LX188 leaking fuel out of carburetor

Oliver 77

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I found a small depression in the rubber tip of the needle valve from replacement carburetor #1, the one that worked fine for six months. The tip of the other needle looks fine. The seat is evidently not replaceable and doesn't appear to be conical. Wondering if t could touch up the seat with a drill and get a better seal. Won't be out much if it doesn't work.
 

Hammermechanicman

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If the seat is metal you can chuck a Qtip in a drill and use FINE valve lapping compound or regular toothpaste to lapp in the seat. Then clean the carb till you are sure it is clean then clean it again. The rubber tip on a lot of the chineesium carbs don't like ethanol. Take the rubber tipped needle and put it in some gas for a day or two and see if if swells or seems softer. The biggest issue i see on AM carbs is the float needle tip sewlling and getting soft. Also make sure the leak is the carb and not the fuel pump. There was an issue with some Kaw engined JD mowers where fuel pump near carb actually leaking and not the carb. Does it do it right after you shut off the engine? They also had problem of fuel boiling in carb from heat soak from very hot engine and muffler.
 
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Oliver 77

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I thought it was the fuel pump initially but after replacing it found that it was definitely the carb overflowing. It's kind of amazing that we haven't read about a bunch of these mowers catching fire as the carb overflow dumps right onto the muffler.

Thanks for the suggestion about the lapping compound. I hadn't thought of that. The seat on the original Mikuni carb is just a hole drilled in the main casting. The Chinese replacement actually looks better, with a machined brass seat pressed into the main casting.

The needle tips have been in fuel for some hours without any noticeable deformation, other than the slight depression in one that I mentioned.
 
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