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Valve cover breather hose

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On a 2010 crf 250r fuel injected bike where does the breather hose go that comes from the valve cover

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just guessing here, (well im pretty sure by memory)

but should go into a t-piece one hose goes to the airbox and another down to the bottom of your shock and should have a drain plug on it

Edited by nks0

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just guessing here, (well im pretty sure by memory)

but should go into a t-piece one hose goes to the airbox and another down to the bottom of your shock and should have a drain plug on it

oh well my buddy just bought a 2010 crf 250r and it's missing the hose and he said it blows oil out

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id make sure he hasn't overfilled the engine oil

if no problem there

id change piston n rings 

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That is a crank case breather. It runs down into the case above the transmission and runs into the air box and it runs into that clear tube right above the front sprocket guard. Make sure you drain what ever is in there after every wash, or muddy trail day.

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It runs down into the case above the transmission...

The crankcase breather does not go into the case above the transmission. The transmission has its own separate breather hose, which comes off the top of the case and is routed out the bottom of the frame next to the rear shock. The crankcase breather hose coming off the valve cover leads to a Tee fitting, with a suction hose leading to the airbox and a pink translucent drain hose that secures to the left side of the swing arm.

Edited by mossman77

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Whats the reasoning behind the tube going to the airbox? Ive read on here and several other places you can disconnect it and just run one tube down with no plug.

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Because the airbox provides suction and it is filtered. The block off kits you see omit the drain and put a filter on the end of the vent tube to prevent dirt, dust, etc from getting sucked into the head. I recently installed a vent kit on my 250X and chose to retain the drain hose. This required using my own tee fitting because the hoses are different sizes. I have 49 tee fittings leftover if you want one (minimum order was box of 50). Otherwise, you vent and drain through the provided filter. I didn't like that idea which is why I chose to mostly retain the stock setup, only with an external filter in place of the airbox.

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I couldnt edit the post but I should have said I disconnected the air box from the line years ago in there. I do have a filter on the end of the line, but its just out of the valve cover and straight down. I always wondered about the suction because arent you always going to have pressure from the crank case? If I take the filter off you can see air blow out of the tube.

Edited by CRFRida1605

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I don't know for certain, but the filter is there for a reason. Maybe there are certain conditions when the case is under negative pressure. Or when your bike isn't running, you wouldn't want an open tube leading into the heart of your bike. The tranny vent doesn't have a filter on it though, so there goes that logic.

Edited by mossman77

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The hose coming out of the cylinder head cover? That's this crankcase breather hose.

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ah i see my errors - its setup different than the bike i have now (450x) i don't have my 09crf250r anymore

yeah the other one is the tranny breather.

i wouldn't call the valve cover breather a crankcase breather but thats just me.

Edited by nks0

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All valve cover breathers are crankcase breathers.

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The crankcase vents through the valve cover where the timing chain passes, hence the name crankcase vent. The valve cover doesn't need venting.

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