Milkly Blowby after jettting? 2008 Yz450f


4 replies to this topic
  • 08YZ450F

Posted April 04, 2008 - 03:12 PM

#1

I have a Full Factory 4.1ti exhaust (powerbomb header), twin air air filter, and just bought a Dyno Jet Stage 1.

I put in the jet kit with the provided instructions, Took it out for a quick ride to see how it ran. Bike runs fine just a lil pop on decel. I put the bike in my garage and went to eat. Came back an noticed a milky colored substance coming from the valve cover breather tube. I know its not good to have that color coming out of an engine.

Heres the Jet Specs.

Main Jet - 160
Fuel Needle - 3rd groove.
fuel screw 2 1/2 turns out

the kit comes with a 165 main jet. 160 sounds a lil lean but it was the suggested jet for my mods/elevation

Seems like water in the oil. I just bought the bike less than a month ago so I dont think the water pump seal/propeller would be the cause.

  • todds924

Posted April 04, 2008 - 03:18 PM

#2

I have a Full Factory 4.1ti exhaust (powerbomb header), twin air air filter, and just bought a Dyno Jet Stage 1.

I put in the jet kit with the provided instructions, Took it out for a quick ride to see how it ran. Bike runs fine just a lil pop on decel from time to time. I put the bike in my garage and went to eat. Came back an noticed a milky colored substance coming from the valve cover breather tube. I know its not good to have that color coming out of an engine.

Heres the Jet Specs.

Main Jet - 160
Fuel Needle - 3rd groove.
fuel screw 2 1/2 turns out

the kit comes with a 165 main jet. 160 sounds a lil lean but its was the suggested just for my mods/elevation

Seems like water in the oil. I just bought the bike less than a month ago so I dont think the water pump seal/propeller would be the cause.


You have a leaky water pump seal.

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  • Yamkifour

Posted April 04, 2008 - 04:32 PM

#3

You have a leaky water pump seal.


Its not the water pump. Water is a product of combustion and it has also been very wet here in PA. You did a quick fire up and shut down. The moisture in the engine crank case was starting to come out. This is common on four stroke engines. Just like cars when the engines warm up they will purge the fuel and moisture from the crankcase after reaching normal operating temp. This is why they tell you to change your oil every 3 months or 3000 miles(in cars). People who do real short trips never fully purge there crankcase which is harder on their oil. I always see cars with the oil cap up high on the motor, have the same milky substance collect on the inside of the cap. I am shure GR will have a more tech explain. This is my simple explain

  • zao

Posted April 04, 2008 - 05:06 PM

#4

Mine does this do. i do not worry about it since when i change the oil it is not milky. The dip stick does not have the milky looking oil on it and neither does the oil filter. I think it is just excess mositure in the breather hose.

  • grayracer513

Posted April 04, 2008 - 07:35 PM

#5

In the absence of any evidence that the oil itself is contaminated, it's condensation, and nothing to worry about.

Under normal circumstances, water pump seals cannot contaminate engine oil on a YZF. When these leak, they leak into a gap between the coolant seal and the impeller shaft oil seal, and this gap is vented to the outside via the weep hole under the water pump. There are seals at the right engine cover, the base gasket, and the head gasket that can contaminate oil, though.





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