Carburetor Problems

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Posted by Tom S. on May 25, 2018 at 17:37:13 [URL] [DELETE] :

I have a 49 8N, and I have two carbs I've been switching back and forth because neither seems to work right. For the past month or so I've been using a M/S knockoff, which was working fine until I neglected to turn off the gas when I shut the tractor down one night and, when I went to start it, wound up with a crankcase full of gas. (I did a class A oil change afterwards.)

Since then, the tractor won't start when it's cold using the M/S carb - instead it floods out almost immediately and I end up with maybe a half cup of gas trapped in the connector to the air filter. (And I do shut off the gas now religiously - lesson learned!) However, when I switch to the old Zenith carb, the tractor starts fine but runs poorly - not much torque, stalls out easily, and moving the throttle doesn't vary the engine speed a lot (I suspect the idle is set too high).

Yesterday I got the tractor going using the Zenith carb, ran it for awhile, and switched out to the M/S. It started right away and ran beautifully - nice low idle speed, power when I was climbing a slope (I think the governor was doing its job, which it doesn't seem to do with the Zenith). I worked it for half an hour or so, shut it down, and when I tried it again a couple of hours later it started right up and ran well. But this morning, with the M/S carb still attached, it flooded out and I got lots of gas in the air intake pipe again. I switched back to the Zenith. It started and, again, ran okay but not great.

So, my questions: 1.) Should I have that much gas in the air pipe after only cranking it for less than a minute? (I get that with the M/S but not the Zenith). 2.) Why does the M/S work well when the tractor is running, but gives me headaches about starting? 3.) What might be up with the Zenith? It's a pretty old carb, whereas the M/S is almost new?

Sorry for all the text. Thanks.

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