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Thread: gas mileage/setting valves

  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
    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.

  4. #4
    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

  5. #5
    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.

  6. #6
    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
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    '12 R1200RT, '02 R1100S, '84 R80G/S

  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
    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.

  10. #10
    Registered User dieselyoda's Avatar
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    When setting valves, I use the "look" method.

    Generally speaking, there isn't a gasoline engine made that is sensitive to valve adjustment +/- 0.001". In my experience with gasoline engines, the "feel" of feeler gauge is deceptive. The springs are too light and the contact area is very narrow. What's tight to some is loose to others.

    The only accurate method of determining proper valve clearance that I know of is by using the timing/overlap method. It requires knowing the exact position of the piston and crankshaft angle. It's very time and tool intensive and takes practice. On some engines that I work on routinely, it takes me over an hour to set the valves on any individual cylinder.

    For these little girls, I put my feeler gauge in, tighten the adjuster until I can see the spring compress a bit, back it off, try again with less force. If I can slide the feeler gauge out without deflection from the spring, I'm damn close to spec. I know a guy that sets his torque wrench to 4"/lbs and calls it a day.

    If you want to really get into a mess, you need to make sure that the valve train is in good condition. That means you can't have case hardening drop outs or dished out valve stems or push rod tubes that are coming apart. Throw a flat lifter roller in, the mess get's bad, fast.

    A good valve set is an art. Art takes practice.
    1997 R1100RT (Restored Basket Case) , 1981 KZ 440 LTD (Restored Basket Case)
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  11. #11
    aapasquale
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    Quote Originally Posted by dieselyoda View Post
    Generally speaking, there isn't a gasoline engine made that is sensitive to valve adjustment +/- 0.001". In my experience with gasoline engines, the "feel" of feeler gauge is deceptive. The springs are too light and the contact area is very narrow. What's tight to some is loose to others.

    The only accurate method of determining proper valve clearance that I know of is by using the timing/overlap method. It requires knowing the exact position of the piston and crankshaft angle. It's very time and tool intensive and takes practice. On some engines that I work on routinely, it takes me over an hour to set the valves on any individual cylinder.

    For these little girls, I put my feeler gauge in, tighten the adjuster until I can see the spring compress a bit, back it off, try again with less force. If I can slide the feeler gauge out without deflection from the spring, I'm damn close to spec. I know a guy that sets his torque wrench to 4"/lbs and calls it a day.

    If you want to really get into a mess, you need to make sure that the valve train is in good condition. That means you can't have case hardening drop outs or dished out valve stems or push rod tubes that are coming apart. Throw a flat lifter roller in, the mess get's bad, fast.

    A good valve set is an art. Art takes practice.
    I guess at my stage of experience, it's time to do this more often. Once a year is not enough!

  12. #12
    Pepperfool GSAddict's Avatar
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    Not sure if you are already doing this but the valve adjust should be done with 4 feeler gauges for best/superior results.
    Also adjustments are based on mileage interval. (6000mi/10,000km)
    Typically I have found once the valves are adjusted properly, they rarely need to be touched at the intervals, just checked.
    '
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  13. #13
    Registered User leehopp's Avatar
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    More exact measure of clearance?

    I wonder if an electronic gizmo has been invented to measure the pressure in the gap. Something like a feeler gauge but with a digital readout. It seems this might lead to more exact & even setting of valve lash.

    Background: in the 3 years and 50K mi I have owned the bike I have set valves & throttle bodies many times, but only one time was magical: the bike ran super smooth with good power at takeoff and almost no surging for 4-5 months. I have never been able to completely duplicate the magic tuneup!

    My source has been ADVrider's Hall of Wisdom, Valve Adjustment for Dummies.
    http://www.advrider.com/Wisdom/OVADv2.2.pdf
    Lee
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    '03 R1150RT, 96K mi

  14. #14
    Pepperfool GSAddict's Avatar
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    Quote Originally Posted by leehopp View Post
    I wonder if an electronic gizmo has been invented to measure the pressure in the gap. Something like a feeler gauge but with a digital readout. It seems this might lead to more exact & even setting of valve lash.

    Background: in the 3 years and 50K mi I have owned the bike I have set valves & throttle bodies many times, but only one time was magical: the bike ran super smooth with good power at takeoff and almost no surging for 4-5 months. I have never been able to completely duplicate the magic tuneup!

    My source has been ADVrider's Hall of Wisdom, Valve Adjustment for Dummies.
    http://www.advrider.com/Wisdom/OVADv2.2.pdf
    No need IMO, I use a 4" feeler gauge on each valve and adjust so they just hold horizontally without dropping.
    They will have the same feel dragging back and forth
    What is most important is that they are both the same in each case.
    '
    Ufda happens..........

    It's all about the details.

  15. #15
    Registered User ratze's Avatar
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    All 4 feeler guages in and the same drag on each one, and hell yes, on one of my test rides i had the majical tune thing goen on. ying an yang, all the stars lined up. man did it run good, still trying to get it back. iam close, but dammit man. maybe one day.
    The pursuit of reality at all cost.

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