Losing oil from crankcase breather hose. ? 06 crf 250r

huck2flat
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huck2flat
Edited Date/Time 7/20/2015 4:18pm
So I have a 2006 Honda CRF 250R, and it's leaking a significant amount of oil out of the crankcase breather hose. I'll change my oil to factory spec, then making sure it's all the way to the top line on the dipstick. But after about 30 minutes on the meter, if that, it's near or below the bottom line on the dipstick and my linkage is covered with oil.
Also, the entire motor is new with just over 10 hours. It has a new crank, piston, cam, cam chain, valves, seals, gaskets etc.. Everything is new..
I did notice that the crankcase breather hose doesn't appear to be stock as it's larger diameter and there's no plug in the end of this hose like with the stock one. Another thing, that hose that's supposed to go from the airbox and connect to the crankcase breather hose is non existent. It looks to have an aftermarket red anodized plug plugging the hole in the air box. I believe this setup is made by Tokyo mods to eliminate the dirty air from going back into the motor or something like that..
Not really sure what to do. I've just been making sure to add oil every moto or practice session so I don't hurt anything inside by running it empty. Just curious what the problem could be.
I also created an account and made a forum on TT but didn't gather a ton of information. Hoping I'll have better results here.
Any help would be appreciated.
Thanks
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NHtoWA421
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NHtoWA421 7/6/2015 8:58pm
7/6/2015 8:58pm
My 06 yz450 does the same thing. Started pretty much after the motor was done. The whole 9 yards. Honestly, i have no idea either, but suspect a cracked ring and will probably start there.
hillbilly
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hillbilly 7/6/2015 9:02pm
7/6/2015 9:02pm
there is a seal on the crank that seperates the tranny oil from the crank oil.

you need to drain both and measure out the oil that drains then refill with the correct CCs of oil.

ride it the check amount and see if it is transfering by that seal.
mmitoptech
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mmitoptech 7/6/2015 9:22pm
7/6/2015 9:22pm
This^^^^^
Berm
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Berm 7/6/2015 9:46pm
7/6/2015 9:46pm
^^^^^ happens alot on crf and trx motors, although usually caused by a missing bolt for the trx.
hillbilly makes the most sense considering it was recently rebuilt. Either they used the same old crank seal, cracked the seal putting it in, or forgot a bolt through which the oil transfers (not sure if that is possible on crf motors though).

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Redrcr34
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Redrcr34 7/6/2015 9:47pm
7/6/2015 9:47pm
Mine did the same thing on a 07 crf250, crank seal was bad.
huck2flat
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huck2flat 7/6/2015 9:53pm
7/6/2015 9:53pm
hillbilly wrote:
there is a seal on the crank that seperates the tranny oil from the crank oil. you need to drain both and measure out the oil...
there is a seal on the crank that seperates the tranny oil from the crank oil.

you need to drain both and measure out the oil that drains then refill with the correct CCs of oil.

ride it the check amount and see if it is transfering by that seal.
So if the tranny oil was transferring to the motor oil side, then it would be spitting out excess oil from the crankcase breather hose, right? But wouldn't that mean my motor oil would constantly be overfull and showing so on the dipstick? That's what makes me think it wouldn't be that seal.
huck2flat
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huck2flat 7/7/2015 8:09pm
7/7/2015 8:09pm
..
hillbilly
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hillbilly 7/7/2015 10:23pm
7/7/2015 10:23pm
hillbilly wrote:
there is a seal on the crank that seperates the tranny oil from the crank oil. you need to drain both and measure out the oil...
there is a seal on the crank that seperates the tranny oil from the crank oil.

you need to drain both and measure out the oil that drains then refill with the correct CCs of oil.

ride it the check amount and see if it is transfering by that seal.
huck2flat wrote:
So if the tranny oil was transferring to the motor oil side, then it would be spitting out excess oil from the crankcase breather hose, right...
So if the tranny oil was transferring to the motor oil side, then it would be spitting out excess oil from the crankcase breather hose, right? But wouldn't that mean my motor oil would constantly be overfull and showing so on the dipstick? That's what makes me think it wouldn't be that seal.
that is why you need to know exactly how much oil is inneach side CC wise.

then ride it a while and drain both and measure.

check the hose on the valve cover to be clear also.

hillbilly
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hillbilly 7/7/2015 10:38pm
7/7/2015 10:38pm
you may be over filling it. The dipstick is unreliable,you know the oil is in there but no idea how much.

once you put thr correct amount in then you could note where it is on the stick.
huck2flat
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huck2flat 7/8/2015 1:31am
7/8/2015 1:31am
hillbilly wrote:
you may be over filling it. The dipstick is unreliable,you know the oil is in there but no idea how much. once you put thr correct...
you may be over filling it. The dipstick is unreliable,you know the oil is in there but no idea how much.

once you put thr correct amount in then you could note where it is on the stick.
Possibly, but I always put in exactly what the manual calls for. But I'll make sure to measure both sides and see.
Thanks for the help so far everyone. Hopefully I can get this problem situated soon..
rallendude
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rallendude 7/8/2015 6:51am
7/8/2015 6:51am
You mentioned two different hoses and the stories don't add up. There should be a crank case breather hose off the top of the case just below the carb and a little to the right.

