Oil Migration

[Pyroted]

I'll start by saying I did a search and didn't find any answers. ?

Is it possible for oil from the engine to migrate to the transmission? I noticed some oil consumption on my last trip to the dez. I had to add oil to the engine and when I checked the oil in my transmision, oil came out of the full hole like I way over filled it. I didn't measure it but it was several ounces.

Any help

[skipn8r]

I recall reading about a similar issue on the CRF250 board. I did a quick search, but couldn't find anything. If I recall right, there is a particular seal (maybe around the crank?) that keeps the trans and engine oils separate and can fail. I recall someone stating that when it did fail, his engine seemed low on oil, and when he refilled, his transmission was overflowing. Maybe you can try a search over there.

[Chris_in_the_Mojave]

I remember the same thread - It's the seal for the counter balancer. Poster said if it failed that oil could move from engine to tranny.

( Hi TED! ? )

[flmx4]

there is a "reed valve" type passage that allows pressure passage between the two motor halves that can go bad. The bad news is you have to split the cases to relpace it. Keep an eye on the levels if you don't replace it as the oil can quickly migrate from one side to the other.

[Pyroted]

Hey Chris, I was going to start doing some dez racing again. Have to put that on the back burner until I get the motor fixed

[tinman__327]

The reed passage is only to keep the engine oil full around the intake for the oil pump. The reed passage has nothing to do with the tranny side.

If there is oil migrating to the engine side it is the crank seal. Below the crank the reed valve only allows oil to flow out to the oil pump, but not letting it flow back under the crank. If the crank seal fails there is negative pressure that pulls oil from the tranny side into the engine side. Look at the fish and it is a little clearer.

If there is oil migrating to the tranny side it is the counter balancer seal, or a crack in the cases on an adjoining wall between engine and tranny. The needle bearing on the counterbalancer apparently go bad causing the seal to fail, could be from too low tranny oil level over time. I run 800 cc oil measured in the tranny and never had this prob.

The tranny oil migrating to engine side is pretty common, and pretty easy to fix.

[Pyroted]

Thanks Tinman, I had to add oil to the engine while out in the dez this last week. After checking the oil in the engine several times I decided to check the tranny. Oil kept coming out of the full indicator hole. Way more than if I over filled it. Anyway sounds like the counter balance seal. I have a shop manual on order and will be checking into what it will take to get this thing going in Prime riding season. ?

[Chris_in_the_Mojave]

Hey Chris, I was going to start doing some dez racing again. Have to put that on the back burner until I get the motor fixed

I'm on the sidelines right now as well... A/C sep and cracked ribs ?

Should be back on the bike in January. ?

Let us know what you find when you fix this.... one of the few threads with any Tech merit in a while.... ?

[amberjax]

I second the balancer shaft seal theory..... it's on the left side of the motor. You have to remove the right side case cover to access the nut for the balancer shaft in order for the balancer shaft to come out the left side. This would be a great time to check the wear on the bearing too + look for wear patterns on the balancer shaft where is rides inside the bearing. If it's worn there will be little "tracks" on the same side of the shaft that the counter weight is on. The other half will be perfect. Good Luck

[DDNMC78X]

I just fixed one, the drive gear had a groove worn in it from the seal. Check for that wear. The owner had the seal replaced twice elsewhere and they apparently never bothered to look at the surface the seal rides on.

[Pyroted]

So this can be done with-out spliting the cases? What if the bearing is worn? Can it be pulled from the side as well? ?

[DDNMC78X]

If its the same problem as the one i fixed, you dont have to split the cases. Pull the right side cover off. Its the drive gear on the crank, doubtful that the bearing is bad. Be sure you put the balancer in time to the crank when reassembling.