engine used in multiple French automobiles, called the Douvrin Suitcase engine. There are no known photos of this prototype. This engine was built in multiple sizes from 954 cc's to 1361 cc's. This engine was designed for use in small front drive cars and was therefore tilted forward 72 degrees from vertical and had the gearbox integrated into the sump with the gearbox running in engine oil.
Herr Fritzenwegger chose to use this engine, with the gear box removed and replaced with a standard BMW motorcycle gearbox behind the clutch, due to it's size, how close to horizontal it already was and the fact that the necessary mounting points were close to what they desired for a motorcycle. The engine was aluminum, but not an aluminum bore with Nikasil coating, it used detachable wet liners as Kawasaki did on the GPz 900 (and Harley does on my V-Rod), and it was single overhead cam design. It was also oversquare This is nothing like the engine architecture that turned up on our K bikes.
The only reason for that choice was to test the idea on a running prototype. It was conveniently close to the size and layout of what Herr Fritzenwegger wanted to build and allowed BMW to test the concept and work out the detailed layout they would need in their production engine. What we got was a pure BMW design, not a copy of a French engine. You are selling short the people and their imagination that brought us these bikes.

I don't have a source for the Sachs engine you mention. Keep in mind Chevrolet tried to build an aluminum block in line four in 1970 for the now infamous Vega. Fortunately for you, GM never tried to peddal that miserable POS in your market! Rather than use a bore coating like Nikasil, which was still many years in the future, cast in iron liners or steel wet sleeves like a big diesel engine, Chevy engineers chose to cast the engine from a high silicon aluminum alloy called 390 die-castable hypereutectic aluminum alloy thiniking this would create a suffiently hard wear surface for the pistons to run in, an idea of theirs that dated from 1950's research. It didn't work out that way. Cylinder wear was a major problem leading to premature failures of this engine, and is a major reason the Vega has such a miserable reputation.

Btw Ajays, my friend was one of the test riders at the Nardo test sessions. They acutally rode the disguised prototypes down to Nardo from Munich as a part of the test program, ran them at full throttle all day and all night during the tests, stopping them only for fuel and the barest of service, then rode them back to Munich.

FATH engine not Sachs......I can assure you he made a flat four engine somewhere in Scandinavia in his forest workshop from a block of aluminium. But I agree that it was not an inline four.
I therefore bow to your knowledge.
Ajays

[quote="Fath decided to go it alone, and with assistance from Dr Peter Kuhn of Heidelberg University and fellow racer/engineer Horst Owesle, the project took shape in Fath's forest workshop outside the town of Ursenbach, from which it took its name: URS. Although similar in outward appearance to the MV and Gilera fours, the eight-valve URS motor incorporated several unusual design features, not the least being its two separate crankshafts (set at 90 degrees) driving a common countershaft that had the contact-breakers for the twin-plug ignition mounted on its right-hand end. Kuhn's expertise and the use of special valve springs enabled the URS to rev at up to 15,000rpm, an exceptional figure for a 500cc four with two relatively large valves per cylinder. Bore and stroke dimensions of 60x44mm were chosen and Bosch fuel injection employed, the first successful use of such a system on a racing motorcycle. Although larger, heavier and possessing a higher centre of gravity than the rival BMW flat twin, the higher-revving URS four made 84-88bhp compared to the BMW's 65-70, which would prove more than enough to make up for those apparent handicaps. By July 1964 a prototype engine had been produced and later that same year made its track debut as a solo machine ridden by club racer, Paul Smetana. Unusually, Fath chose names rather than numbers for his engines, which were called 'Emil', 'Freidrich', 'Gustav' and 'Heinrich'. It is believed that only these four were built as complete engines, though parts were manufactured for several more. 'Gustav' was the most successful, usually being reserved for timed practice and the actual races. "][/quote]

You mean this bike:

http://www.bikeexif.com/motorcycle-sidecar-racing

The engine was a transverse in line DOHC four that looks fairly modern even today. It was also put in standard Rickman motorcycle frames and challenged MV Agusta in the 500 cc GP wars as a "Munch-URS"
It was not a flat four but a normal in line engine.

http://www.realclassic.co.uk/munch06090700.html

themason,
Thanks for that....I now know better than to query your statements in future but hasn't it been interesting.
Cheers Ajays

Our K with a VW Polo 3 cylinder diesel mounted.

