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finally found out how to post a thread/float needle vs petcock

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  • finally found out how to post a thread/float needle vs petcock

    ok first off i thought for a bit there that this forum was so elitist that i had to pay the subscription fee (might anyway because i feel bad for having adblocker and it not even realizing and it's only $20 for a year, unlikely to even use this site that long so basically forever in my books, anyways the other thing i wanted to address was leaky carb float valves, so if the petcock fails people often have their carbs flood and gas fill their crankcase or airbox, and there was a thread earlier where everyone said that should not happen, well i personally have a brand new oem petcock for my bike but will switch to prime for testing purposes, now i have my reasoning to make me believe that with a full tank you will have some though minor leakage if full flow for that leak is allowed from the petcock, but i will try everything in my power to stop that for these test i will be doing, also i can set my carbs under the bike with tank pressure, totaling a whopping ~33 inches or almost 3 feet or 84 cm, that is 1.2 psi, not much since i test at like 10 psi, but continuous pressure is different than a 30sec-3min leak test, simply put most of our leak testing equipment has leaks equal to or greater than that of the carburetors, what i will be doing for the sake of testing is buying 4 new oem Keihin (my carb brand) float needles (6 actually) and testing one carb that failed a standard leak down test even after several stages of cleaning and a stage of polishing of the seat, this time with the 4 new valves i will be polishing the seat several times and with multiple styles of polishing, making sure to get down to the sealing surface where the needle actually seats, then i will install the new needles, if this carb still fails pressure testing after readjusting the floats and i get as low as 10 psi and still have failure, i will put these needles in the carb that i tested at ~20 psi and retest, also with extra seat polishing, it should then seal better and i might bump my test to 30 psi, after a standard leak down test i will do a real fuel test with the carbs below the bike, now please note my carbs do not have overflows and the only hoses going to the bowls are the vent hoses way above the jet openings and intake, so any leakage will be to the engine side or air box side, of course i have the carbs off so if there are any leaks they will drip outside for me to fully see and measure (read count, because if i could find a tray to put under the carbs that would be great but i doubt it will happen) if after all that i will have verified (unless polishing is not good enough for my seats and they are trashed, or i get crappy needles because they are from ebay) that carbs on a vacuum petcock type bike will leak if in the prime position or if your petcock is leaking, i wish i could answer this 100% without a doubt but all i can do is certify they should not leak or strongly lean towards saying they should (though small amounts that will evaporate mostly and not cause any lockup when starting for any that did not evaporate, now that is not to say that if left for several days or even months it will not cause lockup or gas soaked oil) if i had a type with replaceable seats or a way to replace these pressed in ones (can't even find them for sale) then i could know for a fact one way or the other because i would buy from the manufacture and if they did not seal i would request a refund on the affected carb(s) till they either stopped leaking or till the manufacture stopped accepting my returns

  • #2
    I'm a freakin idiot/i learned several things today

    first off i can't confirm or disprove my theory till i get more parts which means more money (or make a solution that may bite me in my backside later) so since i did my first carb set without a hitch i guess i got a little cocky or something like that because i forgot to do a few things i did on my first one, remove fuel mixture screw (seems clean and has welch plug still so i would rather use the factory (or last pro to use a welch plug) settings and not do my own tuning till the rest of the bike is tip top) i also forgot to test the floats to make sure they don't leak down (again seems fine but it would be a nice thing to do) and the last thing i forgot to do which brings me to my second item which is that i forgot to check my bowl gaskets/o-rings, i made sure the bowls did not leak but did nothing to make sure the carbs didn't leak at the bowls, and seeing as the factory fuel height is like 1-2mm above the seam i have that much fuel leaking every time i switch back to the on or reserve position (not running the bike) now this is only 2 of 4 carbs i'm checking but they both seem to leak so i better test (with water though i don't recommend) the other two if all 4 leak i need to get new gaskets i guess, otherwise i might use silicone but that's a bad idea for a cheap solution


    • #3
      wow, now i lost 2 parts, not too small i might add, i've looked everywhere, and i even had a special box that i put a cardboard base in so things won't get lost, well i'm stumped, comment if you want to know what the parts were, i't pretty embarrassing


      • #4
        I'd offer more in my reply, but I gave up reading after my second attempt. Mentally breaking the top post into sentences was too much for my Dyslexic/ADD brain


        • #5
          Slow down bro ! Help us to understand you.
          Here is your word of the day:
          "Concise" -

          One step and a time buddy.
          Your float needles should not leak on prime and you should be able to find new ones very easily.
          What are the details of your bike ? 600cc or 750cc and year ?
          My Katana-1100 17" wheel swap