My 27 had a fuel leak since I bought it 3 weeks ago. The bowl over-flows in 20 min after engine is shut off. I have serviced the float valve with new needle jet, brass insert and ring gasket and set the float level to the quarter inch spec. This overflows with the fuel shut off or not but the fact is I can't get this float valve to close and seal. Float has no leaks. I've ordered a shut off that mounts at the fuel input on the bowl to stop the fuel there... but it still bugs me why the jet wont seal. Any thoughts? Jeff
Try setting the float from 5 to 7 1/16ths. First make sure nothing is binding up. KGB
All the new ones leak. The vendors have been told about it for years and continue to sell them. Many people have better luck with the needle and seat sets from Chaffins than the ones sold by other vendors. If you have a small lathe or drill press you MAY be able to smooth the ridges off the needle and get a smooth finish that will seal.
Also, if you look back through the forum 2016 and search for NH carbs you may be able to find a lot of information including a post from me about making a lead gasket instead of the hard one the vendors supply that is too hard to seal against the rusted cast iron seat boss.
I have set up to make my own needles but don't have time or the capacity to provide them for other users. About the best you can do with a new one is re-grind that tip. The best is if you can find a new old stock one or try one with the Viton tip instead of steel.
Most NH, Holly and Kingstons will leak also sooner or later and that is why the peddlers make that nice brass valve to shut off the gas. One of my vap's leaked for years and had to have the gas shut off when parked, about a year ago it stopped leaking and never has leaked again.