Rotax 650 Engine Rebuild (BMW)

Discussion in 'Thumpers' started by divimon2000, Dec 11, 2012.

  1. Spyker

    Spyker Been here awhile

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    Won't it be cheaper to order the complete gasket set rather than individual gaskets? When I rebuilt my Dakar I ordered the complete set.
    #61
  2. ericsbr

    ericsbr Adventurer

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    I did the math and the kit was more $ than the individual gaskets/seals i needed. I'm reusing the cam cover gasket. If not the kit may have been the better deal.
    #62
  3. ericsbr

    ericsbr Adventurer

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    [​IMG]

    More parts have arrived! New counterbalance shaft bearings are sealed vs old ones that were open. Every other internal engine bearing is open. Hmmm? What's better? Sealed are dependent on the grease that was put inside for its lifespan. Any wear particles are stuck inside too. Open bearings get constantly flushed and lubed with engine oil. Maybe better cooled by the oil too? Let the debate begin!
    #63
  4. divimon2000

    divimon2000 Been here awhile

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    My vote is for using what BMW currently makes (in this case sealed). Why? I have a feeling the boys at BMW engineering in Munich and the corporate structure of ISO 9002 (or whatever they use probably more sophisticated) for QA production naturally create a better part (in general).
    #64
  5. Spyker

    Spyker Been here awhile

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    I'm pretty sure BMW doesn't make bearings. They just repackage SKF, NTN etc.
    #65
  6. Spyker

    Spyker Been here awhile

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    By the way, when I pulled the bearings for replacement some bearings only had a seal on one side. the workshop manual states to press the new bearings in with the seal on the outside. So I pried one of the seals off the bearings.
    #66
  7. ericsbr

    ericsbr Adventurer

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    true. my old were NTN, new were NSK. each bearing maker prob has different levels of quality for different customer needs.
    #67
  8. ericsbr

    ericsbr Adventurer

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    what year is your dakar? what workshop manual were you using?
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  9. Spyker

    Spyker Been here awhile

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    I have a 2004 twinspark. Drop me a PM and I will send you the link
    #69
  10. ericsbr

    ericsbr Adventurer

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  11. divimon2000

    divimon2000 Been here awhile

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    That's a confirmation for sure. Sealed is better. Whaddya gonna do? Keep em as is, or you going rogue?
    #71
  12. ericsbr

    ericsbr Adventurer

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    dont rush me divimon! i still have time to flip-flop. could end up a coin toss. i would agree that sealed would be better if the engine/trans oil was very dirty or metal contaminated, but if the oil is kept clean and the engine/trans is "healthy" then more oil exposure seems better.
    #72
  13. mcma111

    mcma111 Long timer

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    Do your self a favor and pop one of the seals off and see how much grease is in the bearing. :huh

    You might decide that there is not enough lubricant for the long haul after all. If it were me I'd pull the seals and let the motor oil do it's thing but that's just me.
    #73
  14. Kawidad

    Kawidad Long timer

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    KTM did this same thing with the cam shaft bearings on the early RFS motors. The original ones were unsealed, to be lubed by engine oil. Then they were superceded by new bearings that were sealed. However, even though sealed they were still in an oil bathed environment. I spoke to some bearing experts (real professionals, not hacks) and they said KTM was crazy because oil is thin enough to seap into the bearing past the seals. When it does this it washes out the grease, but does not provide enough lubricant to keep the bearings running properly. KTM worked around this by recommending the bearings be replaced frequently.

    So I guess the point I'm making is that not all factory ideas are that good. (Not to mention, the original KTM bearings were the lowest quality/cheapest bearings sold in Europe (again according the bearing pros), which is mostly likely why they failed in the first place.
    #74
  15. ericsbr

    ericsbr Adventurer

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    what i have learned so far is not all sealed bearings are the same. wheel bearings for instance would be lubed for life with grease, and sealed to keep grease in and water and road dirt out.

    my new bmw bearings are designed for transmissions. they are greased only for initial lubrication, then the seal allows engine/trans oil to "leak in" to do the lubrication after the grease is washed out. they are designed this way.
    #75
  16. ferals5

    ferals5 Long timer

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    I'd be putting in unsealed bearings... I don't think either Rubber or Synthetic seals will cope with the temperature inside. :deal

    Just to give another point of view... from a spanner twister. :d
    #76
  17. divimon2000

    divimon2000 Been here awhile

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    Don't get confused with the word "sealed", thats what is making the discussion go off on a tangent. These are only sealed to keep the bad stuff out. The little lube in there is just for initial lube only, then the oil takes over. Its designed that way. Read the engineering and testing reports, pretty interesting that they've been using them since the 70's in autos with real good results (better than open for transmissions). Rubber doesn't breakdown, bearings do get oil, and they last longer. Don't take the mfg's word, read the data. I'm more sold now. Can't wait to start putting this thing back together, looks like Feb 8.
    #77
  18. ericsbr

    ericsbr Adventurer

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    been around since 1970s? i wonder why bmw and most everyone else is so late in using this better bearing technology.
    #78
  19. ferals5

    ferals5 Long timer

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    I'm not confused divimon :wink: I know what a sealed bearing is... are you referring to shielded bearings? By the description of a 'seal on one side' I will suggest that the bearing in question is in fact a shielded bearing not a sealed bearing.They operate in the same as open bearings allowing lubrication but stopping large particles from reaching the bearing. Shielded bearings can come in single sided or double sided. Not convinced that I would be too worried about large bits floating around in my rotax :eek1 Bearing failure will be the last thing on your mind...

    Sealed bearing come in so many types it's not funny... single lip ( pointing in or pointing out), double lips, V ring, diaphragm types, rubbing v's non rubbing etc etc but are designed to keep either lube in or crap out or both.

    hope this info helps

    cheers

    Mark
    #79
  20. divimon2000

    divimon2000 Been here awhile

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    Yeah all I'm doing is learning. I had no clue.
    #80