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  1. #1
    1996SLTX's Avatar
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    Variations in premix ratios

    Found this excerpt on the internet....it may explain why my SLTX performs slightly different on different days. Some days the throttle response is perfect, other days there's some hesitation mid throttle....I shoot for 40:1 but I don't absolutely positively measure with total precision. I pump in 10 gallons and then eye ball one quart from my gallon jug looking at the scale on the side of the jug. Other factors would be humidity and temperature, but down here it's always humid and warm in the summer.

    "If you richen the pre-mix ratio (20:1 as opposed to 30:1) there is more oil and less fuel in the same volume of liquid, which effectively leans the air-fuel ratio. And this fact gives the clever tuner one more tool to use when the correct jet is not available or when none of the standard jets are exactly right. You can richen the jetting by slightly reducing the pre-mix ratio (less oil). You can lean the jetting by increasing the pre-mix ratio (more oil). The best part is that changes in the pre-mix ratio affect the jetting over the entire throttle-opening range, but the changes in ratio must be small to prevent excess wear from lack of lubricating oil or fouled plugs from too much oil. "


  2. #2
    Moderator beerdart's Avatar
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    A must have tool. My pistons love me for it. (Well most of them)

  3. #3
    www.springbreak-florida.com rgard32's Avatar
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    i do the same thing..i just eyeball a quart container at the gas pump...but i see no variation in the way it runs..BUT mines a 785 pro too

  4. #4
    1996SLTX's Avatar
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    Cool, I'll get one...I'm pretty dang close. I was using an empty quart bottle to measure with since I usually pump 10 gallons into the tank to make it easy to know how much oil to mix. 10 gallons is what we usually use in an outing.

  5. #5
    ph2ocraft's Avatar
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    Ive never actually "felt" a difference but I do lose roughly 40RPM's mixing 32:1 versus 40:1 but nothing beats 40:1 on a brisk morning and an easy 100RPM gain. So many factors.........

  6. #6
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
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    I have a plastic measuring jar made with all the ratios,what's great about it is it has a lid that screws on,so no mess or dirt inside.cost 4 bucks from my parts place.

  7. #7
    FLjoyrider's Avatar
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    I got one for $2.25 at wal mart and its got a big opening and a lid, and every mixture scale you can think of so its real easy to pour and measure from my 2.5 gal. oil jugs.

  8. #8
    Quote Originally Posted by Keddano View Post
    I have a plastic measuring jar made with all the ratios,what's great about it is it has a lid that screws on,so no mess or dirt inside.cost 4 bucks from my parts place.
    I found that one also! it makes the ratio rite look like a joke because the lid actually works and they were smart enough to include 40 to 1 for up to 8 gallons Ratio wrong doesn't even have 40 to1 for 5 gallons even though it would have fit plus with the bottle you can load it for the ski if your going to refuel at the marina

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