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How much pressure does it take to open the oil check valves or a way to tell if they

Y

yz400ex

Well-known member
Feb 8, 2009
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Idaho
Rebuilt this sleds top end just over a year ago, but the sled was only started after the rebuild and ran for a few minutes. The sled had been sitting for over a year and when I opened the hood, there was oil dripping out from between where the Y pipe meets the pipe. Pulled the pipe and the PTO side of the y pipe had lots of unburned oil in it. Pulled that off and oil slowly started coming out of the exhaust port. Pulled the cylinders and found the entire PTO side of the crankcase is filled with oil. Figured it slowly came through one of the check valves and over a years time it filled the case.

There is a check valve on the PTO side of the engine and 1 in the PTO side carb. I am able to push oil though both of these and a new spare check valve using a syringe. To me, it feels like the amount of pressure needed to open the valve for oil to come through is the same for all of them. Is there a full proof way to determine if a check valve is faulty or weak? Is there a certain amount of vacuum or pressure needed to make them open?

Sorry for the long post, but figured I should explain everything before asking the question. Can anyone help me with this? Thank you for your time..

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sled_guy

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Premium Member
Jul 5, 2001
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Riverton, Utah
Well, you don't have to worry about that crank bearing being rusty do you?

I don't know how to tell you to measure the resistance, but I would think if you can't blow through them then that would be enough resistance to keep them from leaking.

I wonder, could you be leaking past the oil pump in the crank case some how?

sled_guy
 
Y

yz400ex

Well-known member
Feb 8, 2009
1,866
212
63
Idaho
Well, you don't have to worry about that crank bearing being rusty do you?

I don't know how to tell you to measure the resistance, but I would think if you can't blow through them then that would be enough resistance to keep them from leaking.

I wonder, could you be leaking past the oil pump in the crank case some how?

sled_guy

I don't think it is leaking past the pump because it's just the one side of the case that was full of oil. That's why I figured it was either the check valve in the carb or the one behind the primary clutch.

I didn't try and blow any air through any of the valves, so I'm not sure if I could do that or not. I just used a large syringe and pushed 2 stroke oil through them and tried to compare how easy it was between the 2 valves in question and the new valve I had. I honestly couldn't tell the difference between the 3 of them though.

Check your check valves with a Needle Blow Off tool.. For Carbs..

I am not familiar with this tool. Anymore info?
 

NapaMatt

Matryx 850 Pow Slayer!
Lifetime Membership
Mar 13, 2009
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Stewartville, MN
www.napaonline.com
Tool is called Pop - Off Gauge..

$48.95 for the tool from part unlimited

## MK-BN-PNP

Made by Mikuni!

I can order one if you want one,,

Well heck I can beat amazon! Screw the big corp! Support the little guy! lol

$40.00 !!
 
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