Forum bmwbike.com

I have a BMW R51motor framenumber 506302.

But the motorblok number 06038420 is not from a R51 who can help me and tell what motorblok this is and from what year. I think its a motor from a R51/3.

Motor is not original but verry nice to see and ride i think. I am verry happy with this motor.

Hi Richard,

Your engine is an R61, 1938 to 1941. Serial numbers 603001 to 606080.

Brock

Neither frame nor engine numbers match with any BMW numbers what so ever. They have obviously been changed.
The frame is postwar but could be anything from R51/2 to R68 as the photo is not clear. The motor could be anything from R51/3; R67 to R67/3 and even R50 to R60-2. Gearbox is definately R51/3 to R68 post 1951 with neutral indicator switch. Front brakes are simplex which would date the machine as a 1951 to 1952 R51/3 or R67 to R67/2.

Regards,

Mark
Mark Huggett GmbH

Richard, I have to disagree with Mark on the basis the first and last "0" are actually a BMW roundel to prevent people from adding numbers to the original serial number. If you take away the "0" at each end, your number falls within the R61 series. Comments? Thanks.

Brock
Canada

Brock,

If you dissagree with me, look at the jpeg that Richard posted and tell me if this is prewar...............If it is, I will resign now and eat a broom.

Regards,

Mark
Mark Huggett GmbH

Thanks for the answers but i still don't know it.

I did some thinking myself and i mean that the frame is a R51 because framenumber is 506302 see ( http://www.investment-bikes.nl/model/r51_1_~1.htm ) .

now the motor looks the most like R51/3 but the motornumber?? The answer from Brock Downey about the 0 xxx 0 is verry good to understand for me it sounds good.

But the motor not even looks like a R61 but like a R51/3 and i can see that between the black filter and the front of the engine they did cut some away look to the picture red marked.

If you need more pictures please say so because i still wants to know what kind of motor i have because my knowledge of old BMW motors is the same ass my english writing but i like my motor verry much.

You are wrong again about the R51 frame number. None of your numbers match up with any BMW numbers, so they have obviously been changed by somebody.
The last R51 frame number was 506172. Your number is 506302. The frame in the photo is 100% a post war frame, as prewar plunger frames did not have the cross tube running across the top of the motor which is clearly visible in your photo. That means that you frame could be from a R51/2, R51/3, R67 to R67/3 or R68. Their numbers are as follows:

R51/2 516000 - 521005
R51/3 522001 - 540950
R67 to R67/3 610001 - 617700
R68 650001 - 651453

To identify your motor without motor number, I need a close-up photo of the cylinders.

Regards,

Mark
Mark Huggett GmbH

Thank you for your reaction,

I believe you because you are verry wise about BMW but let me tell you wy i am confused about this.

You say that the last framenumber of a R51 is
506172, but when i must believe this link

http://www.investment-bikes.nl/model/r51_1_~1.htm

Not the last framenumber of a R51 is 506172 but the last ENGINENUMBER. This link say's that the last framenumber is 515164 and when my framenumber is 506302 i thought i have a R51 frame.

Now you see why i was so confused about this matter. I have zero understanding of BMW motor but started the day i bought my "BMW' i am in love with old BMW motorcycles. One day when i have a lot of money i will buy a old BMW original so i don't have to ask questions about this.

Thanks for your time and wisdom

Greetings from the Netherlands

Richard

Easy Mark, don't destroy your teeth just yet . My reference is to the serial number listed, not the physical engine. The serial number (less the zeros) supplied by Richard indicates an R61series according to BMW. Whether or not it is a correct engine for the serial number is another matter. Let me explain:

My pre-war BMW has BMW Roundels stamped at the beginning and end of both the engine and frame numbers. BMW Mobile Tradition has verified my bike to be authentic. Since Richard is new to the serial number issue, I believe he mistook the roundels as zeros, since the serial number in between the "zeros" is a valid R61 number.

The engine in the picture is another issue, it does not look like a pre-war engine to me either. Perhaps I should have made my initial statement a little more clear. Often, parts of our written conversations may come across as incomplete to the reader, compared to a two way spoken conversation.

It appears Richard has a BMW comprized of many different post-war parts, possibly from many different models, with an R61 serial number on his engine block. I agree, this does not automatically make it an R61. Somehow in the past it ended up with this number for reasons we can only speculate on. The bottom line is, Richard knows this now and enjoys his bike just the same. I hope this is an acceptable answer to all parties concerned.

Brock

Gentlemen, just found this interesting website of Mr Huggett.
I had once a similar problem with the identification of a R67 frame.
Untill somebody told me BMW also stamped the frame numbers in the upper frame tube...
hopefully this can help for the frame. For the engine, more detailed pictures would be usefull + what carburator numbers are fitted ?

Richard, ik meen te begrijpen dat je of Belg of Nederlander bent (alleszins nederlandstalig), neem gemakkelijkheidshalve direct contact met me op voor verdere assistentie.
mvg
Dirk
email : Hublou@hotmail.com