Briggs Vanguard Problem

[jlemon]

Went on about a 2 mile ride in my Response yesterday. About halfway through the ride every once in a while the engine would stumble and it would get a puff of white smoke out of the exhaust. I walked around the woods a bit and when I started it back up it had no power at all. Hit the throttle and it would just bog down. I pulled the air filter cover and it was just saturated with oil and there was oil coming out of the breather tube. I started it without the cover and it was fine, no smoke and full power. The air filter was soaked in oil. It hasn't did this before and it doesn't smoke or anything. The piece in the attachment is listed as a "breather" in the Briggs engine breakdown. Is it a type of PCV valve?

[LarryW]

Went on about a 2 mile ride in my Response yesterday. About halfway through the ride every once in a while the engine would stumble and it would get a puff of white smoke out of the exhaust. I walked around the woods a bit and when I started it back up it had no power at all. Hit the throttle and it would just bog down. I pulled the air filter cover and it was just saturated with oil and there was oil coming out of the breather tube. I started it without the cover and it was fine, no smoke and full power. The air filter was soaked in oil. It hasn't did this before and it doesn't smoke or anything. The piece in the attachment is listed as a "breather" in the Briggs engine breakdown. Is it a type of PCV valve?

Where you driving up/down/sideways terrian? I assume you checked your oil level and its not over full or anything?

I have had that happen once in a Tecumseh single and it was because the piston was worn oval and it created so much back pressure it splurted oil out the breather vent on the side of block. Hopefully you have some other problem.

[racerone3]

check out this thread. i think your having the same problem

http://www.6x6world.com/forums/argo-atvs/6519-2003-bigfoot-pooring-out-white-smoke.html

[jlemon]

I read up on that thread this morning. I'll pull the breather back off again today and check the drain back hole. I did drive across a couple ditches that put it on an incline but not for very long. After cleaning up the oil I drove it a bit without the air filter and it was fine. I'll pick up a new air filter tomorrow and check it again.

[Roger S]

You guys posted before I finished this essay but since it took so long to type, I'll leave it.

I'll tell you what I think, and also ask my briggs guru. It is the crankcase ventilation, obviously. The vanguard twin and other engines that share one crank journal create a lot of pressure differential in the crankcase, due to both pistons moving up and down somewhat at the same time, rather than an opposed twin or an auto engine where the volume in the crankcase stays the same as it rotates. So the briggs doesn't have a fresh air intake to the crankcase and a pcv valve with constant vacuum on it to do crankcase ventilation.

The pics of your breather show a one way valve, and a couple of little holes on the edges. When the pistons decend, the engine "exhales", sneezing out through all three holes, mostly the big one obviously. And the hollow chamber inside allows some oil and air separation before it vents up through the hose into the air cleaner. Now, as the engine turns and the pistons rise, there's a negative pressure in the crankcase. The one way valve in the breather is shut, but the two little holes near it may allow oil from the seperator chamber to be sucked back into the crankcase where it belongs. That's how I see it..

These pressures also make the pulse fuel pump work. There is also a baffle in the crankcase that helps seperate oil and air before it gets to the breather assy. The vent ends up dumping into the air cleaner because the EPA would like to have the vent contents burned rather than dumped on the ground, like crankcase vent tubes from the 1950's. And when the vent sucks back in slightly, it needs to be filtered air. I vented mine to a remote filter and "catch can" and plugged off the air intake. Got tired of buying air filters every time I layed the argo over to the right side. Just normal hot rodding with a less than perfect ring seal will put more oil on the air filter than I like.

So after all that long winded stuff, are you ready for an answer to your problem? OK, my answer is I don't know, for sure. But you are armed with my personal ideas of how the thing works.

I'd clean the thing up, and blow through the hose nipple. The flapper valve should stay shut, and the two little drainback holes should be open. If it's working right, and still pukes oil, it makes me think the breather can't seperate oil and air adequately. Oil level very high, maybe thick oil can't drainback, worn rings.. those are my guesses. Plumbing it away from the carb is one cure, but it has to be in a container to catch the oil, 'cause it'll make a mess if you just stick a filter on the breather outlet.

[jlemon]

Thanks, that some good information. I like the idea of a catch can. I just rewatched the video right before it started doing it. We were pretty much full throttle in a wet field and spun it around in a circle a couple times. I guess that could have pushed oil up through the breather.