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stephan.pretorius
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Derry, NH
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When I came to the US 17years ago, I met a man who told me about his old BMW. At the time I was lead to believe that it was an early 60's R50 model. Recently I became the owner of this motorcycle. It was difficult to pin the model/year on this one as it appears to be a healthy conglomerate of different models. Thanks to this site I was able to identify the motorcycle accurately (frame and engine numbers): it turns out to be a 1951 R51/3. The motorcycle is not running and is in desperate need of some TLC.

The motorcycle has a long seat (2passenger?) and also a baggage porter (72609034144). It is fitted with chromed fenders and the mufflers don't look like anything I have seen on recent pictures. The handle bars have quite an aggressive "drop" to them as well.

Is there any record out there of these motorcycles being built with chromed fenders?

With thanks,
Stephan

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New Hampshire, USA
Darryl.Richman
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Welcome to the forum! Chromed

Welcome to the forum!

Chromed fenders? Not that I know of. That's not to say that BMW didn't do it; generally, BMW would paint or accessorize bikes to accommodate a purchaser, if they were buying enough bikes. The story about the three colors that Butler & Smith ordered up in the late 60s on some US bikes follow this theme. But to document it as being correct from the factory, you'd have to find out who put in the order and when, and then establish a link between your bike and that order.

Generally, differences from the norm such as you describe are the work of the owners of the bike. My R51/3 and my R60/2 both have chromed air cleaners because previous owners of both bikes decided they liked a bit more sparkle on the bike. You also often see the parts of the motor that are easiest to remove, that have been polished to a shine. I think that looks weird, but it seems to make some people happy, and hey, it's not my bike.

During the 80s and 90s there weren't a lot of parts around for these bikes, and the original mufflers had a strong tendency to rust out from the inside, so you often see these bikes with non-stock mufflers that have been adapted. And handlebars are easy to change, especially on bikes that don't have hydraulic lines.

The upside to this is that many of these parts are available again. The ones that BMW supplies fit as originals, in my experience, and look original. So, as time and money allows, you can make the bike look more and more original (if that is your goal). But it would be best to start first by making it run correctly first.

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schrader7032
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Welcome, Stephan. I don't

Welcome, Stephan. I don't have any specific knowledge about the R51s. You might get some info from BMW directly. Email Andreas Harz at "Andreas (dot) Harz (at) partner (dot) bmwgroup (dot) com" and provide info about your bike and see what they might say about how it left the factory.

I doubt they had chrome fenders. In looking at Ian Falloon's book on the boxers from '50 to '96, there are some pictures of the early '50s bikes and none have chrome fenders...they're all painted black. Some of the bracing might have been chromed.

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'78 R100/7 '69 R69S '52 R25/2

jeff dean
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R51/3

This might be helpful:

http://bmwdean.com/r51.htm

They are beautiful bikes!

stephan.pretorius
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Derry, NH
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1951 BMW R51/3

Thank you for the feedback. Looking at what the fenders should look like, the ones on my motorcycle are quite different: they do not even look remotely close to what the pictures show...So I only found out yesterday prior to my first posting what the model was and I have to admit I am quite eager to get started on this project.

I will take pictures and post before I do anything.

Up in my neck of the woods I found out that my local BMW store (I also own a K1200RS) lists the parts fiche online, which I use to help with the identification of the parts: http://www.maxbmwmotorcycles.com/fiche/DiagramsMain.aspx?vid=48035&rnd=0...

Parts that are chromed include the front and rear mudguards (both not original), as well as both bulb supports (original). Other non-originals include the seat and the tank.

I found what I think is the battery cover (bakelite): the fiche shows it as a battery, but I only have the top part. The main stand is gone, but there is a side stand coming out from the left footrest - does not seem original...Any thoughts?

As far as the engine goes: I received the motorcycle with both tops (heads) removed. The previous owner had removed them many years ago due to an oil leak he tried to fix and never got to putting them back. I have all of the parts and hardware. The speedometer reads around 13000 miles (I don't know if it is working though). The engine still has oil in it and rotates freely. The sleeves show minimal wear - in fact they look great! I think the major issue is going to be to make sure the carburetors don't have serious damage to them and then to make sure the magneto does its thing.