Away from the subject of oil but thought you would be interested
Ajays

AJ I can't see photos you had posted!

Best regards,

Rafal,
Made good the picture...see above.
Ajays

Indeed I am! Diesel motorcycles interest me greatly and for a long time I have tried to chase down some info on a grainy photo of an Alaska Blau K-100RS looking bike that has a diesel. I don't know if this is the bike or not, but very interesting nonetheless.
I think I would probably scrape the crap out of that sump. I'd have to do something with less depth that tucks under the gear box a bit, but otherwise I bet that is a fun bike to ride. I would love to see BMW resurrect the original K-100 layout but as a direct injection turbo diesel. I'd buy one in a New York nanosecond.
Out here in the high desert we have Hayes Diversified Industries making a knock off of the KLR-650 A1 for the US Marines and British military with a proprietary single cylinder diesel engine that runs on JP-8. It has a lot of nice features taken from the KLR aftermarket such as the skid plate, foot pegs and jumbo fuel tank. It's a shame they have no excess capacity to make a civilian version. They had to expand their plant just to keep up with military orders.

http://www.hayes-dt.com/

Do you have more photos and information on this Polo engined K bike? It really interests me. Put a Paralever rear suspension and a Hossack front suspension on it, oh my!

themason,
This may be of interest..http://www.dieselbike.net/Hamm11/Hamm11.htm

Ajays

Our dear pibo has put a Smart diesel into his K...

I use 10W40 or a cheap 5W40 Oil. I never buy an use expensive Oil, because i change every year the motor Oil. Till today, i haven´t any Problems with that.

Some of us ride enough miles to require several oil changes each year, and ride in places with air temps in excess of 40 degrees C. I live in the vicinity of Death Valley. Sub freezing winters and extreme summer heat. Some days start off near freezing and end up a pleasant 19 or 20 degrees C in the afternoon. There are long desert roads where one can sit on the rev limiter in top gear for many minutes at a time. Oil quality matters.

''Motorcycle oil for wet clutches is very badly for the starter free-wheel.''

I ride a 1989 k75s and a 1983 good old airhead (R65). Unfortunately I ride them both only in the weekends and just for a few miles, therefore I change oil and filter every six months, as the mileage adds up ridiculously low for the last five years (kids in the family). I use motorcycle oil Valvoline durablend shemi-synthetic 20w-50 SG for the K and motorcycle oil Castrol multigrade 20w-50 SG for the R. Do I really cause damage to their engines according to the comment above, (which I've read earlier on the beginning of this thread), or I am just missing something?

Thank you for your patience,
Stavros

1989 K75s 125.000km
1983 R65 128.000km

Hello Stavros,


The main damage you are producing is the one to your bank account, I'd say. If your mileage doesn't add up to more than 7500 km in two years, you might begin thinking whether an additional oil change could be sensible. But to change oil every 6 months is - in my eyes - absolutely ridiculous. If you have money to burn, send it me - and I'll return at least some nice pictures to you!

My K75 never got anything else but the cheapest super market 15W40 (or for longer trips in hotter regions: 20W50), and as of today with 184 Mm on the odometer, never showed any sign of dissatisfaction with it.

Kind regards,

Peter

I agree 100%
I have yet to see any statistically relevant information that expensive oil is needed for our 30 year old engines.
I pay 2 € per liter for my oil and I don't see me buying anything else...

Do you remember the Essolube oil in bottles? You could buy the same oil at half the price unnamed.
Super markets have no refineries...it is top grade oil from major refineries....you pay high prices for name, marketing cost etc;
Get wise and save money.
Ajays

Thank you very much for your replies. I admit I do have a peculiar relationship with my motorcycles…

However in order to ‘’defend’’ myself and the frequent oil changes habit, I must say that both Clymer and Haynes manuals propose 6 months intervals, same goes for the official BMW maintenance schedule:

‘’Change oil when engine at regular operating temperature, renew oil filter element at least every 6 months; if motorcycle is used only for short journeys or at outside temperatures below 0°C, every 3 months, and at least every 3,000 km (1,800 miles)’’

Similar intervals are referred in the rider’s manuals too…

So I do understand I might exaggerate a bit the oil changes but what the heck…being for an hour in the garage listening to the radio and changing her fluids has definitely a soothing effect!

Thank you very much once more for your replies.

Stavros