View Full Version : amt 622 leaking fuel out the carb.

06-06-2012, 06:00 PM
so my 622 leaks fuel out of the carb where the air filter attaches. it does this while it is running. I have had the carb apart and tested the needle valve and float by blowing air by mouth into the fuel supply side of the carb. the needle valve stops the air when the float is up. Any thoughts?

I am also in the process of rebuilding the fuel pump(i got a kit that has gaskets, the two rubber nubs and some plastic diaphram deals. question here is can i replace the original rubber(the one on the engine vaccum side) diaphram with the plastic one in the rebuild kit or will it only work with a rubber one?

I have had this AMT since 1996, got it(free) from a lady at the local Co-Op who lived on the back side of our ranch and she saw my grandpa buzzing around in his that we got him after his knee surgey. I completely rebuilt the motor about a year after I got it. we moved in 1998 and it sat in the back yard for a couple of years until I started it agaim, and then it sat until march when I pulled it out, built a new dump bed for it(the old one was rusted out) and have been working on getting it running again to give to my father inlaw to drive down to his pond to feed his fish.

looking foward to getting it revived again. I'll get some pictures.

06-07-2012, 01:41 AM
Welcome to the forum! Sorry, I'm not sure I can answer your questions, but that won't stop me from trying. :BG:

Guess on the float is that it is either binding (so it only seals the fuel off when you pull it hard enough) or possibly it has a hole? Either of these would probably make you run rich though. So when you say leaks where the air filter attaches, what is the "leak" like? Fuel spray back into the air box? Liquid coming back somewhere? If the former, I'm surprised you don't get back fires that blow the air filter apart. :hsu: If the latter, maybe you have a crack that the pressurized fuel is enough to breach, but not your mouth? All just speculation though.

On the fuel pump, I would think the plastic would work fine. Again just a guess, but I can't imagine it working in some applications but not others (as long as it fits your pump).

Best of luck and hopefully you get somebody with real knowledge on the subject to set me straight :lol: soon.

- Steve in CO

06-07-2012, 04:13 PM
thanks for responding.

well I picked up a backup replacement plastic pump for $20 incase the plastic sheets from the rebuild kit dont work. I did find the rubber diaphram replacement for 8.95 plus shipping. I talked with a small engine repair guy on the matter of the raw fuel pouring out the carb and he thinks the float level isn't set right or the float has a crack in it and doesnt float well. I will pull the carb tonight and float check it and make sure it is set correctly.

I may be become the knowledge guy on the AMTs... hopefully I am not the only person...haha

07-03-2012, 02:11 PM
well i got it figured out. the old fuel filter had decayed and paper element(very fine) got sucked into the needle valve not allowing the fuel to atomize making it dump out raw. its running better than it ever has now. I am starting to convert the brakes from cable calipers to hydraulics