Air blowing out breather


10 replies to this topic
  • Ratcity

Posted August 30, 2011 - 06:52 AM

#1

I've got an 08' YZ 450 with an 09' motor and the breather tube that comes out of the top of the motor is blowing LOTS of air. There isn't any oil coming out of the tube and the bike is running ok right now. Somebody said that the piston rings need to be replaced but that doesn't sound right to me. I would think that the valves would need to be adjusted or replaced or something. Has anybody else ever seen this?

  • grayracer513

Posted August 30, 2011 - 10:50 AM

#2

If the piston in your engine moves 450cc of air in and out of the engine with its top, how much air do you suppose the bottom of it moves, and where would you think that goes?

  • sneek24

Posted August 30, 2011 - 12:59 PM

#3

If the piston in your engine moves 450cc of air in and out of the engine with its top, how much air do you suppose the bottom of it moves, and where would you think that goes?


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  • grayracer513

Posted August 30, 2011 - 02:00 PM

#4

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Very well, then, what is the answer, young sneek?

  • blakers213

Posted August 30, 2011 - 04:12 PM

#5

My almost new 09 blows so much air out the breather hose I was thinking about adding a slip on exhaust on it. Completely normal. No need for new rings.

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  • Theeebalz

Posted August 30, 2011 - 04:21 PM

#6

correct me if i'm wrong but, isn't the only way to really determine need for new rings blow by from the oil fill plug?

  • grayracer513

Posted August 30, 2011 - 09:10 PM

#7

correct me if i'm wrong but, isn't the only way to really determine need for new rings blow by from the oil fill plug?

Very well, you're corrected.

The crankcase breather is as open to the crankcase as the oil fill plug is by design.

At an idle, there is time enough between the up and down stroke of the piston that a considerable amount of air is moved back and forth within the breather hose. If you put a finger over the end, you'll feel the pulse between pressure and vacuum. As the engine speeds up, the time between pressure reversions decreases, and the air just compresses and decompresses under the piston without having time to move in or out of the hose.

The only way to definitively check for the need for ring replacement is a cylinder leak down test.

  • Theeebalz

Posted August 31, 2011 - 12:13 PM

#8

no no no. not the breather tube, like the oilfill. like i know a little is okay but like ALOT like it hits you in the face from a few feet away type thing?

  • grayracer513

Posted August 31, 2011 - 12:15 PM

#9

Assuming the engine is in perfect health, I do not advise opening the oil fill on a running 450 single unless you want to clean up the mess all by yourself.

  • wags450

Posted August 31, 2011 - 01:38 PM

#10

Assuming the engine is in perfect health, I do not advise opening the oil fill on a running 450 single unless you want to clean up the mess all by yourself.


:):lol::):lol: My first time checking the oil i did that......DONT DO IT

  • sneek24

Posted August 31, 2011 - 01:44 PM

#11

My almost new 09 blows so much air out the breather hose I was thinking about adding a slip on exhaust on it..


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