john deere lx-188 17hp kawasaki liquid cooled

George5155December 24, 2013

Engine runs smooth without air cleaner housing and element.
Fitted new element, plugs, coils and cleaned carb.
Once I fit the air cleaner element and housing, the engine would not rev properly, runs smokey and uneven as if the choke is activated, which is not the case.
Can anyone please give me some advice as where to start looking for the possible problem?

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I just had a B&S do the same thing and found the crankcase oil was diluted w/ gas. The slight vacuum created w/ the air filter on was enough to pull the gas/oil mix thru the crankcase vent.

    Bookmark   December 24, 2013 at 9:23AM
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If......gasoline is in the crankcase, it's not that a vacuum is created when the air filter is in place drawing out the gas/oil mix.
Gasoline in the lube oil begins to vaporize out of the oil ( as soon as the piston and cylinder begin to warm, which is almost instantly upon start up) and creates its own specific pressure as it does so. This specific pressure will vent of its own volition without any partial vacuum being applied.
What is actually happening is that when the air filter is installed, is that the venting gasoline vapors are confined inside the confined space created by the air filter and since the gases are coming out of the crankcase vent under pressure..........mostly what enters the carb is a fuel rich mixture with very little air because with a pressure fed source inside the air filter, there is no way for sufficient air to be drawn through the filter media to make a proper air/fuel ratio.
Another phenomenon that may plague engine air filters during cold ambient air temps is air filter icing.
In humid conditions with ambient air temps near or below the freezing point of water, ice can form on the filter media and cause drastic clogging. This is why most engine driven snow blowers/throwers do not feature an air filter. Both the fine mist of snow particles and the high water vapor content (from snow contacting engine and exhaust surfaces) produce conditions which are perfect for air filter icing.

    Bookmark   December 24, 2013 at 1:50PM
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Are you using oil on the precleaner? Had you had this problem in past years? Knowing the engine, but not really in a snow environment (if that what is happening) , may just be time for a good old fashioned carb service. Start of a leaking needle maybe. The carb bowl vent one wouldn't think would be frozen itself due to the location, but check it out first. It will exit the right top of the carb under the shrouding. These have distinctly different carbs your life would be easier to look for the stamping # for parts should you pull and service it. New gaskets too when it goes back on.

    Bookmark   December 24, 2013 at 3:50PM
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