oil blowing out of 400ex breather tube HELP!!

[FQX13]

my 400ex is blowing oil out of the oil vent on my engine. i had a 426 JE 13.5:1 piston in it and my engine ran fine until the bearings went because of the high compression piston. we took the engine apart and there was metal everywhere. we used a parts washer and got all the metal out and put new bearings in. the quad ran great. then the piston blew because the cylinder walls were so thin because it was Bord out to a 426 and that is the most you can bore a 400ex out to. the sleeve cracked and there was metal everywhere in the trans again. we took it apart and washed out all the metal out. i bought a 440 kit that came with a 12.5:1 piston for my quad off ebay and had the new sleeve put in. we put the engine back together and i went riding. after 5 mins there was oil blowing out of my transmission oil breather tube that comes out right underneath the carb. we could not figure out what was wrong. we noticed that there was some oil around the top of the cylinder so we thought that it was the compression from the piston was blowing out of the gasket and into the cam chain slot and it was building up the crankcase with pressure and causing it to blow out. so we took the head off and put a high compression gasket on. then i went riding and it happened again. oil was blowing out the tube. we think that there might be metal clogging the valve for the breather tube and it is building up pressure and blowing out. if anyone knows what the problem could be or anything please let me know. thanks alot i would really like to figure out the problem and fix it then have to pay someone to. thanks alot.

[Rrider4life8]

is it alot of oil or just whenever you ride hard? my yfz blows some oil out of my tube from the engine but its normal

[sixer3]

ya all my 400's blow a little bit out of the breather tube every once and awhile, with the stock little resevoir thing, i have a small pool of it in all of em...i thought it was normal, hoppefully it is :)...and hopefully you dont have a whole lot, possibly too much oil?

[FQX13]

yea i have 20w 50 sicoleen oil in it. and i filled it up so its in the middle of low and high. and its just blowing out. like there is oil everywhere on my swing arm and everything. and i don't know whats causing it,

[Ex'r Marlin]

Originally posted by sixer3
... possibly too much oil?

That's what I was thinking too. But you say that the oil level is in middle of the low and high setting on your dip stick, right?

It was normal for me to see some oil blow by once in a while, but I never noticed a "pool" in mine. I wish I could help.

[rooster300ex]

Its either to much oil, overheating, or not put together right. no offense but are you a really good engine builder. when you beef an engine up you gotta beef everthing up. i could be to much stress on your engine parts.

[bradrenea]

If you are sure you filled up the oil properly then I would guess it is being caused by blow-by(rings). It could be that the rings just haven't seated yet or the cylinder was not honed properly, and they never will seat. I guess it's also possible that you installed the rings incorrectly.

Or if you did not install oversized head studs it could have blown the head gasket already.

[FQX13]

the oil is filled up to the middle of high and low on the dip stick. i had a machinist resleave my cylinder with the 440 and hone it. if i installed the rings in wrong dont you think that my quad will be smoking alot. and what do you mean by installing over sized head bolts? alright thanks alot.

[FQX13]

ok then i beefed my top end up....what would i have to do to beef up the trans? thanks

[GPracer2500]

Are you following the oil check procedure in the owners manual? Are you letting the quad idle for 5 minutes prior to checking the oil? Overfilling the oil is the most common reason for blowing oil out of the crankcase breather.

[FQX13]

i did not but, i filled my oil up and drove it for 5 mins and it pored out and i would think that it needs more oil because it gets in the valve cover and everthing. for some reason it is building up crank case pressure ad blowing it out. my engine ran fine with the JE 426 13.5:1 piston then i put a Weisco 440 12.5:1 piston in and its having this problem.

[GPracer2500]

You shouldn't check the oil after riding it at speed--let it idle. It needs to idle to normalize the oil levels in the tank and crankcase.

Not sure if that's your issue, but it's good oil-check practice.

[1fst400]

the blow by theory because the rings havent seated theory seems logical to me. But ab-normal.


call up colby at c&d racing, site sponsor. that guy can answer moast any question I throw at him over the phone.

[bradrenea]

Originally posted by FQX13
and what do you mean by installing over sized head bolts? alright thanks alot.

It's a necessary mod if you are running a high compression piston or you will blow head gaskets repeatedly.

As everyone else already stated, check the oil per the manual's instructions. If you don't let it idle before checking it will read low, and you will overfill.

[rooster300ex]

Originally posted by FQX13
ok then i beefed my top end up....what would i have to do to beef up the trans? thanks

Not really nessecary to do that. For a 440 to run right or be reliable everything needs to beefed up. larger head studs stop the small stock headstuds from pulling out,or to keep head gaskets from blowing on 440's.

[FQX13]

Originally posted by bradrenea
It's a necessary mod if you are running a high compression piston or you will blow head gaskets repeatedly.

yeah but i had a 426 with a 13.5:1 piston and everything was fine. i thew in a 440 piston with 12.5:1 piston and this started happening. if your sayin im gona blow head gaskets then i would have with the 13.5:1 and it never did. and with the 440 it didnt blow a head gasket. just for some reason it is blowing out oil. for some reason it is building up crank case pressure. and just blowing out. ill give that place a call when i get home and see if he can help. thanks everyone keep throwing out ideas

[FQX13]

from all the research iv been doin i think that this problem has somthing to do with the rings. from what i read it said my rings are allowing too much blow by. that means that the compression is going through my rings into my trans. i drained the oil and notivced that the oil was black, i found out that its because gas was getting into the trans because of blow by. if anyone else has anymore ideas please let me know. thanks

[bradrenea]

Hmmm. Seems like someone mentioned that several days ago.:D

Did you smell the oil to see if it smells like gas?

Did you measure the ring end gap when you installed the piston? Are you positive that you installed the rings with the right side facing up? If either of those are wrong it will deffinately cause problems.

Also, you replied to my earlier post that you did not think it was the rings because it was not smoking. It's possible to have a blow by problem without having any smoking.

[FQX13]

sweet