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Thread: gas mileage/setting valves

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  1. #1
    aapasquale
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    gas mileage/setting valves

    Last week I adjusted the valves and did a throttle sync and was very deliberate and careful about setting the valves a little looser than my last bout with the valves. My bike's engine has never run better for me...very smooth, good low end torque, and not even a hint of surging. The mileage is down about 4 miles per gallon and I was wondering if the more open valves would be inclined to do that. (by the way, my bike is a 1994 R1100RS, now with just under 50,000 miles on it)
    Thanks,
    Tony
    (I've just finished the major service myself)

  2. #2
    Benchwrenching PGlaves's Avatar
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    Valves a little looser to what?

    Down by 4 mpg to what?

    Looser valves does two things - it decreases total lift and open cross section, and delays the timing of opening and accelerates the timing of closing a little.

    It is likely to increase the velocity of the intake flow, but not the total volume of intake air, which might be reduced, thus richening the mixture maybe.
    Last edited by PGlaves; 03-24-2014 at 02:47 PM.
    Paul Glaves - "Big Bend", Texas U.S.A
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  3. #3
    aapasquale
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    Quote Originally Posted by PGlaves View Post
    Valves a little looser to what?

    Down by 4 mpg to what?

    Looser valves does two things - it decreases total lift and open cross section, and delays the timing of opening and accelerates the timing oc closing a little.

    It is likely to increase the velocity of the intake flow, but not the total volume of intake air, which might be reduced, thus richening the mixture maybe.
    down from 42 to about 38 miles per gallon

  4. #4
    aapasquale
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    Hi Roger-- haven't changed anything with regard to coding plug, so it, more than likely, is the original... I have been riding in very cold weather
    ( around 25 degrees) and have been keeping rpm in 3000-3500 range generally. Nice to be able to ride around town in 1st gear at 2500-3000 rpm without the feeling I'm going to be thrown off by a bucking bronco.

  5. #5
    Registered User lkchris's Avatar
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    If your mileage readings were sequential tanks, it would be interesting. If the higher tank was last summer, climate and seasonal fuel blends would apply. Lots of other ride parameters, too.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

  6. #6
    aapasquale
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    Quote Originally Posted by lkchris View Post
    If your mileage readings were sequential tanks, it would be interesting. If the higher tank was last summer, climate and seasonal fuel blends would apply. Lots of other ride parameters, too.
    I've gone through 2 tanks since having done the valves. Mileage has been consistent between tanks.

  7. #7
    Registered User ratze's Avatar
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    Thanks paul, excellent. on the last week of my rt resto i rode around without the tupperware, 2 modified vacum guages and AFR guage posted up on the tank. valve cover bolts hand tightened so i could make adjustments along the way, (hard to find a clean spot with no wind). but very suprised with every valve lash adjustment how much it affected air flo. happy to say its evenly balanced and running like a champ, it really pays to spend a good bit of time with your valve adjustments. fuel mileage is right at 50 loaded, dono how that happened. and i use the dobeck fuel managment setup, (1031) with no 02 sencor.
    The pursuit of reality at all cost.

  8. #8
    aapasquale
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    Quote Originally Posted by PGlaves View Post
    Valves a little looser to what?

    Down by 4 mpg to what?

    Looser valves does two things - it decreases total lift and open cross section, and delays the timing of opening and accelerates the timing of closing a little.

    It is likely to increase the velocity of the intake flow, but not the total volume of intake air, which might be reduced, thus richening the mixture maybe.
    Hi Paul, Reread your post and realized that I had only given you 1/2 an answer. The difference was the first time (last year) I did the valves they were really tight, but was still able to pull the normal feelers through. This time the feelers did not fall out, but the resistance was much less. I think I may go back in and tighten them up again and see if the mileage changes again.

  9. #9
    Registered User roger 04 rt's Avatar
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    Quote Originally Posted by aapasquale View Post
    Last week I adjusted the valves and did a throttle sync and was very deliberate and careful about setting the valves a little looser than my last bout with the valves. My bike's engine has never run better for me...very smooth, good low end torque, and not even a hint of surging. The mileage is down about 4 miles per gallon and I was wondering if the more open valves would be inclined to do that. (by the way, my bike is a 1994 R1100RS, now with just under 50,000 miles on it)
    Thanks,
    Tony
    (I've just finished the major service myself)
    Sounds like you did a good job. None of your changes should have effected gas mileage.

    If your bike is running better, maybe you're accelerating more and having a better time riding.

    What Coding Plug do you run?
    Last edited by roger 04 rt; 03-24-2014 at 02:38 PM.

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