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Crank case venting options

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Ok guys, I am back with another topic that has me confused and I sure could use some guidance.

 

I understand this topic has been discussed hundreds, if not thousands, if times before. The one thing that no one has really focused on was the restriction/derestriction of moving air from the crank case vent. I started looking into this while I was checking my valves. I noticed there were some debris/particulates in the vent hose that went up to the crankcase. Having noticed oil in the airbox before I had an "Ah-ha!" moment and realized that since this was the vent for the crankcase fumes, that under the right conditions, the hose could reverse direction and suck in anything near it. I have read that this could only happen during a few unique situations and I most likely will not encounter them. 

 

I have my airbox cut open so it sees a fair share of dirt and dust. So, I am thinking about this to see if there is an economical solution. I thought about putting a filter on the end of the breather tube but then the oil would have no place to go. I have also seen some people add a T connector (usually on the YZ's) to drain the oil to the ground, but this option doesnt appeal to me since I am trying to ensure the purity of the air that 'might' get sucked back into the valve cover. 

 

I have used an oil catch in the past on most of my vehicles with great results. Since we arent venting huge amount of oil I thought a non baffled can (just a place to catch the oil so it didnt block the vent line) would work with the exit line going to a high point with a filter. I found little oil catch cans for go karts in the range of $20. Problem is they are only sized for 1/8" NPT. I assume since Yamaha had some reason why they made the vent hose 1/2". How would this reduction in vent hose diameter negatively affect the engine? Has there been any other solutions that people have used to both displace the oil vented properly and ensure clean air return should the direction of flow ever reverse? 

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Everytime you stall or start your motor you pull air into the crankcase vent....but not enough to displace the air that is already in there.

Use a crankcase vent filter if you are worried, but it is a non issue. 

The dirt you see is coming more likely from your carb vent hoses, which suck in TONS of dirt. Re route them up above the tank, and filter them too. 

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1 hour ago, THE KRAN said:

Everytime you stall or start your motor you pull air into the crankcase vent....but not enough to displace the air that is already in there.

Use a crankcase vent filter if you are worried, but it is a non issue. 

The dirt you see is coming more likely from your carb vent hoses, which suck in TONS of dirt. Re route them up above the tank, and filter them too. 

All 4 of them (other than the overflow) are vent tubes that can suck up dirt? Would any fuel be vented out of those 4? Would a carb catch be a simpler option? 

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8 hours ago, Nixinus said:

All 4 of them (other than the overflow) are vent tubes that can suck up dirt? Would any fuel be vented out of those 4? Would a carb catch be a simpler option? 

All four vent lines suck when the motor stalls or starts. A catch can is for dirt free environments like street/sumo

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4 hours ago, THE KRAN said:

All four vent lines suck when the motor stalls or starts. A catch can is for dirt free environments like street/sumo

So why would they be placed closest to the ground and dirt? I assume it is because they also vent out fuel. What conditions amd why would the carb to need to vent fuel out?

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3 hours ago, Nixinus said:

So why would they be placed closest to the ground and dirt? I assume it is because they also vent out fuel. What conditions amd why would the carb to need to vent fuel out?

Carbs need atmostpheric pressure to work. All manf have always done it that way, cause it's cheap. Only the overflow tube leaks gas....unless you go upside down, then they all do.

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