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Thread: R90/6 76 - smoke signals

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  1. #1
    Registered User plehman's Avatar
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    R90/6 76 - smoke signals

    Had a bit of time on my hands so I replaced the second, less bad side, push rod seals. Nice. No more oil on the sides and bottom of the pan.

    While I was at it noticed the left cylinder spark plug was black. Not the case on the right plug. Black is too rich - or so I think. After putting everything back, adjusting the valves a few times to get them "singing to me" and it was running nicely. So I pulled out my home made carb vacum sensor and worked on the balance, particularly in terms of rich/lean.

    With the carbs sucking equally, I dropped the left side down until it "bogged" then back it off a bit. Not too rich, not too lean. But I just noticed it's still smoking!

    Question. Other causes for smoking? could it possibly be rings or something.

    76 R90/6 40,000 miles only. Doesn't burn oil. Usually sits on the center stand.

    thanks guys.
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    Administrator 20774's Avatar
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    Worn guides? I seem to remember there are some on-road tests for this. Probably something to do at dusk, maybe with a partner behind you in a car. If you see smoke on acceleration, that would be rings. If you see smoke when you shut the throttle down while coming down a hill, etc., then that would be the guides.
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    #4869 DennisDarrow's Avatar
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    Please tell us that you are doing all of that carb tuning with a very strong fan blowing across your cylinders. Yes, they do overheat.........God bless....Dennis

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    Registered User plehman's Avatar
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    Well, I try to work quickly and in short bursts. Even take it for a short cool down. Never run for longer than a minute or two without moving.

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    Registered User lmo1131's Avatar
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    Please tell us that you are doing all of that carb tuning with a very strong fan blowing across your cylinders.
    ... and that you've undertaken your adjustments after thoroughly warming up the engine.

    A twenty-mile jaunt is usually considered sufficient; warming it up in the garage is not.
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

  6. #6
    Registered User plehman's Avatar
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    I usually adjust for rough or low idle when cold so it doesn't race when fully warmed up. But am still worrying that it's more than adjustment to get any smoke at idle.

    Checked the book and a value guide is the maximum difficult operation (5 wrenches). And it's for high miles bikes which this isn't. I gotta think this is mixture.

    Will work on that some more.

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