I hope this update sparks additional feedback - I will use all the help I can get. Thanks to all for providing feedback and links so far! It is much appreciated.

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Darryl.Richman
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Max BMW will be able to help

Max BMW will be able to help you with parts, and things like the fenders are available new from them. I bought a new rear fender for my /3 from BMW and it fit perfectly. While not cheap, the price was not expensive either, compared to what modern plastic costs.

Post photos here and we can help you figure out what is right and what is added on.

Do not throw away the battery cover; if you don't want it (after your restoration work), there are others who would be interested. (Like me, for example.)

Is the speedometer actually in miles? I didn't think BMW supplied these bikes with mile speedometers, only kilometer speedos. The speedometer should be a Veigel unit, not a VDO, with a black face and white numerals. (VDO is the merged company of three instrument makers, Veigel, Deuta and Ota.)

If you want to get an idea for how much mileage is on the bike, look at the foot brake lever. The top has a pyramid pattern. If the points are still sharp, then the bike may have fewer than 20k miles on it. If the pyramids are worn flat, then the bike probably has more than 100,000 miles on it.

These bikes did not come from the factory with a sidestand of any sort. There was an odd, aftermarket item that was a clip that folded out from the left rider's footpeg. Later on, there were other sidestands developed. The problem with not having a centerstand is that kickstarting the bike on a sidestand is likely bad for it, and may also be bad for the area of the frame where it attaches. New centerstand parts are available, but you will also need to check that the holes in the mounting tabs on the frame are not wallowed out, and that the points on the frame where the centerstand supports it are not bent or damaged.

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schrader7032
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Sounds like your "real" major

Sounds like your "real" major issue is the oil leak that the previous owner was struggling with. A true oil leak would be bad...a bit of misting or oozing would be secondary, depending on your level of anality.

Picture 16 on this site might be the stand that Darryl is referring to. It was somewhat problematic and often didn't stay up.

http://www.brooksmotorworks.com/photo-gallery/what-we-ride

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'78 R100/7 '69 R69S '52 R25/2

stephan.pretorius
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Derry, NH
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More

Darryl,

You are correct: the motorcycle is marked in kilometers - the reading on the dial is 13880km (an honest to goodness Veigel unit). The pyramids on the brake pedal are indeed sharp. I also verified the side stand that Kurt referred to in pic16 of his link and it is indeed the one.

The tank and seat came off tonight along with the baggage porter. It was great to see the frame exposed. I can finally see the shape of the original motorcycle.

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Darryl.Richman
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Ok, you definitely have the

Ok, you definitely have the period aftermarket Akip sidestand. But I think your bike, on balance, looks like it's a 1953 year bike. I say this based on the duplex (or double leading shoe) front brakes, the rubber gaiters on the forks, the aluminum wheels (which generally only came on an R68) and the shroud around the hardy disk between the transmission output and the driveshaft. Most of these things came in no earlier than 1952. OTOH, as there's no brake light switch nor the amber triangle on the taillight housing, the bike should not be newer than 1953. Not to mention having the half width hubs. Actually, I can't quite tell, but it looks like those hubs may not have any fins running around the circumference. If so, those hubs cannot be for anything newer than a 1950 R51/2.

As you have surmised, the fenders are not original, but neither is the throttle, nor the mufflers. The buckhorn style handlebars might be stock US issue, but the two risers from the triple clamp are, at best, for an R68. The rubber gaiters on the plungers are not original. The tank looks like a period aftermarket item, but I'm not really sure.

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R68
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...HOLY TOLEDO!!! You have a

...HOLY TOLEDO!!! You have a Lugauer racing tank and Meier racing hubs on that bike...these are some of the true unobtainium parts for these bikes. I'd imagine that your bike was a privateer or weekend racer. The aluminum fenders are for weight reduction...fascinating machine...

