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YZ-F & YZ YZ250F, YZ450F, YZ250, YZ125, YZ80, etc.

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Old 02-27-2011, 02:27 PM   #1
MXrider224
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Default 2006 YZ450F problem

My yz450f has a problem that it spits oil out of the breather tube which comes from the top of the valve cover slowly. When the bike is shut off it drips for about 5 minutes. in about an hour of riding it the oil level drops from the mark on the dipstick to almost the bottom. The bike has good compression and runs great. it does not smoke at any trottle position. it does not bog. a lot of air comes out of the breather tube when the bike is running, i'm not sure if this is normal. Any ideas of what might be causing this problem.
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Old 02-27-2011, 05:44 PM   #2
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are you measuring the oil using the procedure in the owners/service manual?

if you are not doing the check oil level properly , by following the exact procedure then you could have too much oil in the bike

(this is why I use a precise measurement rather than sight glass or dip stick on dry sump systems)

if you do have too much oil in the bike It probably will end up frothing up and out the crankcase breather tube.


the service manual gives the exact amounts to be added on an oil change.
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Old 02-28-2011, 08:52 AM   #3
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could you take a picture of the puddle it creates? A bit of dripping out of the breather is quite normal.

Mac is right as well, make sure you are using the proper amount of oil, and not overfilling.


Unfortunately if you're really loosing a lot of oil out of the crank breather, that's usually a sign of excessive crankcase pressure. probably means the compression gasses are blowing by the rings and pressurizing the crankcase. do you know how many hours you have on the bike? might be top end time. But check the cheaper things first, like proper fluid levels.
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Old 02-28-2011, 04:18 PM   #4
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after draining the oil in the bike the manual says to add exactly one quart without an oil filter change. the bike had the right amount of oil. i can feel a mist of oil coming from the breather tube when the bike ir running and it drips a fair amount of oil for a couple minutes after it is shut off. i am not sure how many hours are on the bike i was told it was recently rebuilt. maybe he lied or maybe he put it together wrong. i am going to check the compression but i am pretty sure it needs a top end rebuild.
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Old 02-28-2011, 04:22 PM   #5
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that would also be my guess if the crankcase is getting over-pressured.

good idea with the compression check! let us know how it goes!
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Old 02-28-2011, 04:42 PM   #6
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Quote:
Originally Posted by 4literranger485 View Post
could you take a picture of the puddle it creates? A bit of dripping out of the breather is quite normal.

Mac is right as well, make sure you are using the proper amount of oil, and not overfilling.


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Originally Posted by MXrider224 View Post
after draining the oil in the bike the manual says to add exactly one quart without an oil filter change. the bike had the right amount of oil. i can feel a mist of oil coming from the breather tube when the bike ir running and it drips a fair amount of oil for a couple minutes after it is shut off. i am not sure how many hours are on the bike i was told it was recently rebuilt. maybe he lied or maybe he put it together wrong. i am going to check the compression but i am pretty sure it needs a top end rebuild.
I would give it a ride or two before you rebuild the top end
as 4lr said there is a certain amount of oil that will froth up and end up coming out of the breather under certain conditions.
(maybe more if the bike runs inverted at any length) possibly exacerbated if you let the bike run after a get off or just frequent crashing LOL

unless you are actually seeing a constant "mist" coming out I would not give up hope that it is not just the remnant of the Possible original overfill problem.
btw you said you can feel oil mist coming out while running , can you see it on your hand or a paper plate?
let me be clear My 07450 and my08 250 do and did the exact same thing all the time new and with some seasons on them.
this is normal to an extent.
you can expect if you put your hand under the tube while running some gasses and pulsating air flow will occur. depending on conditions, frequency of rides, type of oil , and duration of run time this may be completely normal.

a huge puddle under the bike is not normal, but there are reasons this could be caused by things other than what has been speculated.
in fact the puddle under the bike (while sitting) actually leads me to believe it is not a blow by situation.


my guesses for possibly having too much oil in the bike are :
not draining all the oil out , caused sometimes by not knowing there are several places you are supposed to drain the oil from and an actual procedure for draining the oil. which is also important in filling -
the owners manual require a certain protocol that must be followed when checking the amount of oil on the dipstick or the reading is completely inaccurate.

so what I do is measure and then follow the manuals procedure to make sure there is little room for human error.
you could see where adding a quart of oil to a bike when not getting all the old oil out could cause there to be too much in the cc.
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Old 03-04-2011, 04:20 PM   #7
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I checked the compression and got 113 psi.which is low. I spoke to the previous owner to see if the bike had any problems. he said no of course. he said the top end only had about 7 hours on it when he sold it to me. he showed me the receipt and i believe him. but he said he never changed the cylinder or even re-sleeved it. which i am guessing is the part that is worn because he is the original owner since he bought it new in april 2006.
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Old 03-04-2011, 07:49 PM   #8
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it's a nikasil coated cylinder iirc

normally a piston and rings if done right are good to go

your bike has an auto decompression , so you will get around a hundred psi on a normal compression check

if it had a manual decomp like my 01 did then you could not kick through without releasing it . in other words you couldnt kick the beast for a compression check any way.