There should also be a breather hose coming off the back of the valve cover. That hose should go back around the carb to a plastic Y. The other two legs of the Y should have hoses going to the airbox and then down around the countershaft area. That is the hose that should be plugged. The crank breather hose should never be plugged.

If the airbox hole is plugged then make sure you have a single vent hose coming off the valve cover and it must be open. Otherwise, you'll pressurize the valve cover and that pressure must go somewhere. Usually out through the crank seal, with your engine oil.
hillbilly
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hillbilly 7/8/2015 8:00am
7/8/2015 8:00am
hillbilly wrote:
you may be over filling it. The dipstick is unreliable,you know the oil is in there but no idea how much. once you put thr correct...
you may be over filling it. The dipstick is unreliable,you know the oil is in there but no idea how much.

once you put thr correct amount in then you could note where it is on the stick.
huck2flat wrote:
Possibly, but I always put in exactly what the manual calls for. But I'll make sure to measure both sides and see. Thanks for the help...
Possibly, but I always put in exactly what the manual calls for. But I'll make sure to measure both sides and see.
Thanks for the help so far everyone. Hopefully I can get this problem situated soon..
make sure the hose on the rocker cover is clear ,
mxtech1
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mxtech1 7/8/2015 8:17am
7/8/2015 8:17am
Hillbilly gave you the best way to figure out what's going on.
Kawisrok
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Kawisrok 7/8/2015 1:04pm
7/8/2015 1:04pm
My KX250F will do the exact same thing if I fill the oil up to the full line. I hasn't done it since I started measuring the oil I put in according to the required value listed next to the fill cap.
huck2flat
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huck2flat 7/8/2015 10:08pm
7/8/2015 10:08pm
rallendude wrote:
You mentioned two different hoses and the stories don't add up. There should be a crank case breather hose off the top of the case just...
You mentioned two different hoses and the stories don't add up. There should be a crank case breather hose off the top of the case just below the carb and a little to the right.

There should also be a breather hose coming off the back of the valve cover. That hose should go back around the carb to a plastic Y. The other two legs of the Y should have hoses going to the airbox and then down around the countershaft area. That is the hose that should be plugged. The crank breather hose should never be plugged.

If the airbox hole is plugged then make sure you have a single vent hose coming off the valve cover and it must be open. Otherwise, you'll pressurize the valve cover and that pressure must go somewhere. Usually out through the crank seal, with your engine oil.
Yes, I'm aware there's two different hoses, but I'm talking about the one coming off the valve cover. I've always know it as a crankcase breather hose, and it has a single aftermarket hose that bypasses the airbox to eliminate the dirty, hot air from going back into the motor so that's why it came with the little plug so it wouldn't just be open and suck unclean air. Also neither of them are plugged. Sorry if I wasn't clear enough haha
huck2flat
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huck2flat 7/18/2015 11:37am
7/18/2015 11:37am
So when I drained and measured the tranny oil after a day of riding it was still to spec. So I have my doubts it's the seal that separates the two sides. Another person said it could be a cracked ring, but it would be burning oil and smoking if that was the case, wouldn't it?
Paw Paw 271
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Paw Paw 271 7/18/2015 12:57pm
7/18/2015 12:57pm Edited Date/Time 7/18/2015 12:58pm
If the plug is not in the breather hose, you can actually pull dirt the engine and cause some real wear issues. The factory hose routing allows the blow by to reinter the air box while catching and condensated oil in the tube with the plug on it. This also keeps dirt from entering the engine.


Paw Paw
huck2flat
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huck2flat 7/20/2015 2:17pm
7/20/2015 2:17pm Edited Date/Time 7/20/2015 2:19pm
Paw Paw 271 wrote:
If the plug is not in the breather hose, you can actually pull dirt the engine and cause some real wear issues. The factory hose routing...
If the plug is not in the breather hose, you can actually pull dirt the engine and cause some real wear issues. The factory hose routing allows the blow by to reinter the air box while catching and condensated oil in the tube with the plug on it. This also keeps dirt from entering the engine.


Paw Paw
It would seem very difficult to suck dirt into the motor since it's blowing out so much smoke and oil from that hose. But I guess it's possible.. Also, in the description of the aftermarket hose routing by Tokyo mods it says it actually increases reliability and power.

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Paw Paw 271
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Paw Paw 271 7/20/2015 4:03pm
7/20/2015 4:03pm
If you want to test this...Crank the bike...Now hold a piece of paper over the open hose end and rev the engine...
You will see the paper blow away from the hose as the bike revs, but the paper will be drawn to the paper when the throttle is closed and the rpms decrease.

Paw Paw
huck2flat
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huck2flat 7/20/2015 4:18pm
7/20/2015 4:18pm
Paw Paw 271 wrote:
If you want to test this...Crank the bike...Now hold a piece of paper over the open hose end and rev the engine... You will see the...
If you want to test this...Crank the bike...Now hold a piece of paper over the open hose end and rev the engine...
You will see the paper blow away from the hose as the bike revs, but the paper will be drawn to the paper when the throttle is closed and the rpms decrease.

Paw Paw
Oh, I see.

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