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Engine Oil leaking out of my CRF 450 air Box!b

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Don't know whats screwed but all my crankcase oil is filling up my lower air filter then dripping out on to my lower swing arm...Started about 3 rides ago. Currently I would guess I lost about 1/4 of oil capacity. I must also add the oil was very clean and clear in colour, is possible for oil to be blown by cylinder wall and still remain quite clean?

I own a CRF 450 2003

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the Breather hose routes to the air box. You may have over filled the engine a bit and when you rode it, it belched the excess oil out the over flow into the air box. Drain the line. Its got a plug in a reddish clear line near the on the case above the counter shaft sprocket. :cry:

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Don't know whats screwed but all my crankcase oil is filling up my lower air filter then dripping out on to my lower swing arm...Started about 3 rides ago. Currently I would guess I lost about 1/4 of oil capacity. I must also add the oil was very clean and clear in colour, is possible for oil to be blown by cylinder wall and still remain quite clean?

I own a CRF 450 2003

click here: Oil in airbox

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went out drained breather line as noted, I still feel there is no way that draining that line could prevent all the oil I've seen from getting out...I'm pretty sure the tranny oil is not mixing into the engine side. I do alot of high revving sand riding since the beginning of the year and have never drained that line until now

Where else or what else can I check!

Thanks in advance

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Hi!, my bike has also leaked lot's of oil from the airbox. When it started, I checked the possible causes and found that the intake valves had zero clearance and nearly the half of the tranny oil had moved to engine side. So there was two things that may have caused the leak. Or maybe they together caused it.

My suggestion is that you could check the intake valves, if no oil is moving to engine side. If they have zero clearance they could let some cylinder pressure to enter into the cylinder cover and this could push the oil into the breather tube

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verified that no oil is leaking into crankcase from tranny, just came in from garage and drained tranny side just make sure, the correct volume came out approx. 590ml

With all that done the suggestion the previous post is to remove cylinder head cover and adjust my valves and this will fix my problem!

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I also had the same problem. I ended up putting in a new top end and checking valves and still had that problem. The little over flow hose off the crankcase is where its coming from. If you dont drain that hose regularly it fills up and then puts all the excess out the bottem of the air box. Now I make sure to check and drain it regularly and havent had the problem since.

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If the trans oil is not migrating over to the engine side, recheck you oil level at the window after a 5 to 10 min ride.

The oil airates which increases the volume some, the excess could be pumped out the breather.

I don't run my breather to the air box or cap the end, it runs straight down...I relocated the wire holder to just in front of the counter shaft sprocket.

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