Small Engines (Lawn Mowers, etc.): kohler 25 hp v twin, craftsman lawn tractor, fuel air mixture

Question
i own a craftsman lawn tractor model # 944.605080 with a 25 h.p. kohler engine model# cv730 type #0029 with approx 100 hrs running time on it.while mowing the lawn this past summer it suddenly without any warning began billowing a large plume of acrid white smoke i immediately shut the engine down and opened the hood after a few minutes i realized that oil was leaking from the air cleaner onto the muffler it would seem that oil is being drawn into the carb through the breather tube from the valve cover breather in such quantity that it is over-whelming the carb. i ordered and installed a replacement breather kit from sears but the problem persists. there doesn't seem to be any other issues the machine runs fine other wise as long as i keep adding oil to the crank case before use (about 1/2 liter). there is no undue noise or change in rpm it doesn't blow any smoke from the muffler. just every 20 to 30 minutes of operation a large white plume. any solutions you can suggest would be greatly appreciated.

thanks in advance

steve

Answer
Steve  

For the most part, smoking is just as bad for a small engine as it is for you. Excessive smoke from the engine may be an indication of problems with the carburetor, rings, or gasoline:

   * Black smoke is a symptom of an overly rich fuel-air mixture. This could be caused by a choke that is partially closed, a faulty carburetor, or the need for a carburetor adjustment. Make sure the choke if fully open. See the sections on carburetor adjustment and carburetor cleaning.

   * White or black smoke may also result from yard debris, oil, or other contaminants on the exterior of the cylinder as the temperature after a few minutes of operation will reach several hundred degrees F even with proper cooling. Stop the engine and let it cool for a few minutes. Then, check around the cylinder, cylinder head, and under the shroud for grass clippings, leaves, oil or other spills, dead rodents, etc.

   * 2 stroke engines will always produce some fine white/blue smoke since the lubricating oil in the fuel mixture is being burnt along with the gasoline. However, excessive white/blue smoke could indicate an incorrect ratio of gasoline to oil or a mixture which has been sitting around for a while - the more volatile gasoline evaporates leaving behind the oil. It could also be an indication of contaminated fuel.

   * 4 stroke engines should produce virtually no smoke while running. At first startup of the season, there may be a few seconds of white/blue smoke resulting from the oil squirted into the cylinder at the end of last season (you did the preventive maintenance, right?) burning off as well as white smoke/steam from accumulated moisture. If you tip the mower on its side routinely (to clean out grass clippings, for example), oil may seep into the cylinder resulting in white/blue smoke at startup as well.

     White or blue smoke while running may be an indication of an excessively worn cylinder or rings or a clogged or inoperative breather (the breather assures that there is always negative pressure in the crankcase - if not, oil can get forced up into the cylinder). Or, you may be using the fuel mixture for your 2 stroke weed whacker by mistake!