Breather 101

[bob]

I have a Gardenway/Troybuilt rototiller with Tecumseth 6HP flat head engine. I do not understand how the breather works. All the breathers I have worked on have a breather tube that comes out and points straight down. This one comes out and connects to intake just below air filter. How does that works without sucking oil into the carb. Right now I have the engine running good at times and then all of sudden it will start smoking. I have taken the breather out and am cleaning now. I know oil seepage hole goes down which looks correct. What else am i looking for. Thanks

Blair

[bob]

Forgot to mention I was running engine with breather tube disconnected from intake and thats when I noticed oil shooting out. I then connected and then the intermittent smoking started

[RoyM]

That indicates either a faulty breather which is not likely or excessive blowby from a worn engine. That H60 is an old timer with probably lots of hours on it. Are you the original owner? The hose is connected to the breather because of the EPA, keeps the engine from poking a hole in the ozone layer.

[creia]

Bob,
While the breather tube orientation you describe was not that common in Tecumsehs, it was VERY common on the old Briggs flatheads that used the "Pulsa -Jet" carb, and actually works very well. Something is not right (possibly some of the causes pointed out by RoyM). You should not see any OIL coming out of the breather, as it is supposed to only vent crankcase air/fumes.
Michael

[bgsengine]

I have a Gardenway/Troybuilt rototiller with Tecumseth 6HP flat head engine. I do not understand how the breather works. All the breathers I have worked on have a breather tube that comes out and points straight down. This one comes out and connects to intake just below air filter. How does that works without sucking oil into the carb. Right now I have the engine running good at times and then all of sudden it will start smoking. I have taken the breather out and am cleaning now. I know oil seepage hole goes down which looks correct. What else am i looking for. Thanks

Blair

Well if you want the educational explanation... Crankcase breather , well, lets the engine breathe... As the piston is moving up in the crankcase, the change in crankcase volume will create a vacuum or suction effect (which is desirable) and then as the piston moves back down, it creates PRESSURE, which is not desirable (excessive pressure can blow out gaskets and seals, etc.) crankcase breather has a check valve / flapper valve, that opens to let pressure out and closes when vacuum begins (which helps keep oil in, helps keep gaskets in place, helps keep oil seals seated, among other duties) - However when the crankcase is pushing pressure out, there will be atomized (oil vapors) in that air (which is why you may see oil coming out - a little bit of oil vapor is normal) - most of the oil is captured by a breather filter in the breather chamber , which drains down and then exits back to the crankcase through a drainback hole.

Excessive oil coming out the breather on an L-Head is generally caused by a relatively few things - the more common one is, the drain-back hole gets plugged up with oil sludge over time - sometimes just simply cleaning that out solves the problem.. It can also be caused by a failing (or failed) breather check valve (broken reed or sludge/carbon holding it open, etc) which may also be accompanied by other crankcase leaks - and lastly, can also be caused by worn piston rings - allowing excessive combustion blow-by into the crankcase - breather can't control that much added pressure.. Breathers can fail the other way too and fail to open allowing excess crankcase pressures to build up which can blow out gaskets and pop oil seals out of their seats, even had one that kept blowing the oil dipstick out of its tube repeatedly..

In days gone by, there wasn't as much concern for the environment, so manufacturers went cheap and just vented crankcase vapors to the atmosphere.. although some would hook breather tube to air intake so as to help prevent dirty air from getting into the crankcase.. and of course the EPA steps in and then all engines had to have breather vented to the air intake (just like cars with their PCV valves had to hook to air filter housing)..

In an OHV engine, there's a new dimension added with possibly blown head gaskets that leak combustion to the crankcase via the pushrod galley - that can pump a whole lot of oil into the air intake in a hurry..

If your engine is operating normally and not using excessive oil, then you'll want to hook that breather tube back up to the air intake, or you're gonna be making things worse - with that air intake open, engine's gonna suck in dirty air.. Also first thing to check when excessive oil through breather tube and into the intake is suspected, would be to try a new air filter - even if it looks clean, if paper filter got wet the cellular composition of the filter media will change and acts just like a plugged up air filter... But if you are seeing a lot of oil pumping out the breather tube on an L-Head, first thing to do would be pop the breather off and clean it and be sure the oil return hole (can be quite tiny and hard to find) in both the breather and the valve box are clear, and visually inspect breather reed or plate (Briggs engines had a round fiber plate that isn't spring loaded but would close when air flow changed, so just because it doesn't seem to be closed, doesn't mean it is bad) and might want to do a compression test , check for worn rings, and make sure the crankcase is sealed (including dipstick and tube - failures in that area can cause breather to not operate properly) , and as a last resort, replace breather.. in my 40 odd years in this business, Ive only really seen a truly failed breather perhaps 3 or 4 times... lot of failures can be blamed on breather, but it isn't the breather's fault.. the root cause was found elsewhere.

[38racing]

briggs manual shows how to check some of them and says not to touch the disk.

[KE4AVB]

There is one area not mention here about L-heads. That is exhaust valve guide wear.

I have replaced several Briggs exhaust valve guides that was causing excessive crankcase pressure. Normal back pressure from the exhaust muffler can cause blow-by in engines with excessively worn exhaust guides.

But as said it is more commonly piston blow-by that is the main culprit but the leak down test usually will confirm this; unless, it is lower cylinder problems. Sometimes the only way to verify cylinder and valve guide condition is to pull the head and have a physical look see.

Like BGS I have only replace a couple breathers (reed valves) on OHV engines and none on a L-heads. I still got the a breather assembly from 2009 still sitting in my parts bin. Its where my brother insisted it was the problem but that engine had a worn valve guide. This is how I ended up with my valve guide tools with one oversize reamer due thicker after market valve guides. Weird the only set I have used is the 1/4" set, 5/16 set is still collecting dust as is the valve guides. Oh well they are there if I ever need them.

[bluemower]

some good explanations from the others. Here is additional information that is quick, easy, and does not cost anything. When checking the engine oil, the tiller should be positioned so the engine is level. Ensure this is serviced with the correct grade and quantity of oil and that the oil is not contaminated with fuel. Too much oil will increase the oil fumes and splashing that BGS was describing. Oil containing fuel will flow through that breather filter easier

Here is a story. These were great machines. In the 1980's, troybilt advertised their tillers were so smooth, even a 90 year old grandma could operate. I was dispatched to pick up a Tecumseh powered horse tiller and the operator was a 92 year old grandma.

[SUKI]

One thing though is not to try tiller too deep until the soil is loosen. When first got my Horse it got up on the tines pull me to ground rather quickly in hard clay soil. But once things was loosen it was easily operated one handed even tilling at full depth.

[bgsengine]

BTW this past year I did two re-powers on troy bilt horse 6 HP models - both Tecumseh cast iron engines were replaced with HF Predator 6 HP - its a drop-in replacement, pretty much, except some need the crankshaft pulley bolt replaced if it is a different sized one... I did take a little care in making sure of the pulley shims to get drive pulley to line up with the input pulley - typically with the new engine, may leave out a .020 shim or so, if I recall. The predator engines these days seem rather much better than the "clones" , and I did a close-up comparison with one that had a Briggs vanguard 6 HP put in the year before - Other than the linkages (The vanguard was built in such a way that the throttle control on the handles was not needed at all.. the predators had sufficient means to hook up the old throttle control, if it was long enough) - There's almost no difference between the briggs vanguard engine and the HF Predator otherwise, other than the vanguard's 3 year warranty.. and the 3x price.. performance-wise, all three tillers performed pretty much the same - (and the new engines actually were an improvement over the worn out tecumseh cast iron ones)