R100s piston rings

Discussion in 'Airheads' started by Stonegrasp, Jul 12, 2015.

  1. Stonegrasp

    Stonegrasp Adventurer

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    Hey guys back to the ole r100s that has been trouble. I've finally got her licensed and all so I've been able to ride and start the break in period on the piston rings. So far I've got 150 miles, but my oil consumption is ridiculous. 1 qt per 60 miles. The end gap is correct as well as the match in size to the cylinders. they are the deves rings from deves.com. a while ago i took the left side cylinder off and reoriented the oil control rings so their gap was between 30-150 degrees at varying angles of course, and that cut the consumption down so today I did that to the right side, but still losing oil. It comes out mostly at deceleration or acceleration so I think its the oil control rings? Any ideas, thoughts, comments, brilliant insights?
    #1
  2. Joel1

    Joel1 Been here awhile

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    Maybe through the valve guides?

    Joel
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  3. Dark Helmet

    Dark Helmet Go to ludicrous speed!

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    Have you done a leak down test since the rebuild? Compression test? It sounds like more than the oil rings to me to lose that much oil so quickly. Assume you honed the cylinders and got a good crosshatch?

    I just re-did my rings on an R75/5 and had no issues with oil consumption. Before I did the rings I did a leak down test and it was very clear that my rings were the issue. The sound coming out of the crankcase was like a wind tunnel, but intake and exhaust valves were dead quiet. Once apart I also did a solvent test on the valves and did not have a drip come through.

    Oil smoke on acceleration is rings, on deceleration is valves. I do not think a leak down test will tell you anything about the guides.

    DH
    #3
  4. Stonegrasp

    Stonegrasp Adventurer

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    Hey guys i should've mentioned and sorry it slipped my mind, I had the valve guides, valves, and valve seats replaced also at the same time. Ill perform a leak down test tonight or tomorrow, and i guess well see.
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  5. bmwrench

    bmwrench Long timer

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    Leak down tests aren't much help when it comes to oil consumption. If anything, the oil helps seal the rings and gives better numbers than you should get. Just take it back apart. If the problem is with the rings, the edge of the piston will be very clean, with a crust of black carbon toward the center.

    Did you modify the oil rings to make them easier to install? Is it possible you installed the second ring upside down? Did you use the expander behind the second ring?
    #5
  6. Beemerboff

    Beemerboff Long timer

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    Is your engine breather working properly ? How do the plugs look ? What sort of oil are you using? Less than a quart every 60 miles will oil up the plugs PDQ , but you haven't mentioned this, or what your fuel consumption is.
    But you might have damaged or incorrectly installed the rings, or just got a bad set, and a stripdown sounds like he only answer.
    #6
  7. Dark Helmet

    Dark Helmet Go to ludicrous speed!

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    Still think there is more going on there than oil rings alone, unless incorrectly installed, but even then a qt every 60 miles is a ton. It must drip out of the mufflers. My suggestion on the leakdown and compression test is to see if the rings are seating at all. Sounds like the head is solid after having guides and valve seats done so I would at least get a feel to see if the first and second ring are seated.
    #7
  8. Joel1

    Joel1 Been here awhile

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    As mentioned, burning that much oil has got to be making one or both plugs ugly. Have you looked at them to determine if it's one or both sides? Also, just cause the valves, guides, and seats were just replaced does not rule them out. I would still check the valve stem to guide play so that you can rule it out. You might also be able to tell something by looking into the intake and exhaust ports.
    #8
  9. Stonegrasp

    Stonegrasp Adventurer

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    Heys guys, srry working on this thing is slow, but i've done some poking around and it seems like Deves rings are not good rings for the old airheads. Anyone have experience with them? sounds to me like they are more meant for nikasil cylinders and my old girl is the older version. Anyway the oil is burning off not really coating anything. I have to get the bike warmed up for it to happen which is why i don't think its the guides as they would smoke on start up more, right because once warm they expand and "seal" against the valve, or is that just my ASSumption?
    #9
  10. bmwrench

    bmwrench Long timer

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    I've tried Deves rings in iron-bore motors, though in truth they were 1050 kitted. I had oil control problems with them, so I went to Hastings. These are available from Total Seal Piston rings. They don't sell them specifically for BMWs, so you need to supply the ring dimensions. If your pistons are standard, they are 94mm bore, 1.75/2.0/4.0 mm rings. Call them and ask for Ed Law. Or you can order them from me. These days, I get them with a "Napier cut" second, which really help with oil control.
    #10
  11. Stonegrasp

    Stonegrasp Adventurer

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    I suppose ill have to measure the bore again before I order but that sounds great, so can I just PM you when im ready and do it over the phone?
    #11
  12. bmwrench

    bmwrench Long timer

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    Yep.
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  13. 100RT

    100RT Long timer

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    You can also match them dimensionally with certain models of Volkswagen's.
    #13