blowing larg amount of oil out crank case breather of 400EX?

[jensenracing77]

this is more of a trivia question for the more experienced. i just wanted to get a feel for people here. this is more oil than from blow by of a worn out engine. i'm not baiting anyone just want to see what kind of experience there is here.

[rubbersdown]

sooooo this is not a real problem?
Most times it would be warn rings, broken rings, cylinder out of round etc etc. Sense you said your rings arent warn im assuming you checked and measured clearances? If so then id check for a clogged or collapsed oil return line. Oil builds up in the case because it cant make it back to the tank and thus pukes all out the vent.

[f419sr1]

Could have also leaned out and popped a hole in a piston. On going problem or some thing that just started happening?

[honda400ex2003]

it would most likely be blow by imo from rings being bad or the cylinder being out of round. pretty much all of the reasons rubbers gave. steve

[jensenracing77]

more hints. like i said, this is for people that have ben around these engines. not many have ever seen this. it is a broblem that i had only one time and know of happening 3 other times to other people and one time from the factory.

the engine runs as good as new. and most likely was just rebuilt. it can happen to one that was not just rebuilt but less common.

[honda400ex2003]

too much oil from an over active oil pump could contribute to some problem also. there are numerous things that can cause oil to blow out. over filling can also contribute but is not real likely since it is a dry sump. timing could be off a tooth but it wouldnt run right. lots of other stuff too ill keep putting them down as i think of some more. steve

[rubbersdown]

Ahhhh so its a rare 400ex only thing? I have only personally rebuilt 4 of these motors so I probably wouldnt have a clue if its particular to the 400ex but ill probably keep guessing anyways lol. Im a dirt bike guy, the 400ex I own is my wifes and ive actually never even ridden it lol.

[jensenracing77]

sorry, yes 400EX only problem

[bherriman]

At first I was going to guess Improper ring end gap / rings didn't seat because of poor cylinder honing/conditon, but you say its a 400ex only problem which leads me away from anything piston related because every bike that would have that problem. Maybe the oil strainer in the cases is plugged up. This is just a shot in the dark but maybe the gasket between the two cases is leaking and causing it to suck air and build pressure (however if it could suck air to build pressure it could also vent that pressure back out). Heck I don't know, never heard of such a thing.


One last guess maybe the little 3 ring o ring (#10) was left out, causing excess oil to be pumped into the crank case?

[bherriman]

:confused:

[fauxamish]

Ok, my turn to guess... Does it only pump oil out when its been WOT for a while? Such as in a TT race. If so, then I say the engine's been converted to kickstart and the dowel for the starting gear was removed, leaving a large gap between the left crankcase cover and the only hole going into the breather chamber. Don't laugh cause mine was doing this and I think I fixed it by putting the dowel back in.

[wckedclownz69]

wrong oil filter?? or in backwards?

[killer454]

oil cooler pluged slightly and the pump is having a hard time pumping the oil back up the feed line to the cooler their for tripping the pressure releif on the pump partway causing oil to loadup in the case.once this starts you will see a low oil situation in the resovour but when you fill the tank now you are way overfull because a lot of the oil that was suppose to be in the tank is actually backing up in the case.causing the oil to go out the crankcase vent hose when piston does each stroke.

lol,lol,lol,lol,lol

this is my luck and if this could happen it would happen to me lol

[jensenracing77]

i will tell you when i get home from work today.

[jensenracing77]

this may be a little long.
the first time i seen it was with an engine i built. the guy brought me a moose gasket set along with everything he wanted me to build his engine with. the center case gasket was not cut very good. i had to trim some of the bolt holes where it did not get cut good. well i cut it a little to much around the oil port that goes from the clutch cover to the stator cover. this oil port is right above the crank case breather baffle that is built into the case. the oil port was leaking into the breather baffle. the normal crank case pressure would blow LARGE amounts of oil into the intake where the breather attaches.
before i figured it out i called a well known engine builder and he had no idea of the problem. a year later he called me to ask what i found because he had the same thing happen. (he made me promise not to tell anyone so i won't mention his company) his ended up being that the center case gasket just was not in the correct position when he tightened it up.
much later i had an old race buddy call me. he had a NEW 400EX that was doing the same thing. he knew that i had experienced most everything you can emagin on a 400 engine. i told him what the problem was. he took it to the dealer and they fixed it under warranty.
just a little triva that may help someone out if you ever see it happen.

[jensenracing77]

i tried to circled the oil port but it did not show up in the post.

[fauxamish]

Thanks, I think this might be whats wrong with mine, although I haven't noticed it blowing oil lately.

[jensenracing77]

if this is the problem it won't go away. also it will pump alot of oil into the air box and also smoke like you can't imagine if you keep going. it will suck the oil up the intake to the carburetor. but it will also run like a new one till it get to much oil into the intake. it is also starving the clutch and main shaft for oil when this happens.

[fauxamish]

Mine would be good for about 5 laps, then it would start pumping the oil into the intake. I pulled the breather tube and made one out of vinyl hose and put a bottle at the end to catch most of it. Mine only does it when I've been running it REALLY hard. During some practice laps, it didn't do it, but it did during the race. I'm putting a stroker in soon, so I'll make sure my crankcase gasket is lined up properly.