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  1. #1

    Join Date
    Jun 2012
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    Pasadena, MD
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    73

    How do I adjust pop off pressure?

    I hate to start a thread on this but the sites search function doesnít seem to be working for me today. Iím trying to hit the 42-45 pop off according to Bills modifications. I have 1 carb that pops at 44-45 and the other two pop off at 39-40. Did the tests 4 times each carb. 1.5 N/S 95 gram springs everything to Billís specs. The gauge is in 5 pound increments so these are my best guesses. How do I bring the 39-40 up and the 44-45 down a little? I remember seeing something about cutting the spring or stretch the spring or donít stretch the spring. Also checked with a razor and each arm appears to be sitting even. Thanks.


  2. #2
    Predator-x's Avatar
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    Sep 2012
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    Enkhuizen/Netherlands
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    135
    +1
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    I always stretch or press the springs to get the right pop-off pressure , you should never bend the spring arm.
    If you canīt get the pressure right then change the spring to a different strength.

  3. #3

    Join Date
    Jun 2012
    Location
    Pasadena, MD
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    73
    Would that be stretch for a higher pop off number and compress to lower the number? And if you stretch it will the arm not be even, will it rise up higher than it should be? Thanks.

  4. #4

    Join Date
    Jun 2011
    Location
    hopewell,Va.
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    139
    you stretch the spring to get a higher pressure and compress it to get lower. i would recommend to try and get the high reading carb down to match the other two carbs. are you running f/a's on your carbs?

  5. #5

    Join Date
    Jun 2012
    Location
    Pasadena, MD
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    73
    Stretched the two springs a little and now popping off in the 42-43 area. Compressed the other one and it’s in the same area. Yes I will be running FA’s. Used Bills instructions on Accelerator pump removal, Drilled returned pressure balancing modification and aftermarket F/A’s chokes intact, 110 Pilot jets, 1 turn out on low speed adjusters, 120 main jets, 1-1/2 turn out on high speed adjusters, 1.5 Needle and Seat, 95 gram spring (Dull Silver) 42-45 avg. pop-off pressure. Also rebuilt the carbs with Mikuni kits. Hoping to put it all back together and back on the water to see how it will run. Unfortunately it wont be until next weekend heading to Skyline Drive this weekend with the bikes. It’s been quite the project. Thanks for the help.

  6. #6
    The problem with stretch and compress is you'r changing the natural ratio of the spring, and it might just springback to where you dont want it. Its OK i guess, but my opinion is; better to not mess with a spring's tension. A couple heat cycles and you might no longer know what its doing.

    You can also very carefully clip the springs shorter. I used 115g springs to get down to 43psi because my kits only came with 115g springs. Clip only about 1/4 turn of the spring at a time and test every time. it doesnt take much at all.

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