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BradW

Oil Breather Bad?

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BradW
I am in the downhill run here just about to start to put this Briggs 8 HP back in my Broadmoor. After repainting everything and changing all the bad bushings on the tractor. BUT,, before I took apart the tractor and took out the engine I noticed that I am getting a little oil leaking out the oil breather tube that goes to the carb intake. Does someone know or think that the oil breather might be bad. And should I change it.The engine did smoke just a puff every now and then but not very much. Otherwise this engine runs very good( no back fire or any other problems). And where has Jack been? I've not seen him on here for awhile. Thanks in advance, KS

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-- from David A. Sohn 9/14/2000 Saint Louis Missouri david.a.sohn@juno.com The breather assemblies and PCV valves are often ignored to the detriment of the engine. The breather's filter element will decay as years pass-- if integrated into a one-piece breather assembly, you must replace the entire breather assembly about every 10 years. My guess is that a PCV valve should be replaced a bit more frequently than that. Be aware that some breather assemblies (Tecumseh and Briggs and Stratton in particular) have a flimsy plastic flap that goes bad also. When breathers and their flap mechanisms get plugged with dirt, or deteriorate and function badly-- then the engine can consume large quantities of oil, due to an overly pressurized crankcase. Crankcase gaskets (e.g. "side plate" or sump gaskets) also can be blown out due to crankcase pressurization. Also, when the breather needs replacement or servicing-- then dusty air from outside the engine can be admitted into the crankcase oil. And any extra dirt in the engine oil damages the engine vigorously. Something else necessary at 10- year intervals: It is vital to change out connecting rods every 10 years to save your engine from destruction. If this engine has been apart for rebuilding, be aware that there are rebuilds that are done right and wrong. Particularly, re-use of the original connecting rod must be avoided. If it was re-used, your engine is in mortal danger of receiving a thrown rod and a big window put through the block-- this ruins a good engine. This can occur at any operating speed, no matter whether the engine is under load or not. All aluminum- alloy connecting rods will break eventually given the stresses they endure. It is amazing they last even a few years-- considering the extreme temperatures, aluminum alloy construction, splash lubrication system over pressurized system, etc. Accordingly, when my engines are down, out of the machine, I rebuild them-- including crankshaft crankpin turned undersized if warranted, and a New Connecting Rod of original or undersize as needed. I also have the cylinder bored and use oversize piston as warranted. Leaving an old crankpin with "out- of- round" wear on it-- and an ancient connecting rod slapping around the crankpin-- is an extreme invitation for trouble. I would strongly urge disassembly, have the crankpin measured for wear, and if needed have a machinist "turn" it down to "first cleanup" of undersize based on available undersize connecting rod from your parts distributor. Usually they are available in .010, .020 or .030 undersize-- but VERY Important to ask first what they can supply you. Technically, a ".010 Undersize Connecting Rod" is constructed at the factory with the dimensions necessary for a proper fit to a crankshaft crankpin that has been properly "turned down" .010 undersize from the original factory specification for the crankpin. The machinist must first understand the original factory crankpin diameter-- in order to know how much metal to shave off the crankpin to achieve the desired effect-- and proper fit to an Undersize connecting rod. Also, measure the cylinder and see if it should be turned oversize to first cleanup to available oversize piston-- usually .010, .020 or .030 oversize. NEVER give the machinist a piston to use to guide himself in boring out your cylinder oversize. If you do, he likely will ruin your engine, because in haste, he may erroneously use water- cooled standards and make the clearances too tight for an air- cooled engine. Your engine will run maybe a minute or three and lock up tight. The air- cooled engines use far larger tolerances between piston and cylinder because of far higher temperatures in the air- cooled engine. So-- instead, just tell the machinist what the original bore size was exactly-- and ask him to bore and hone the cylinder to "first cleanup" to .010, .020, or .030 oversize according to piston availability from your parts distributor. You should be aware that a Briggs and Stratton service book is essential in repairing your engine-- it does have a few peculiarities and worth the $15 investment. Valve Work. Remove, inspect, clean, and lap the intake and exhaust valves per service manual. Clean out any varnish from valve guides and valve stems. Renew valve(s) if lapping does not produce the desired appearance. Remove absolutely every molecule of lapping compound from all engine surfaces-- otherwise your engine will be vigorously destroyed. Remember to set the valve clearances per the service manual. Reassemble. For minimum valve- guide varnish buildup, use 93 Octane fuel without ethanol-- and use Pennzoil 30W in summer and Pennzoil 10w30 in winter for zone 5. Change oil every 20 hours or more frequently in dusty or winter conditions. About Runnability. These tips often help runnability: Be aware that many of the newer fuels are lousy for use in Air- cooled small engines. Many new fuels cause "detonation" effects-- that stresses the engine terribly and shortens its life. Several fuels burn so slowly that the fuel is still burning when it enters the muffler-- this circumstance overheats your muffler; causes reduced power; and can cause backfiring. Cheap, Low octane fuels also may encourage varnish buildup in your carburetor-- and carbon buildup on your valve stems and in combustion chamber. To get around those dilemmas try these ideas: Use the high octane fuels that pass the BMW valve- stem buildup test across 100,000 miles with virtually No valve- stem buildups. Use 93 Octane fuel; AVOID Ethanol- tainted fuel. (I use Amoco 93 Octane). Remove carbon every 100 hours. Ensure proper ignition operation and timing. Ensure your tractor gas tank, Fuel filter; and Fuel line is free of contaminants. Keep carburetor clean and properly adjusted. Store gasoline properly in airtight container. Never use old gas. Store your engine properly if to sit more than a month-- including siphoning out old gas then running engine till dies from lack of fuel in carburetor. Change Oil every 20 hours (or MORE frequent-- especially during cold weather or more dusty environments). Use 30 Wt. Pennzoil summertime; and 10W-30 Pennzoil wintertime. Ensure proper air filter maintenance. On Kohler K- Series engines, frequently clean and Oil (30 Wt) the foam prefilter around the airfilter. Ensure No Dirt is Bypassing the Air Filter. Use of Heavy Grease on the air filter lip may help prevent dirt bypass. Change the paper air filter frequently. On engines with all-foam air cleaner, frequently clean them, dry them properly-- and most important: Oil them thoroughly (3+ tablespoons 30 Wt). Work the oil through the entire filter, and wring out excess. It is the oil that "traps" the dirt going through an all-foam filter. So-- Lack of oil in the foam air filter makes the filter basically useless and lets the dirt go right on into the engine and damage it. All cooling- related components should be inspected, and cleaned annually (or more frequently under dusty conditions) using the proper service procedures. Check for and clean out clogged cooling fins; clogged fan blades on the flywheel; and ensure the blower housing and heat- carrying sheet metal is properly assembled. I hope this helps some. David A. Sohn

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