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Thread: Setting timing for mid grade fuel '93 R100RT

  1. #1
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    Setting timing for mid grade fuel '93 R100RT

    I am replacing my bean can with a magneto from Motorrad Elektrik. I was using premium w/o ethanol but now I can only get midgrade w/o ethanol. My question is: where should the "S" be in the little timing window when I set the timing for midgrade fuel?
    Thank You for your advice!
    Campbell Tellman II

  2. #2
    Registered User lkchris's Avatar
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    Without your providing more information I'll assume either of the following:

    Your bike is an unmodified USA version which came with 8.5 compression pistons and was in fact designed to run on regular fuel.

    Your bike was modified with BMW 9.5 compression pistons and that's the only modification other than rejetting carbs to suit. You would have rightly run this configuration on premium fuel.


    In either case the timing is set the same. In fact, without changing the camshaft I've never heard of or believe there is a need to ever change timing from factory specification.

    So, do you have camshaft changes? Non-BMW pistons? Big bore kit? Dual plugs?

    BTW, addition of ethanol to fuel adds an anti-knock capability similar to what might have been achieved in the past with lead in fuel. Nevertheless, BMW's 1992 tuning did NOT assume ethanol or lead and there's never been a recommendation to change tuning when ethanol is added.

    Bottom line: setting timing for your bike is a non-event--just set to factory specs. Only ever worry about timing changes when you've radically modified your motor.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

  3. #3
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    A garden variety airhead . . . .

    Kent,
    Thanks for the reply. As far as I know it is a standard engine. (I like to think it is special tho . . . . )
    When I was riding a 1975 R90/6 I remember not being able to buy premium so I changed the timing to use regular,
    That little "S" was either higher or lower for the different fuel.
    That is the reason for asking . . .
    Campbell Tellman II

  4. #4
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    ethonal

    The only slight problem I've had on my 85 R80RT with ethanol gas was very minor popping in the exhaust. Where I live in Wisconsin, I can easily get ethanol free gas. I adjusted my carbs with this gas in the tank. When I rode down to Texas to visit my brother, I could only buy ethanol gas and the popping started when closing the throttle. When I returned to Wisconsin and started filling the tank with non-ethanol gas again the problem went away. I've reset the carbs after a couple tanks of ethanol so when I travel it won't be a problem again. It didn't seem to make any difference weather the non ethanol was mid or premium grade. frank

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