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Thread: K75RT altitude plug

  1. #1
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    K75RT altitude plug

    I bought an altitude plug (contact ring) for my trip through the mountains but it came with no instructions. Where does it plug in?

  2. #2
    24991 Pauls1150's Avatar
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    On my '87 K75S, it was under the rear of the seat on the left side.
    But it really didn't seem to make much difference, it still idled poorly on Mt. Evans...

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    If you would look at the other thread that you started:http://www.bmwmoa.org/forum/showthre...-trip-on-K75RT
    where you asked the same question, you would see the answer. It was answered yesterday right after you posted the question.



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    Quote Originally Posted by Pauls1150 View Post
    it still idled poorly on Mt. Evans...
    You have other problems if it idled poorly. Chances are your base mixture is wrong or the valve adjustment is wrong.



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  5. #5
    24991 Pauls1150's Avatar
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    Probably too lean at 14,200 feet; but it ran quite well lower down. Many of the bikes (and cars) up there wouldn't run at all, especially the carb'd ones, so they'd coast down for a bit & then start!

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    Quote Originally Posted by Pauls1150 View Post
    Probably too lean at 14,200 feet; but it ran quite well lower down.
    Just the opposite. The higher the altitude, the thinner the air (less O2). Less O2 for a given amount of fuel = too rich. Exactly what the altitude plug is meant to help with. If your bike is running on the rich side to start with, then even with the altitude plug at altitude it will still be too rich.


    Easy test:

    1. Get your bike fully warmed up at the altitude where you live(ride it around for 15 minutes).

    2. Let it idle, note idle speed.

    3. While it is still idleing, push the starter button. Note idle speed.

    4. While it is stil idleing, install altitude plug. Note idle speed.

    If your mixture is correct, both #3 and #4 should cause the idle to drop and about the same amount (around 50 rpm). If starter button drops less or actually increases idle, you are running too lean. If altitude plug drops less or increases, you are running too rich.



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    Lee Fulton Forum Moderator
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    Quote Originally Posted by Pauls1150 View Post
    On my '87 K75S, it was under the rear of the seat on the left side.
    I don't know what you were plugging in, but the altitude plug socket is NOT under the rear of the seat.


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    Lee Fulton Forum Moderator
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  8. #8
    24991 Pauls1150's Avatar
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    'Twas a long long time ago with several bikes in between...
    All good info nonetheless.
    I've been looking on the A&S and MAX parts fiches - what page is it on? Ya got me curious now.

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    Quote Originally Posted by Pauls1150 View Post
    'Twas a long long time ago with several bikes in between...
    All good info nonetheless.
    I've been looking on the A&S and MAX parts fiches - what page is it on? Ya got me curious now.
    61_2725 Chassis Wiring Harness

    See link in post #3 above for link to picture of where it plugs in.



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    Looked on the link on #3 and it was not there

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    Quote Originally Posted by tullypilot View Post
    Looked on the link on #3 and it was not there
    What do you see in post #18 when you go to that other thread that you started (Need Advise For Long Trip K75RT? You need to be logged in to see the attachments.



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    Lee Fulton Forum Moderator
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  12. #12
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    Altitude plug location

    On my '92 and '95 K75's the plug is on the left side zip tied to the frame behind the side cover at the rear portion of the fuel tank. An exact type plug (low altitude plug) already plugged in.

    Charlie

  13. #13
    Registered User lkchris's Avatar
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    Quote Originally Posted by 98lee View Post
    You have other problems if it idled poorly. Chances are your base mixture is wrong or the valve adjustment is wrong.
    Back in the day high altitude problems with K-bikes were the result of vapor lock due to the superheated fuel.

    In any event, don't think there's any such thing as a "low altitude plug." It's either no plug for low altitudes or the special plug for high altitudes and if something's in there it's a high altitude plug.
    Kent Christensen
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    '12 R1200RT, '02 R1100S, '84 R80G/S

  14. #14
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    There is a dust cap (shown in the previously reffered to pictures) that comes inserted in the socket when the altitude plug is not being used.


    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
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  15. #15
    Registered User 58058D's Avatar
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    Many of us also did the spliceroo and installed a rocker switch in the dashboard where the key is. Then we could just toggle it into the circuit or not, depending on altitude. It did make a difference on my '85 K100RS.
    Jim Douglas '00 K1200RS >132,000 miles my primary bike again,
    Gone: '09 K1300S sold @ 22k mi, '93 K1100RS traded @ 78k mi, '85 K100RS sold @ 44k mi
    '06 Kaw 650R track bike sold
    http://www.seagullbb.com/

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