R80 Oil Burning Woes

Discussion in 'Old's Cool' started by Phreaky Phil, Feb 21, 2007.

  1. Phreaky Phil

    Phreaky Phil Long timer

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    Does Anyone Have A Close Up Picture Of The Top End Of A Later Model R100 Airhead Valve Guide. Do They Have A Champhered Step On The End? Apparently This Helps Scrape Oil Off. My Guides Have Been Replaced And The Guide To Valve Clearance Is Correct At 2 1/2 Thou But After Running There Is A Puddle Of Oil In The Inlet Under The Guide. The Engine Chews Oil And Has Carboned Up The Piston And Head Badly Causing Detonation. I Have De- Carboned Them And Removed The Engine Breathers From The Inlets. This Curred The Detonation But Not The Oil Consumption And The Cylinders Are Already Caboning Up After Only 1000km. The Bike Is A 92 R80 With A Sibenrock 1000kit Fitted. I Had The Pistons Measured Today And The Ring End Gaps Are Excessive But This Doesnt Explain The Oil In The Inlets.
    Any Ideas ?
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  2. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Two and a half thousandths sounds like a lot. I don't have a manual here to look at, but are you sure that's the correct amount of free play?

    There are only three places the oil could be coming from - past the rings, valve guides (intake), and the breather.

    How many miles (or km) have you put on the new rings? The chrome rings can take quite a while to break in and may be some of your problem.

    Did you stagger the rings 120 degrees?
    #2
  3. Phreaky Phil

    Phreaky Phil Long timer

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    Haines Manual Says Between 2 And 3 Thou. Hav Done 25000km On 1000kit. Bores Are Not Glazed. Yes Rings Were 120 Deg Apart And Oil Ring Gap At Top. Maybe Oil Being Sucked Past Guides And Ring End Gaps. Bike Did Not Use Much Oil As An 800. Had Valves And Guides Changed After 1000kit Fitted As I Noticed Oil In Inlets Under Guides With Carbs Removed.
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  4. Wirespokes

    Wirespokes Beemerholics Anonymous

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    The only way oil can get into the intake tract is from the breather. Either there is blowby which pressurizes the crankcase, or the breather isn't handling the increased displacement.

    But since you've run the breather somewhere else, that's not the problem now. BTW, did you run the breather into a catch bottle? Is there still significant blow-by?

    If there's oil under the intakes now, then it must be arriving from the guides. How else could it get there?

    I have no experience with larger end gaps. Out of curiosity, how much out of spec are they?
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  5. AntonLargiader

    AntonLargiader Long timer

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    They do have a scraper lip on them, but depending on how they were installed this could have been damaged. I've seen them hammered flat.

    Intakes don't wear that much, though. Exhausts wear out pretty quickly on the later Airheads.

    [​IMG]

    Left is an aftermarket guide, right is an OEM guide. Both have scraper lips; the BMW lip is shorter but sharper at the top. Both work well.
    #5
  6. Phreaky Phil

    Phreaky Phil Long timer

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    Ring End Gaps Measured, Top 25 Thou, Middle 23thou, Oil 32thou.
    Haines Manual Figures, Top 12-20 Thou, Middle 12-20 Thou, Oil 10-16 Thou. I Do Not Know What Siebenrock Recommend. I Ran A 1/2 In Pipe Out Of The Airbox For The Breather. Virtually No Oil Comes Out Of It.
    #6
  7. AntonLargiader

    AntonLargiader Long timer

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    Ring gaps look reasonable. Does the cylinder wall look glazed?
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  8. Phreaky Phil

    Phreaky Phil Long timer

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    Two People Have Looked At Bore And They Both Say Its Not Glazed
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  9. friar mike

    friar mike IronButtGruver

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    do a compession leak down test and that will anwser your ring question.
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