BMW R51 1939

[ogre]

Hello everyone,
I own a '39 BMW R51. Nothing matches in this bike but i bought it running few years ago and rode it without any problem.

Now i think its time to make it more original.
First thing i need is an engine case. Mine is r5 case 1936.
So if any of you got R51 engine case please contact me .
Also need Amal carbs.

All the Best,

Jack

[Darryl.Richman]

What a fun bike to have! I am sure that if you advertise for a while, you'll find someone who needs an R5 engine case and will find you an R51 case. The carbs will be very hard to come by and very expensive, but depending on which Bings you have, you might get a good jump on the cost by selling them off.

What's the little box under the tank?

You can get repop roundels for your tank that look correct for the period. Also, it looks like you have a /2 headlight bucket; even a /3 bucket would look more correct. If you get a set of steel rims and lace them to your hubs, someone will want the high-lip aluminum rims, and if they're 18" rims for a /2, you'll probably find that the bike is slightly faster with the original 19" rims. The mufflers are the postwar "swallow tail" style, not the prewar "fish tail" (but the swallow tail mufflers don't bite at errant ankles).

[Bruce Frey]

Hi Jack,

I got a spare R51 engine case when I purchased my R5 project. The number is 504723 and I would be interested in trading for the R5 case.

The only picture I have on this computer is attached. I am on the road right now and I won't be able to get any more until after Easter.

Cheers,

Bruce

[ogre]

What a fun bike to have! I am sure that if you advertise for a while, you'll find someone who needs an R5 engine case and will find you an R51 case. The carbs will be very hard to come by and very expensive, but depending on which Bings you have, you might get a good jump on the cost by selling them off.

What's the little box under the tank?

You can get repop roundels for your tank that look correct for the period. Also, it looks like you have a /2 headlight bucket; even a /3 bucket would look more correct. If you get a set of steel rims and lace them to your hubs, someone will want the high-lip aluminum rims, and if they're 18" rims for a /2, you'll probably find that the bike is slightly faster with the original 19" rims. The mufflers are the postwar "swallow tail" style, not the prewar "fish tail" (but the swallow tail mufflers don't bite at errant ankles).

Hi, i got r51/3 bing on my R51. I know they are worth some money.
I read somewhere on this forum that R51 also have bing carbs at the end of the production, can you confirm this?

The headlight shell was zundapp hella headlamp, already sod to usa
I was going to leave this alu rims as they are lighter than steel one. They are AKRON 19".
Mufflers and pipes already bought in Poland, look almost the same like orginal one .

The box under the tank is electronic voltage regulator. Works very good just need to hide it somewhere.

Hi Jack,

I got a spare R51 engine case when I purchased my R5 project. The number is 504723 and I would be interested in trading for the R5 case.

The only picture I have on this computer is attached. I am on the road right now and I won't be able to get any more until after Easter.

Cheers,

Bruce

Hmmm, if its in good shape, not welded i will be interested in.
Tell me how much do you want for your engine case?

Thanks.

Jack

[VintageSalesandRestorations]

You also have the 1936 only - non-finned - generator cover. Any 1936 R5 owner that doesn't have one would love to buy / trade you for the correct finned one. The correct Amal Fischer carbs will be expensive - you should be able to get them from Martin - oldiedoc@t-online.de - I am rebuilding the drive train on a 1938 R51 now - such an awesome machine - love that motor.

Jeff

[ogre]

Hi and thanks for that but i known this. Also front timing cover is from r5. Bmw r51 got mounting point to the frame on the top of this cover.
So what I need is engine case, top and front cover.

Hope the rest of the engine parts inside like camshafts and crankshaft are the same:)

Thanks for the amal cabs info will contact him asap.
Regards.
Jack

[R68]

Did you know that the heads and cylinders are indexed to the case, and if you have original 1936 R5 heads, these are impossible to find? Very few would use a rare and valuable R5 motor as a donor to build up a somewhat less rare and less valuable R51 motor??? As for the generator cover, Josef Heft sells a fine repop, but the '37-'50 finned generator cover is functionally much better: much better generator cooling and the spark plug wires will not melt! Maybe you should contact Lesek in PL, get an M72 converted to R5 frame, and build up an R5 with your absolute unobtainium motor?

[VintageSalesandRestorations]

Ah! I did not know that the early R5's did not have an upper engine mount - neat! The heads are usually stamped with the engine number near the valve cover gasket surface - in the valley between 2 fins. What do yours say?

Curious minds want to know...

jeff

[R68]

...getting very far out in the land of esoterica, but since you seem to be interested?...two pics showing a late '36 R5 in process of conversion to road race R5SS. Note absence of upper motor mount, placement of the bracket holding the extra plugs/plug removal tool that is really an upper motor mount, serial number on heads and cylinder foot, and very thin rocker support casting that's intact here, but usually rewelded after cracking on the R5. The R51 upper motor mount was added after they found that the case was cracking at the LHS rear motor mount bolt entry hole. To have a '36 R5 motor without such damage and with original unrepaired heads is unusual...also, AF carbs are basically for display, and Bings are less expensive, available, easier to restore?...I fear Jack is proposing take an R17 like motor to use as a donor to build a truck like R12?...

[ogre]