Losing oil Yz250

layenpipe25
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layenpipe25
The last few times I drained my oil, it looked no where close to the 750cc I add when doing an oil change. This time I measured it. I got 325ccs, with a little lost to the drain pan. It doesn't leak oil anywhere so what's the story?
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kijen
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kijen 1/11/2020 2:20pm
1/11/2020 2:20pm
If its not leaking out rhe case, only place it can go is through the crank seals, if so, you should be seen a lot of smoke.
layenpipe25
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layenpipe25 1/11/2020 2:36pm
1/11/2020 2:36pm
kijen wrote:
If its not leaking out rhe case, only place it can go is through the crank seals, if so, you should be seen a lot of...
If its not leaking out rhe case, only place it can go is through the crank seals, if so, you should be seen a lot of smoke.
There isn't a lot of smoke. Seems to run decent. I am running rotella and motul premix. I have been getting a lean plug that I have been trying to correct with jetting. I was afraid to hear crank seals. It's a 2006, that I bought last season so I don't know much of the history. If it is the crank seals does this mean I have to do a whole bottom end? Other than a leak down test, any other signs that will tell for sure?
Paul_Pitzonka
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Paul_Pitzonka 1/11/2020 4:03pm
1/11/2020 4:03pm Edited Date/Time 1/11/2020 4:08pm
If you have no external leak I agree the only place it can go is into the crank case through either a bad crank seal or A poorly sealing case... On that year Yz250 the crank seals are easily accessible no need to split the cases... A leak down test is pretty much the only way to check that crank seal, or if you happen to be doing a top end another dead giveaway would be a piston that has the underside covered in burnt oil...
Paw Paw 271
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Paw Paw 271 1/11/2020 4:38pm
1/11/2020 4:38pm
Clutch side crank seal is leaking. You can change both crank seals with the engine still in the frame.

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YZed250
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YZed250 1/13/2020 2:39pm
1/13/2020 2:39pm
Agree w Paw Paw, also double-check that your crank case vent (below carb) is clear.
layenpipe25
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layenpipe25 1/13/2020 6:43pm
1/13/2020 6:43pm
Paw Paw 271 wrote:
Clutch side crank seal is leaking. You can change both crank seals with the engine still in the frame.

Paw Paw
So what would cause the seal to start leaking? Is it possible to just have a leaking seal or is that a sign that something has worn in cases and it needs to be rebuilt?
Paul_Pitzonka
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Paul_Pitzonka 1/13/2020 6:53pm
1/13/2020 6:53pm
Time, or possible worn main bearings... odds are it’s just due to the age of the seal...
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Blackjack31
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Blackjack31 1/13/2020 8:33pm
1/13/2020 8:33pm
I put two cranks seals in this year. I have a 2013 yz250. Must be a Yamaha thing. And my bike does not run bad. It actually runs perfect.
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