Oil in Airbox

I just finished my 05 tope end and took the bike out for some trail riding. An hour into it, I noticed the swing arm COVERED in oil. The sight glass on the oil side didn't read at all even with the bike tipped. What in name of all that is holy would cause the breather sytem to empty all the oil in the engine? Valves are brand new. We ended up pushing the bike 6 miles to the truck so we didn't seize it up. Anybody have any ideas? I have heard of a seal or something that goes out between the cases. Is there any other possiblity of why it would spew that much oil that quick. Thanks for the help guys.

Oil seals. Not a big job to do. Not an uncommon CRF issue.

which seals do you need. i have a friend with the same issue. its an 03 crf450r and it might last 2 laps on the motocross track before its out of oil. part numbers or a diagram would be very benificial. thanks

To add to the previous post it is out of motor oil the tranny oil is fine. The motor had a new piston and rings and valves done about 3 months ago and has been running fine. This happened all at once and has restricted him from riding. for about 2 weeks. i have checked on posts about oil migration. but most of them talk about tranny goin to motor oil. the issue we are having is the engine oil coming out of the breather tube. we have checked the tubes for blockage nothing there the baffle is fine in the valve cover. the guy is ready to sell the bike on ebay and go back to 2 strokes. any info would be great. the oil that leaks out isnt a drip it is severe. it makes for a hell of a chain luber.

If motor blows oil out of cranckcase trough the breather tube the cranckcase must be over-pressurized. (piston blow-by)

Seems like a ring/piston issue: could be bad ring seating or more likely rings assembled wrong (are marks up and gaps divided 120 degrees ?)

i hate being that guy but, why do you always seem to get the guys that post stuff that doesnt help a bit. like the guy that says put your dipstick in and check the oil. first the crf450r doesnt have a dipstick and im not sure if it wasnt posted correctly in my last post but it is out of oil in 2 laps. which would mean it wouldnt matter how full it was with oil, its completly empty.the other comment it has been together and ran and raced for a couple months so i dont think that its the rings, at least not from improper installation.we are hoping that it isnt the rings.. that is our last resort to tear down that far. he has the athena big bore kit and the gasket set just to check and see if anything is wrong in the piston head area is $100+ for the gasket set. they dont sell just the head and or base gasket together at least not for the big bore kit. we got the oil seals on the flywheel side and are gonna install them tonight hoping that solves the problem. If the seals dont fix the problem i think the only other thing it could be would be a ring or valve problem. unless there are any other ideas that anybody could think of.

why replace flywheelside seal when not leaking?

Can't think of a way how leaking seals or valves pressurize cranckcase...

How is your compression? Runs ok? if not could it be a little crack in piston?

the bike runs fine, feels like alot of compression on the first kick, but after that you can't tell because the decompression valve kicks in. no i am not over filling it. i thought it might be the piston rings but right now i am will to try anthing that is cheaper that $250.00 right now i have $20.00 in the seals. i hate to tear this bike down right now since i am planning on tearing it down over the winter to put new crank and bearings in and new top end. i don't want to have to put alot into it right now just to be able to ride it for a month or so, maybe the guy that originally posted this topic may have put his rings in wrong or something to that effect. but mine has been running for 3-4 months then sat for two weeks i went to go ride next thing i know i have oil all over my swing arms, don't know if it was from me going down and the bike laying on its side and running may have damaged the rings or something else internal. thank you for your comments on this topic, hope the guy who posted about the oils seals no big deal posts back.

I would perform a leak down test on it. It sounds like a ring problem.

My 04 did the same thing years ago, was running fine then suddenly spewed all the oil out thru the airbox vent. It was the oil seals behind each side cover, I think on one side it is on the balancer shaft and I forget where on the other side. It is not your rings.

I narrowed it down to either rings or seals, but am stumped at which. If it was the rings, i would assume (can't see any reason why not) that the bike would be low on compression and blow smoke out the exhaust at least to some degree. Neither of those apply. Bike runs and pulls strong without any smoke. If it was the seals, I would suspect that the tranny side would have lost oil first and started making the screeching noises before the engine side emptied out. That didn't happen either. When I went to drain the oil in both sides, i got barely a dribble out of the engine side and probably half of a quart out of the tranny side. I would think that it should be the other way around if the seals were gone??? I refilled both sides with 20 oz of 10w 40 and I am going to go ride and see what happens. Any other ideas or much appreciated

Update: I can't figure out why not yesterday but definitely today. I refilled the tranny and oil side with manuel specs. I started the bike up and it was definitely burning oil. Now the big question is: Is the oil getting past the rings and burning in the cumbustion chamber, or is it getting sucked through the airbox that I didn't clean out from yesterday? Guess I will clean the box out and then start it and see what happens

Something similar happened to me and a friend of mine,we both had Athena big bore kits and at different times the piston would crack across the top of the dome.It would still run but would blow oil out the breather tube and coat the front side of the air filter and stop running.cheers

try doing a compression check. They make gauges you can use at any auto parts store. test the comp. then put some oil in the cylinder through the spark plug hole(just enough to coat the inside of the cylinder, it will seal any gaps in rings momentarily, then check it again. That will tell you if its the rings. Good luck if you don't understand that pm me.:confused:

Update, the oil burning problem seems to be from the airbox sucking in all the oil that spewed out the breather hose. As soon as I took the airbox off and ran the bike, the white smoke cleared up. But my problems are still aplenty. The bike will start within 4 kicks if i pump the throttle before I kick it, but even with the airbox off the bike it was still spewing oil out the breather hose from the vavle cover. I bought a leak down tester and hooked it up to the compressor with 70 lbs of pressure. Screwed the other end into spark plug hole and lined up the crank at TDC. When I hooked up the gauge, it registered NOTHING!!! All I could hear was the gurgling of oil somewhere down in the engine. There was no air coming from the intake or exhaust. The ONLY way I could get it to build any type of pressure was to put the valve cover back on and plug the breather hole with my finger. Then I could get it to go up to 12lbs. Anybody know what the name of hell is the deal. With the test as I did it reading 0 psi, the bike should not start at all. Correct??? I tryed the couple of tablespoons of oil down the hole and coated it good by cranking it over a few times, but the gauge still read 0 with air leaking like a bastard from somewhere. I wanna just right it off as bad rings, but with 0 psi, the bike shouldn't start or even come close to starting. Somebody help me with this biznatch before I lose my soul. :confused:


Time to tear it back down.

Hmm, that was a helpful response. Thanks Camp!!!

I hate to be the bearer of bad news. I'm usually the last guy to advise someone to tear it down when they have a problem.

check inside the air boot from the air box if there is dirt in there you wasted the rings and cyl. and piston, doesnt take much dirt to get by and it will do it, once the coating is rubbed off the cyl wall it will have blow by like you can not believe!

Thanks Moto. I just finished doing the topend, but refrained from doing the piston and rings because they seemed fine. In reality, I should have just bit the bullet and did the whole thing regardless of how things appeared. Next question is do I have to get a whole new jug? Is there a way of inspecting the cylinder wall to determine if it needs replacing. I figured it was fine because when I did the valves, I couldn't see any grooves and there was good crosshatching. As for the blow by, is it possible that the rings are so shot that the cylinder won't hold compression for a leak down at all? Thanks for the help guys

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