Re: Hooooooray I found the air leak!
All carburetor installations are subject to air leaks in the slots cast into the carb throat where it tightens against the intake manifild. Using an 'O' ring in the carb doesn't assure that you're getting a good, airtight seal there. Those slots can extend past the 'O' ring seating area allowing an air leak. This is why we recommend a sealant such as a product called SealAll to assure a good seal. Silicone based sealers, for the most part, are not gasoline resistant and over time will be attacked by the gasoline, soften and allow air to pass. Read the package of any sealer/gasket maker product and most will say, 'Not compatible with gasoline" . They will work but only temporarily.
A majority of lean/fast idle conditions can be traced to air leaks in the intake manifold/carburetor/cylinder area. Crankshaft seals are also notorious for causing this condition but the intake system is more commonly the culprit.
Other causes have been found such as defective carburetors, cracks in the welds on the intake manifold and defective intake to cylinder gaskets.
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