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Thread: Cylinder head identification

  1. #1
    Registered User LCampbell's Avatar
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    Cylinder head identification

    I have a left cylinder head that is used on a custom application that I am trying to identify because I may have to replace it. The part #'s on the head are 1 251 595 9. Intake valve dia. = 38mm, Exh. = 34mm. It's also possible that the valve sizes are not stock. I'm thinking it might be off of a R50/5 but my old part # book doesn't go back that far.
    2011 R1200RT, 92 R100RT, 75 R90S, 70 R75 Race, Vintage Kneeler sidecar R75 powered

  2. #2
    R69S, R60 and R65, from my notes. R50/5 was 32/34.

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    Anton Largiader 72724
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    Virginia Motorrad Werkstatt BMW motorcycle service and repair in central Virginia

  3. #3
    Liaison 20774's Avatar
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    Quote Originally Posted by LCampbell View Post
    The part #'s on the head are 1 251 595 9.
    Those are more likely mold numbers and not part numbers. BMW didn't stamp numbers on parts.

    34mm exhaust valves are part number 11341256679. 38mm intake valves are 11341256678. You can use those numbers in RealOEM to find all models that used that part number.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  4. #4
    Actually that will be a part number, it's just not a retail part number. It's the part number for the casting and the full part number would probably be 11 12 1 251 595. The last seven are the unique part number and the first two groups are main group (11 = engine) and subgroup (12 = cyl. head). The 1 251 595 part puts it around 1970, so that casting was added to the system around then, making it likely to be an R50/5 head. A few pictures would help.

    As with other castings like wheels, you have a rough part (with a part number) that gets secondary operations like machining, painting and added components and ends up with one of several other part numbers. In this case the casting gets machined for combustion chamber, valve seats pockets, guide bores and other machined surfaces depending on the engine (possibly getting another part number at that point) and then gets seats, guides, center stud and other stuff installed to get to the retail level.
    Anton Largiader 72724
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    Virginia Motorrad Werkstatt BMW motorcycle service and repair in central Virginia

  5. #5
    Registered User LCampbell's Avatar
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    Hey Anton. Thanks for the info. The heads are on a Vintage racing sidecar we have & the heads came with it. They have been modified with a welded on inlet spigot for a 32mm Dellorto carb & the exhaust spigot has been cut off & bored out for slip in exhaust headers held on by springs so I'm thinking the valve sizes are not stock. The holes in the fin are for the pins that hold the exhaust header springs & it's dual pluggedsidecar heads 001.jpgsidecar heads 002.jpg
    2011 R1200RT, 92 R100RT, 75 R90S, 70 R75 Race, Vintage Kneeler sidecar R75 powered

  6. #6
    Liaison 20774's Avatar
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    The date stamp has been cutout by the drilling in the fins. It's either 69, 79, or 89. My guess is it was 69, meaning they are probably /5 heads...they don't look like R69S heads based upon my own pictures.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  7. #7
    They are /5 heads, with the cast-in steel tube. The valve sizes you cite are stock for the R60/5, but they could be R50/5 heads that are modified. I don't know how the combustion chamber differed between those two.
    Anton Largiader 72724
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    Virginia Motorrad Werkstatt BMW motorcycle service and repair in central Virginia

  8. #8
    Registered User LCampbell's Avatar
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    Thanks for the info. It's a big help & a starting point
    2011 R1200RT, 92 R100RT, 75 R90S, 70 R75 Race, Vintage Kneeler sidecar R75 powered

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