R68
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...also, racing mufflers

...also, racing mufflers (loud, no restriction), a racing throttle (Magura Quick), and rear plunger gaiters (less weight)...weird seat and the ape hangers maybe just personal preference of the original owner? The throttle and the clutch/front brake controls likely came from a Zundapp KS 601, a much improved design as compared with the contemporaneous BMW items...

stephan.pretorius
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Derry, NH
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The rims are engraved with

Borrani 19x3 Record...

I have a set of Bing carburetors on the motorcycle and I was able to fairly easily remove the sliding part of the carburetor from the first one, the second is stuck. I sprayed some of my Remington lubricant in there and will let it soak overnight. Any advice on how to release sensitive parts like that?

I verified the frame number again and it a 518XXX number.

There is a key barrel (loose) in the fork/front wheel assembly. The light has a rotating lever switch and then there is another rotating dial...Any idea what this dial may be for? Another question: why do these motorcycles have batteries?

Is this forum an appropriate place to be looking for parts? If so, is there a specific place where such requests/searches should go?

Once again thanks for all the help and the feedback. This would be my first restoration and I do not want to screw it up.

With much appreciation,
Stephan

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schrader7032
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Entering 518xxx into the

Entering 518xxx into the frame number search button on the left side of this page indicates the bike is an R51/2. I entered 518111 just to get a number within the range.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

stephan.pretorius
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Derry, NH
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Oops!

Kurt - thanks for the check...I listed the engine number (518xxx). The frame however is a 525xxx number. Are the two numbers supposed to match? From the records, it seems as if the the engine is a R51/2 while the frame is a 51/3. The plate on the frame reads 51/3...

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Stephan Pretorius
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R68
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OK...it seems that you have a

OK...it seems that you have a post 1951 motor in an R51/2 mainframe with upgraded R51/2 front end, a 1953-57 aircleaner, and a Hella tailight, which is to say that you have a "missmatch", or in the British vernacular, a "bitsa" bike. We can't tell what exact motor you have, but I suspect that it's not an R68. We need more photos. The gearbox is also post 1951, ie. R51/3-R68. I see that you live in New Hampshire? There's alot of interest in your type of motorcycle around there and throughout New England. If you ask around, I'm sure you'll find folks who can help you with your project. The parts you would need to restore that bike are somewhat expensive but not too hard to find. I'd suggest that you not try to do a full restoration, but keep the bike as a gentleman racer. We need more pictures, and the motor serial number.

schrader7032
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There is a list which shows

There is a list which shows orphan engines and frames. Maybe one matches your "bitsa" parts...

http://bmwvmca.org/joomla/

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Darryl.Richman
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A 525xxx frame is an R51/3

A 525xxx frame is an R51/3 frame. A 518xxx motor is an R51/2 motor. In this era of bikes, the motor and frame numbers should match.

Borrani wheels would have been added by some previous owner.

The Bing carbs should have numbers stamped in them, downstream from the mixing chamber, in the form XX/XX/XX.

Quote:

There is a key barrel (loose) in the fork/front wheel assembly. The light has a rotating lever switch and then there is another rotating dial...Any idea what this dial may be for? Another question: why do these motorcycles have batteries?

The fork lock on these bikes was an option, and a strange one at that: the lock and key were kept in the tank toolbox (which your aftermarket tank doesn't have). After parking, the owner would turn the handlebars to line up the hole in the triple clamp with the machined boss on the steering head and insert the lock, with its key, into the hole. Then the key was turned and removed.

I can't understand exactly your description of the headlight bucket. There should a be a small hole, forward of the speedo, into which the "spike" key is inserted. All of these bikes have the same spike, its a short steel dowel with an oblong plastic head. The spike is inserted into the hole and then pressed home to enable the bike to run. The plastic head also allows the spike to be twisted left or right, which turns on the headlight or parking light. This is probably what you're seeing as a "rotating lever switch". But the dial? Confused

The battery has a two part answer: for an R51/2 bike, the battery was necessary because it has a battery/coil ignition. For an R51/3, the battery is only there so that the electrics (lights, horn) work while the engine is idling or stopped. On both models the generator doesn't really get going -- and the red light goes out -- until you're at about 2,000 rpm, which is well above idle.

