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BrianM450F

ALOT of oil from breather tube

11 posts in this topic

Ive did a search and found some related threrads but none that seem to fit my prob. Ive got A 06 450F that seems to be running fine except that has ALOT of oil coming from the valve cover breather tube. I did the re-route mod with the tube running into the air box and I thought that might help but it didnt. It is literally pumping the engine dry!!! My question is what are any or all of the things that could cause ALOT of oil to be doing this? cracked head, blown head gasket, oil pump, stopped up oil passage, ect... ???? Any help would be awesome. thanks

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I suppose you checked that oil is not overfilled... maybe a clogged breather ? It could be worn rings that cause compression to pass thru the crank, but I'm not sure. Another possibilitie is a clogged oil passage in your bottom end causing too much oil pressure to go to the head.

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The compression is good and its not over filled, in 20 mins of riding yesterday it pumped enough oil out that it barely touches the dip stick now. Im not sure what you mean by a clogged breather? explain a lil more. .

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Neither a blocked oil passage or a clogged breather will cause this. If the pressure balance vent running from the tank section to the crankcase cover is not open into both volumes, it can cause trouble, but probably not what you are complaining of.

When did this start?

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Neither a blocked oil passage or a clogged breather will cause this. If the pressure balance vent running from the tank section to the crankcase cover is not open into both volumes, it can cause trouble, but probably not what you are complaining of.

When did this start?

Gray I will answer this for Brian. This is a bike I sold to him. It was my sons and before I sold it I pretty much did a complete top end rebuild. Cylinder, piston and valves. When I put it back together I over touqed one of the head bolts and worped the head. A machine shop fixed it and it now seems fine as in it does not loose coolant and seems to run fine. But, it is blowing oil out the breather hose. Could the rings have not seated? Could the head still be worped? What else could be causing pressure to build up? Brian said he drained the oil from both sides and filled with 1.3qts. Could it still just have to much oil? It seems to have plenty of compresion and is not smoking or using coolant. Could any return oil passages be clogged leaving the oil with nowhere else to go?

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Brian said he drained the oil from both sides and filled with 1.3qts. Could it still just have to much oil? It seems to have plenty of compresion and is not smoking or using coolant. Could any return oil passages be clogged leaving the oil with nowhere else to go?
1.3 quarts is too much oil, yes, and it will cause oil blowout since the excess can't be scavenged from the crankcases. If you drain both volumes (the dipstick MUST be removed while draining the "tank") AND change the oil filter , the bike takes precisely 1 liter (1.07 qt). This is simpler tio measure out than many people make it, in most cases. Most oil bottles have a one liter mark on them, even though there's only a quart in the bottle. Take a full bottle and fill it to the one liter mark from another one, then dump it in without another thought.

The return passage could not be blocked off without starving the engine eventually, and the oil level in the tank would drop to critical in much less than 20 minutes. It could be partially obstructed though. Almost the entire return circuit is accessible from outside. First try adjusting the oil level and see what that does. Also be sure the vent I mentioned earlier is open to both the crankcase and the tank section. If you still want to check the return circuit, remove the ignition side crankcase cover. Turning the engine over should, if there is oil in the engine, immediately push oil out of the return passage from the pump. Air blown in through the passage to the tank should come out the dipstick hole without restriction. You can also check the passage in the case cover.

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Hopefully it is simply an effect of having almost 30% too much oil in the bike.

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I have the same problem on my sons bike (2007 YZ450) however he may have over filled his oil.

Do you check these 4-stk's oil with the motor warm or cold... sorry for the newb question

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On any bike it's more accurate when warm. On a dry sump system like the YZF, oil level can only be checked after the engine has been run for a minute or so. Remove, clean, and reinsert the stick without threading it in.

A problem unique to the '06+ YZ450 is that overfills won't show on the stick because the no extra space in the tank for the excess. It just gets forced back to the crankcases and causes trouble.

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The problem with the bike blowing oil out the vent tube was blow-by. Did a leak down test and it blew right by the rings like they werent even there. One of the ring lands had a ring stuck. NO cross hatch marks in cyclinder. Dont really know how the bike even ran. Besides the head being fubar when I got the bike. Now with the bike torn down, cylinder off and piston out, I have found that the wrist pin and cam juornals have some galding... i wonder what the bottom end looks like :ride: and i havent even got a chance to ride it enough to know if the head is good :p

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So both the statements here were false.

The compression is good and its not over filled,
See why this is hard to do?

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