you would have to do a leak down test. but I'm sure it is not needed .

its obvious to me that you are looking for the answer you want. you have not listened to any of my advice so far . I'm done.
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Old 03-04-2011, 07:59 PM   #9
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did you do the oil trick?

add teaspoon of oil through the spark plug hole, if the compression starts to build up better, it's probably the rings.

if it doesnt go higher, it's probably leaky valves. have you checked valve clearances?
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Old 03-04-2011, 08:34 PM   #10
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Quote:
Originally Posted by 4literranger485 View Post
did you do the oil trick?

add teaspoon of oil through the spark plug hole, if the compression starts to build up better, it's probably the rings.

if it doesnt go higher, it's probably leaky valves. have you checked valve clearances?
you understand the part where I explained the bike has automatic decompression and regular compression tests oil or not are worthless.

this oil leaking thing is common for those who don't have a service manual or refuse to read it . dry sump oil systems have a precise step by step process for oil changes.
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Old 03-05-2011, 09:20 AM   #11
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Quote:
Originally Posted by macattack View Post
you understand the part where I explained the bike has automatic decompression and regular compression tests oil or not are worthless.

this oil leaking thing is common for those who don't have a service manual or refuse to read it . dry sump oil systems have a precise step by step process for oil changes.
mac you are absolutely right, i wasn't even thinking about the auto-decomp

my apologies

Now i know that the auto-decomp only works in low RPM situations (around 500-700 if memory serves). what is the proper way to compression check these engines?
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Old 03-05-2011, 01:30 PM   #12
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Quote:
Originally Posted by 4literranger485 View Post
mac you are absolutely right, i wasn't even thinking about the auto-decomp

my apologies

Now i know that the auto-decomp only works in low RPM situations (around 500-700 if memory serves). what is the proper way to compression check these engines?
Yeah sorry for being snippy, I think you're giving good advice.
Makes sense what you've said . If it is a
Compression related problem do you think a
Leak down test would show where the problem is?
I think there are too many unknown factors.
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Old 03-05-2011, 06:58 PM   #13
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i've never even tried that on one of these machines.

My last bike was a 426, with a decomp lever so it was easier. It seems that if the bike starts/runs well it should have decent compression. I'd like to see a picture of how much oil actually comes out of the breather tube. like you said, we could be troubleshooting normal ops here
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Old 03-07-2011, 04:49 PM   #14
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i wanted to be sure of how much oil was in the bike just in case i was doing it wrong. i drained both the oil tank bolt and crankcase bolt and measured it which came out to .80 quarts. i added oil into the container untill it read 1 quart. the container was very clean.and i put it back into the bike. i was planning on taking a picture of the puddle problem after i take a short ride. unfortunately about 5 minutes into the ride the engine seized. i was only a minute from my house.it wont kick over even with motor cold. i am going to start tearing the motor down this saturday.
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Old 03-07-2011, 05:16 PM   #15
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In the manual it details how to verify oil pressure
It's a step in an oil change - it's part of the oil change iirc,
Also I think there is a screen that requires inspection during an
Oil change.
I'm guessing it's not a lack of oil but a lack of oil flow maybe what caused the original problem -maybe oil was always in the
Bottom of the motor never circulating all the way round to. The tank
Those bikes can stay lubed at as little as a third of a quart from what I've experienced
I wouldn't have recommended riding it if you verified
It was losing oil though . That said ive been there it sucks

Hope it works out
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Old 03-07-2011, 05:35 PM   #16
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thanks for all the help. the bike had oil pressure before i rode it. there is a small 8mm bolt on the back of the head. if you loosen it and run the bike oil should seep out of it and it did. it had to seize from lack of oil. its my fault for even running it on low oil. it had to lose oil very quickly because after it seized, i drained all of the oil back into the measuring container and it had .45 quarts. the oil was clean which is a good sign. this is my first race bike so i am still learning about all this maintinance. moved up from an 08 crf230f. which requires minimal maintinance. i do take very good care of my bikes i will upload a picture of the 450 tomorrow.
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Old 03-07-2011, 05:45 PM   #17
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Old 03-07-2011, 08:11 PM   #18
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I mistakenly assumed the guy who rebuilt the bike would have caught any cylinder damage or taken it into a shop for inspection.
and I assumed he was rebuilding the bike under normal maintenance.
If it was a damaged cylinder , I'm doubting the original owner could have missed it. that is one nice thing about those type of cylinders . the bad thing is the price for repair.



let me know what you find , I'd like to help with the cost of the repair & I have some connections to save you some $$$
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Old 03-09-2011, 11:59 AM   #19
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This is my brothers 2009 crf150rb
DSC03322.jpgDSC03318.jpg
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Old 03-09-2011, 12:03 PM   #20
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this is my cousins 1986 xr250r
we recently rebuilt the engine because the center case cracked by the countershaft sprocket caused by a loose chain. the chain popped off the rear sprocket and lt locked up the rear wheel.
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