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stephan.pretorius
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This is all very good info - THANKS!

Frame number is 525581 and the number on the engine is 518698

I really value the input. I am going to take more pictures and will post them in time.

Darryl: I am making the assumption that the intent was to remove the "spike key" correct? I could get mine to pop up and to rotate...If yes, I guess I'm going to have see if it does under greater force.

About the battery: so if the engine number indicates that this is indeed a R51/2 engine, I would need the battery to kick start the engine correct? I thought I read somewhere else that the R51/2 had a different exposure of parts around the top of the engine (underneath the tank)...

"Rotating dial": this sits on the yoke of the steering behind the handles and in hindsight, it looks more like a tall wing-nut than a dial

Thanks once again and blessings on your day

Stephan

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New Hampshire, USA
stephan.pretorius
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The tall wing-nut

The tall wing-nut turned out to be a tensioner on the steering column. It adjusts the height on a claw shaped belleville washer...I did find the numbers on the Bing carburetors on my way out this morning and when I got to work I forgot what they were - something like 1/48/25 and 26 maybe? I'll verify again tonight

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Darryl.Richman
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Here's a top photo of my 1953

Here's a top photo of my 1953 R51/3. The "knob" directly ahead of the speedo is the spike. With some force, it can be completely removed from the headlight shell. When inserted into the shell, there are two "captured" positions, part way down and fully down. Fully down enables the ignition, and engages a small tang that allows the knob to swing left or right to engage all the lights or just the taillight and parking light.

The red light to the left of the spike is the generator light. On all BMWs of this general era, the generator light should burn brightly when the spike is fully seated with the engine stopped (indicating a good battery) and while the engine is running at idle (not turning the generator fast enough to match the voltage of the battery). As the engine speeds up from idle, the light should gradually go completely out.

The dark red plastic button opposite the generator light is a screw out cover that holds the 8amp torpedo style fuse, which protects all of the lighting and horn circuitry.

The speedo we've talked about. The green light, not present on the R51/2 and earlier models, is the neutral light. Inside the headlight shell there's a small circuit board located below the entrance for the spike. Power comes from the board to the neutral light, and thence on through the wiring loom back to the area of the battery. A brown wire should exit here and proceed to the rear right side of the transmission, where it enters a small tunnel cast in the small cover on the right side (same cover has the hand lever). There's a small set screw under a rubber plug to capture the wire. The circuit is normally open, but shunts to ground when the transmission is in neutral (which completes the circuit and lights the light).

The hole in the triple clamp just to the left of center is where the optional fork lock can be applied.

The little chrome switch on the left side of the handlebars is the hi/lo beam and horn button.

The big wing nut is, as you've discovered, the adjuster for the friction steering damper.

The gas tank is the stock item for an R51/3. An R51/2 would have a slightly smaller tank and the toolbox door, like all of the prewar bikes, opens to the right. The chromed round screw holding the door closed takes a square cross section "key" to use as a screw driver to hold the door closed and provide some security.

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Darryl.Richman
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I was just looking at your

I was just looking at your photos again. Regardless of the number stamped in your motor, that is not an R51/2 motor. You are right that the look of an R51/2 (and earlier) motor is different from an R51/3 (and later, through 1969). Check the number again, and then enter it into our serial number decoder on the left sidebar of any page on our site, near the top (under the "BMW Models" heading). The motor in your photos came stock with a magneto ignition and wouldn't have required a battery to start and run.

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R68
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I think you motor number is

I think you motor number is 525581 from an early R51/3, and you carbs are 1/22/41-42 if original to that motor, and 1/22/39-40 if left over from R51/2 that you bike started as. As you see, 22mm carbs are used on the very early R51/3. Whoever rebuilt you bike used the gearbox from the R51/3. Maybe they also took the headstock plate off from the R51/2, and replaced it with the same from the R51/3? The motor number is found just above the pushrod tubes on the LHS of the case. The frame number is found on the LHS top rear plunger mount.

stephan.pretorius
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Derry, NH
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more pictures

The feedback on my postings prompted me to take and post a lot more pictures...thank you one and all for the advice and helping me through this process. All comments are welcomed - even if it is about something you see in the background. One of the pictures show a ball-end at the bottom of the right rear shock. Do we know what this interface is for? As you will be able to tell, I completely screwed up the carburetor number. The frame and engine numbers are as reported...

