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  1. #1

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    Pop off pressure testing

    Could not seem to tune away the low end bog on my GPR. Pulled the carb bank and found that the #2 carb when running a pop off pressure test was leaking. I thought that I had found a "dribbler". Replaced the needle and seat and the leaking persist. The problem is that the leaking is around the "O" ring on the seat. Seems that it would leak fuel, but not through the needle and seat, but rather around the "O" ring.

    Keep in mind that this is a brand new Needle and Seat.

    Any one out there have a fix? Is replacing the "O" ring with a thicker one (larger outside diameter) the best option? If it is, then does anyone have a size that I can use to order some?


  2. #2
    Moderator OsideBill's Avatar
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    Salty make sure the oring is not twisted or getting shaved and also that the bore is clean and free of any corrosion or burrs. A Jewelers Loupe is a valuable tool here. I also use a little Dielectric (Silicone) grease on all orings. if it still leaks you need to enlarge your oring. I do this by cutting kapton tape in thin strips wrap a layer or two around the oring groove install the oring and check again. This is a pain to do but I have used it many times to solve issues with air cylinders and such.

  3. #3
    cheatin' piston popper addicted's Avatar
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    I noticed that the orings get flats on them too. Especially on my older ski's. I usually just steal one from another N&S and it fixes it. If you get new orings, make sure they are viton. Also, the rubber nipple cap things that the n&S come in can actually ruin the seal on the needle if they are pushed in all the way.

  4. #4

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    Smile

    Thanks for the advise guys. The "O" ring did have a flat spot. Replaced it with the one on the old N&S and pop off went back up to 40. Life is good again.

    I do not know why I sometimes make things more difficult then they have to be. Appreciate you guys reminding me to KISS (keep it simple, stupid).

  5. #5
    what size needle and seat and spring combination are you using to get a pop-off pressure of 40? Thanks

  6. #6

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    1.5 Needle & seat
    95 gram spring

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