Like many others I've been plagued with a leaking Zenith carb that has been driving me crazy trying to fix. I looked back at the numerous threads on this subject, even my own from 2017 when I had the same problem with another car. Like almost everyone else I figured it had to be the needle and seat valve. Well, it wasn't. I won't bore you with all the ***-ache I went through to get to the point where I have finally stopped the leak
In some of the threads I saw mention of a "dimple" on the float that could affect the needle valve. I checked my float but couldn't see any "dimple" so I discounted that as a possibility. That was my mistake.
After reaching my tolerance level of frustration I figured there had to be something that was preventing the needle valve from closing entirely. The only other part in the mix is the float.
With my reading glasses on, and the float held just so in the light, I could see a mark where the needle touches the float. I wouldn't call it a dimple, it was so small and insignificant. But I figured I had noting to lose by polishing it out.
Using 400 grit wet-or-dry paper I polished the surface to be as sooth as possible. I reassembled the carb and let it sit. I have a sight gauge on the carb so I can tell the fuel level. This time the level stayed where it was suppose to be. It has been over 24 hours and still good. Before, it would rise to the point of leaking within two hours.
The next time I run into this I'm going to polish the surface even higher, probably to 800 or 1000 grit. If you think about it, the needle has to skid along the surface of the float as it closes. The amount of movement is so small it wouldn't take much to interfere with smooth operation, especially considering what little pressure is exerted by the action of floating the float.
It's hard to believe how something so insignificant can cause such frustration. I hope this helps someone else avoid it.
In some of the threads I saw mention of a "dimple" on the float that could affect the needle valve. I checked my float but couldn't see any "dimple" so I discounted that as a possibility. That was my mistake.
After reaching my tolerance level of frustration I figured there had to be something that was preventing the needle valve from closing entirely. The only other part in the mix is the float.
With my reading glasses on, and the float held just so in the light, I could see a mark where the needle touches the float. I wouldn't call it a dimple, it was so small and insignificant. But I figured I had noting to lose by polishing it out.
Using 400 grit wet-or-dry paper I polished the surface to be as sooth as possible. I reassembled the carb and let it sit. I have a sight gauge on the carb so I can tell the fuel level. This time the level stayed where it was suppose to be. It has been over 24 hours and still good. Before, it would rise to the point of leaking within two hours.
The next time I run into this I'm going to polish the surface even higher, probably to 800 or 1000 grit. If you think about it, the needle has to skid along the surface of the float as it closes. The amount of movement is so small it wouldn't take much to interfere with smooth operation, especially considering what little pressure is exerted by the action of floating the float.
It's hard to believe how something so insignificant can cause such frustration. I hope this helps someone else avoid it.