Thanks everyone!

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Stephan Pretorius
New Hampshire, USA
stephan.pretorius
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a little browsing brought me to this site

http://www.altmuehlnet.de/hp/mayerfranz/R51-3_B.htm

As you can tell from the pictures, the motorcycle also has the chrome mudguards...

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R68
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I'm stumped on this one: I

I'm stumped on this one: I can't explain how an R51/2 serial number got on an R51/3 type motorcase! The carb is original to an R67/2-/3...but you still are fortunate to have found such an interesting motorcycle!

schrader7032
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The ball-end is what a

The ball-end is what a sidecar would attached to. There are/should be other attachements on the right side of the frame.

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'78 R100/7 '69 R69S '52 R25/2

stephan.pretorius
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Update!

I thought I'd post an update.

A very kind gentleman gave me good advice: he suggested I get the motorcycle running prior to spending any money on anything. I'm happy I did, as it really charged my batteries once I got going. I have mentioned before that the heads came off awhile ago. I found the heads wrapped in newspapers dated 1971. The engine went together without any hickups and a friend let me borrow his carburetors to use for the test. The youtube link is the go no-go test...IT SOUNDS HEALTHY!

http://www.youtube.com/watch?v=uR81YPbOyis

So the motorcycle is now completely apart (except for the front fork assemblies). I will probably get to them after this email. The frame is going in to get powder-coated. I am including 2 pictures: one of the frame and the other of the engine getting cleaner. It's not completely clean yet, but in comparison its starting to look a whole lot better. I don't know if I mentioned this before but I found the motorcycle it had been sitting underneath a deck in the dirt in New England. Removing the air-cleaner I found a critter nest in the air cleaner housing.

My friend have been encouraging in almost every email to clean, clean, clean. Well I can tell all of you this, I've put in hours and hours of elbow time behind a tiny little brass brush. I think I'm going to stop throwing them out just to keep count of how many it took to clean this motorcycle.

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R68
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You have some peculiar

You have some peculiar modifications to your main frame. (Lower down tubes, fore of battery tray, and tank bracket) You should connect/compare frames with your countryman who just found a basketcase R68. This fella not only has the correct front end, but even the correct one-year-only Eberspracher aircleaner! I think the plate is french?

schrader7032
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I used a green scotchbrite

I used a green scotchbrite pad and WD-40 to do some cleaning on my R69S engine. Since I was doing a complete bottom and top end, I actually used the high pressure hose at one of the local hand-held car wash places. Other things to consider is NeverDull and Simichrome. Be careful with too much rubbing...you can really change the texture if you get too agressive.

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The frame on your bike has

The frame on your bike has been modified in the past to accept a war surplus R75 motor; probably to go racing. The extra brackets on the front of the downtubes that R68 noticed, accommodate the R75 motor, which is the only air cooled boxer BMW motor with a different spacing between the motor mounting studs. We had an article in the Vintage BMW Bulletin (v37n2, Summer 2010) by an anonymous German author showing a recent build of such a bike. Often the R75 motor was sleeved and/or destroked to get a 500cc displacement, in order to fit into that popular class.

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R68
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...that's fascinating, I've

...that's fascinating, I've never seen that modification to accept an R75WH motor! If it were my frame, I'd leave those intact?...

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I would certainly leave them

I would certainly leave them on the frame, and I would also try to find who did it and when the modifications were done.

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A closer picture

I went back to take a closer look at which modifications you were referring to and yes I can tell it has been a after-the-fact modification. I took 2 additional pictures with my telephone. See attached. I would certainly not consider removing those features as they have compromised the original stress-bearing members during the insert.

R68 sent me a link awhile ago to trace the origin of my frame and engine numbers and both were sent to a motorcycle dealer Göhler in Karlsruhe, Germany. Any modifications to the frame may have happened there...

