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Thread: Motor Oil recommendation for r50 /2

  1. #1
    boxerotto
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    Motor Oil recommendation for r50 /2

    The BMW manual recommends W40 oil , so I’m using a modern 20W50. Is there any issue using a modern oil since the motor does not have an oil filter. Any recommendation on cleaning the motor from oil deposits? What is the best oil to use?

  2. #2
    Cam Killer marchyman's Avatar
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    What is the best oil to use?
    Clean oil. Cleaning the slingers is a pain. Enough of a pain that most change oil quite frequently, e.g. every 1000 miles or so. I'm currently using name brand 10W-40 in my R69S. I've used name brand 20W-50 in the past. I've used synthetics, semi-synth, and even BMW branded normal oils (back when they were $4/qt). Choice most likely depended upon which was on sale when I last bought a case.

    // marc

  3. #3
    Cannonball Rider #52 darrylri's Avatar
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    If you thought that dreaded oil threads were unresolvable for modern bikes, you're really asking for it when you try to figure out what to do for a vintage bike.

    Some people believe that you should run old fashioned, nondetergent, straight weight oil in your pre-70 bike, because, as you observe, there's no real oil filter, and therefore, detergent oil will loosen the sludge that has accumulated inside your motor and run it all into the slingers and some of it through the main bearings and conrod bearings.

    Some people believe that modern, multiweight, detergent oil is better because it holds all of the dirt, combustion byproducts and cylinder wear in suspension and, when you change the oil every 1,000 miles like the manual recommends, you will get it all out of your engine.

    Some also feel it's important to stay with a "motorcycle" oil, one that has the SF or SG API rating, because later ratings have less ZDDP and other antifriction agents in them (they harm catalytic converters, so they have been phased out).

    Others observe, however, that heavier oil grades like 20W50 are not (necessarily) subject to this regimen because they are not subject to the API's "energy conserving" logo (pumping oil sucks up a certain amount of power via the oil pump, and thinner oil takes less than thicker oil), and anyway, any modern oil is going to be better than what was available in the 50s and 60s.

    There's more, believe me.

    If you want to clean the motor, then you'll need to pull it down to the bottom end. Then you can use a power washer or an ultrasonic tub on the block, and this will give you a chance to clean/replace the slingers and check the bottom end while you're at it. Depending on who you talk with, this kind of service is recommended every 30-50k miles. (Yes, I know that there are people who have put many more miles on their /2 motor without anything more than routine maintenance.)
    --Darryl Richman, forum liaison
    http://darryl.crafty-fox.com

  4. #4
    boxerotto
    Guest
    Quote Originally Posted by DarrylRi View Post
    If you thought that dreaded oil threads were unresolvable for modern bikes, you're really asking for it when you try to figure out what to do for a vintage bike.

    Some people believe that you should run old fashioned, nondetergent, straight weight oil in your pre-70 bike, because, as you observe, there's no real oil filter, and therefore, detergent oil will loosen the sludge that has accumulated inside your motor and run it all into the slingers and some of it through the main bearings and conrod bearings.

    Some people believe that modern, multiweight, detergent oil is better because it holds all of the dirt, combustion byproducts and cylinder wear in suspension and, when you change the oil every 1,000 miles like the manual recommends, you will get it all out of your engine.

    Some also feel it's important to stay with a "motorcycle" oil, one that has the SF or SG API rating, because later ratings have less ZDDP and other antifriction agents in them (they harm catalytic converters, so they have been phased out).

    Others observe, however, that heavier oil grades like 20W50 are not (necessarily) subject to this regimen because they are not subject to the API's "energy conserving" logo (pumping oil sucks up a certain amount of power via the oil pump, and thinner oil takes less than thicker oil), and anyway, any modern oil is going to be better than what was available in the 50s and 60s.

    There's more, believe me.

    If you want to clean the motor, then you'll need to pull it down to the bottom end. Then you can use a power washer or an ultrasonic tub on the block, and this will give you a chance to clean/replace the slingers and check the bottom end while you're at it. Depending on who you talk with, this kind of service is recommended every 30-50k miles. (Yes, I know that there are people who have put many more miles on their /2 motor without anything more than routine maintenance.)
    Darryl, Thanks for the detailed and objective summery. Suspending the carbon/abrasion particles and flushing with oil changes makes sense to me. Having taken apart many car engines since the early 80ÔÇÖs I know that the phenomena of clogging the engine with oil deposits has diapered with the introduction of modern oils. The change in tolerances between modern and vintage engines seem irrelevant since most bearings in the R50 are of roller or ball type ÔÇô totally different to modern engines. I wonder how requirements for ball verses sliding bearings on oils differ? Any Tribologiests in the forum to answer this specific question.



    Rolf

  5. #5
    Little Egypt Airheads
    Join Date
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    I run a good 10W40 oil in my R50/2. No problems. I feel 20W50 would be a little thick for the low volume gear pump in this machine. The "10" part helps to get the oil working faster in cool weather, too.
    I did make another change. The manual calls for the same 10W40 in the transmission. I switched that to 85W90 gear oil and it works fine, too.
    Little Egypt Airheads
    '66 R50/2
    '80 R100RT

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