I dont know what this is but I like it

"sony1492" (sony1492) 09/29/2019 at 17:06 • Filed to: Moar crankcase

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10

It has a bmw badge, that's about it

beardsbynelly - Rikerbeard > sony1492 09/29/2019 at 17:53

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BMW R of some sorts. I think an R65

My X-type is too a real Jaguar > beardsbynelly - Rikerbeard 09/29/2019 at 18:21

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Looks like a 75 I think

https://www.ebay.com/itm/1970-BMW-R-Series/163875439996?hash=item2627bcc57c:g:f8IAAOSwaF5diAKj

BoxerFanatic, troublesome iconoclast. > sony1492 09/29/2019 at 18:59

5

This is a BMW R-bike, probably a /5, but the actual name d epends on it’s displacement, which should be listed on the badge above the cylinder. The large tank was an option, but more likely standard on the higher displacement engines for longer distance riding. The smaller 500cc bikes usually had a smaller tank than this, with an optional chrome side panel, which are referred to as the “toaster tank” option.

With telescopic forks, and drum brakes, it is probably an Rxx/5. R50/5 is 500cc, R65 would be 650cc, R75/5 is 750ccs. Later versions of the /6 and /7 went to 90 (900ccs) or 100 (1 liter, 1000ccs), and added things like disc brakes, and cast wheels, and eventually the first paralever rear suspension geometry.

Earlier bikes before the /5 series had an earle’s fork design that incorporated a steerable swingarm, and a coil-over shock. /5, /6, and /7 series had telescopic forks, before going to telelever in the 90s, with the oil-head bikes (slang for 4-valve BMW boxer bikes with engine oil supplementing the air-cooled cylinder heads)

This is commonly called an air-head. air-cooled cylinder boxer engine, flat-twin. Similar arrangement to VW and Porsche cars, but with fewer cylinders.

Air heads have rounded valve covers that look like a peanut shell, which this bike has. Later ‘80s air-heads had flatter valve covers with raised horizontal lines.

Later came oil-heads, with 4-valves per cylinder, and oil-assisted cooling, the cylinder heads looked like rounded-off rectangles, with a plug lead cover across the side. This is a re-designed engine, compared to the earlier air-head engines, and are designed to be stressed-members, with the engine case strong enough to be a part of the chassis/frame of the bike . Generally 1100-1150ccs, except for the 1200C cruiser that was a modified oil-head.

hex-heads have newer 4-valve pushrod heads with 2 valves per cylinder, valve covers with six sides, an update over the oil-head, these are usually 1200cc engines. (some other markets had rarer 800-850cc versions of these before the BMW F-series parallel twin bikes came out as the entry level line)

Cam-heads look similar to hex-heads, but are generally 1200-1250 cc from the mid-2000s into the 2010s.

More recently the air-oil overhead cam engines have been superceded by the newest “Wasserboxer” engines, 1250ccs and water-cooled. Still a flat twin boxer, but a completely new engine design.

sony1492 > BoxerFanatic, troublesome iconoclast. 09/29/2019 at 19:32

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Thank you for the info

This had the rear coilover so it must be a 5, what’s up with the intake integrated with the block?

arl > sony1492 09/29/2019 at 21:07

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My extremely short span of motorcycle driving includes putting around a parking lot on an old R90. Neat old bikes.

BoxerFanatic, troublesome iconoclast. > sony1492 09/29/2019 at 21:45

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That is actually the airbox cover. There should be a panel line between the airbox lid at the back of the engine block , with the gearbox below. It is designed to look integral. The ignition, and starter are in the top of the block under the fuel tank. The cam is under the crankshaft, and the generator/alternator is on the front of the crankshaft.

in this image, the airbox is at the back top, behind the starter.

beardsbynelly - Rikerbeard > My X-type is too a real Jaguar 09/30/2019 at 07:49

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really can’t tell from the picture what displacement it has . Boxerfanatic has a good reply above that goes into more detail.

bob and john > BoxerFanatic, troublesome iconoclast. 10/02/2019 at 22:19

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you uhh....you live up to your name there bud


I like it. we should be friends.

BoxerFanatic, troublesome iconoclast. > bob and john 10/02/2019 at 22:45

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Glad to accept that sort of invitation, but I do sometimes live up to the description, too. ;-)

McMike > BoxerFanatic, troublesome iconoclast. 10/05/2019 at 14:18

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Username checks out.