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Rear gaiters

The 4th picture I posted on 12/13/2010 is one where the rear gaiters on my motorcycle is in view. I count 12 ribs on the gaiter and I measured last night the ID is around 2.3" or around 58.5mm. Does anyone have any idea where I can find replacement gaiters (bellows) to match this? I found a BSA part, but it is 2" in diameter at the interface.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2606271102...

Any help would be appreciated please
Stephan

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Stephan Pretorius
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The rear gaiters are a post

The rear gaiters are a post war racing accessory, and I'd suspect they were not specifically made for the this BMW application, ie, use whatever you can find that fits? Josef Heft may have them, or know where to find them.

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The rear gaiters are a post

The rear gaiters are a post war racing accessory, and I'd suspect they were not specifically made for the this BMW application, ie, use whatever you can find that fits? Josef Heft may have them, or know where to find them.

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Rear gaiters

The link to the BSA/Triumph gaiters or faltenbalge is the correct one. The 12 ribs is correct and the 2 inch diameter is sufficient to stretch over the aluminum brackets at the top and bottom of the rear suspension spring. I have a set on one of my bikes, and this is exactly the same gaiter I used. Should work fine. Good luck and keep us posted on the progress. Heft does not have them. Buy them cheap on Ebay or at your local vintage Brit motorcycle shop.

Scott

  • faltenbalge.jpg
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Scott, where did you find

Scott, where did you find those nice looking Beru strap clamps?

Please let me know,
Stephan

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Gator clamps

My gator clamps...

Thanks to everyone who's been following and posting...

  • beru.jpg
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Progress report

A friend told me about this tank on eBay and I was very fortunate to be able to buy it...It took a few days to get here, but the wait was all worth it. It showed up without a key and badges, but that is the way it was advertised on eBay. Here are some pictures.

I also bought tires and the rest of the gummy accessories I need. next thing would be to powder coat the hubs and send that ad the rims out to get re-laced.

  • img_2437.jpg
  • img_2439.jpg
  • img_2440.jpg
  • img_2441.jpg
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Stephan Pretorius
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Air inlet tubes

So the old air intake tubes took a beating - they have surface rust on them (right through the chrome). What is the best way to make them look new again? Have them re-chromed, or is that not an option? I also have a spot or two on the rear shiny cover of the drive-shaft that would need the same kind of attention.

I also included a picture of my frame after it came back from being powder coated

I appreciate all inputs.

Kind regards.

  • photo-2.jpg
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You should be able to have

You should be able to have the intake tubes rechromed. The bell cover over the U-joint is aluminum; it might oxidize but it shouldn't rust.

Your frame looks great! I hope you have no problems with overspray in the various holes, and that the numbers are visible.

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Thank you Darryl...I will

Thank you Darryl...I will take pictures of what I see on the drive shaft and post those as well.

I also just received the rest of the parts back from the paint shop who did the powder coating and the guy was a little ambitious (like coating the inside of my hubs). I mentioned to another member that the motorcycle already cost me $20k just in cleaning man-hours - I'm sure a few extra trying to remove excessive paint won't break the bank...

Re. numbers: what numbers? - who wants to see the numbers on a mismatch bike in any case?

Have a fun weekend!

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Bell cover

Here's the picture of what I was talking about. It is not aluminum. The dark spot you see is rust...What is involved in the disassembly?

  • photo-5.jpg
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I've never seen a bell cover

I've never seen a bell cover that wasn't aluminum! Unfortunately, removing the bell cover and the rubber bung are annoyingly difficult.

I see that you've got the final drive and driveshaft free from the bike. That makes things somewhat easier.

The bell cover has a left handed thread, and can be removed from the nose of the final drive with a pin spanner. (In fact, there's no reason to tighten this more than hand tight, but because of the left handed thread, they tend to get tighter over time, and you'll probably need the spanner to get it loose.)

Once you move the rubber bung forward on the shaft and loosen the bell cover, you'll see the U-joint. Behind the U-joint there is a pretty substantial pin with a nut on it, locking the end of the driveshaft to the front of the final drive. Remove the nut and drive the pin out from the nut side. Then you can slide the driveshaft off the splined connection to the final drive. Before you forget, mark the nut side of the final drive spline and the same side of the driveshaft. The pin only goes in one way; if you get the combination wrong, it will stick half way and tend to mung up the pin.

Now that you have the driveshaft off, comes the hard part. To get the bell cover and rubber off, you must press off the driveshaft flange from the front end of the driveshaft. You must accurately measure or mark the depth of the flange on the driveshaft before you do it, because there's no stop or mark when you go to put it back together.

Since the flange takes all of the driving force of the engine and all of the braking force of the rear wheel, you can imagine that this must be a very tight interference fit. You must support the flange fully before pressing out the shaft or risk deforming it. When reassembling the pieces, the machinist I use heats the flange over 350F/175C to get some slight expansion, but it still takes a lot of pressure to put it together. I seem to recall that it was about 3 tons.

New (aluminum) bell covers and rubbers are available. Or you can have yours rechromed.

If you find that the U-joint is notchy, then the joint is bad and you need a new driveshaft. The prewar driveshafts could be disassembled and the bearings replaced, but the postwar shafts are tack welded. Still, a good machinist can generally grind off the welds, replace the bearings and tack it back together again.

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Bell cover

Darryl,

Thanks for the detailed feedback...I will take a better picture because there is something else on the bell cover that probably warrants expert opinion as well: it seems as if the bell cover was deformed in 4 places along the circumference to prevent unscrewing.

BTW you correctly identified the mounting locations for the R75 on my frame. Do you think the drive shaft on my motorcycle may be a remnant of the mods done earlier. May this bell cover (or the whole drive shaft assembly) be from a different model? I keep in referring to my motorcycle as a R51/3 when that only describes the engine. The frame is indeed a R51/2...the question then becomes where is the split between the R51/2 and the R51/3

Thanks for looking and weighing in!
Stephan

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I don't think that your

I don't think that your driveshaft is from an R75. That bike had no rear suspension, and no need for a U-joint. New bell covers were not available for a long time in the 80s and 90s, so perhaps someone made a new one for your bike.

Other than the motor (not a small detail), there are not a lot of differences between an R51/2 and an R51/3.

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Replacing the wheel bearings

So if we replace the wheel bearings, especially the ones in the back, with the 2RS type (dual rubber seals), how does grease get to the spline interface where the hub meets the driveshaft? In the open bearing design, the grease was able to migrate through the bearing, beyond the labyrinth seal right onto the splines, or am I missing something? At the capture nut side, I see there is some sort of a fiber packing for grease containment (open bearing design). I modeled the internal components of the rear hub in solidworks and will post a x-section tomorrow.

Please weigh in.

Thanks,
Stephan

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New Hampshire, USA
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I've not seen an R51/3 but it

I've not seen an R51/3 but it must be similar to all of the bikes of the period. There's gear oil in the final drive which lubes the driveshaft and final drive gear set. The wheel bolts to the final drive and the splines between them are external and are lubed with a good tacky kind of grease. Honda Moly 60 paste is a good product. I actually mix some Chevron NLGII red tacky grease with about 30% moly grease.

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Hub Assembly

I understand my explanation of my question was a little confusing...I am including a picture of a cross section of the hub. The yellow arrow indicates the path of the grease originating from the external grease nipple on the hub, allowing it to reach the spline interface

I tried to be accurate with the modeling. If interested, I will make them available in edrawing format. email: stephan.pretorius at gmail dot com

Edrawings is a free viewer

  • hub_assy.png
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Very excellent diagrams, but

Very excellent diagrams, but the wheel bearing lubrication has no relationship to the hub spline lubrication. The spline lubrication is much less sophisticated, merely done with the wheel removed. The "external grease nippel" you mention is only found on the pre 1951 hub, presumably deleted as useless afterwards. Maybe you have those early hubs on your motorcycle? Wheel bearings need to be greased after removal from the hub, and we ALL use the nice little tool to remove the wheel bearing retainer don't we...folks who damage the four wheel bearing retainer holes with a drift pin are to be castigated!

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