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05 yz250 oil level problem


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i change my oil every 2 or 3 rides and only use fully synthetic redline 10w30

anywase i fill the bike with oil until it seaps out of the check bolt. after i ride ill check it the next day and nothing comes out...so it takes a little bit more oil to come out of the check bolt...but where could this oil be going?? there are absolutely no leaks anywhere and when i drain the oil for a change it sill looks new after 2 or 3 rides so where could it be going?

thanks guys.

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First off, the check bolt is just that, a check bolt, it is designed to check to see if you have enough oil to make it home. It is not designed to be used to see if you have enough oil for a sustained ride.

Measure your oil, use 750ml for the gearbox.

Second, yes oil is going somewhere and there are only a couple of places that it can go. If you wipe out or crash or have the bike lay on its side your going to have a little bit of oil come out of the transmission breather line.

If your sure the bike has not been on it's side for any time between oil changes then it's going out the oil seal that leads to the crankcase.

The seal is on the crankshaft on the clutch side behind the clutch case half and primary drive gear.

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ohh i see yeah i didn't know about he transmission breather line...i mean ive seen it and i clean the line when i clean my carb hoses but i didnt know what it was for. and yeah i didnt crash last thursday and i checked it yesterday and it didnt come out unless i leaned the bike a bit towards me. so if it is coming out of the oil seal is it a MUST fix or will it be ok?

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To get oil to come out of that breather it actually takes quite a bit of tossing the bike around. The breather has a baffle that prevents oil from easily coming out and it's located at the top of the right case way above the oil level. The bike would have to be on it's right side fully and the oil would have to slosh quite a bit to reach the breather.

The oil seal will get worse over time, it's up to you to fix it but when the oil seal is out then the flywheel oil seal will be probably out as well. You get air and oil entering the system which can cause performance issues, like low end bog, or an idle that just cannot be set right. Eventually it will get so bad that you'll be fouling plugs all the time, so much so that you won't be able to make it home on the trails.

Mine finally wore out after five years of riding, I just replaced my oil seal so if you have any questions let me know.

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great info man thanks.

now that you mention it i do have a SLIGHT low end bog situation coming out of deap loam ruts with the stock pipe and a v force 3. and let me clarify i race intermediate so its not my technique i know how to ride.

i dont have to split the cases to change it right? both of them.

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No, the right half clutch side case comes off with the removal of the 8mm nuts surrounding it.

Tools needed for flywheel side

Large phillips screw driver

17mm socket

Clutch holding tool that doubles as a flywheel holder

Flywheel removal tool

Tools needed for clutch side seal

8mm socket, driver and extension

29mm socket for clutch hub nut

Breaker bar

Clutch holding tool

10mm socket for seal retainers and clutch pressure plate bolts

You'll need to remove the pipe, and disconnect the power valve linkage. You will then have to remove the water pump line, do not remove the pump unless you want to change the gasket, the pump can stay onto the case half.

All the permiter bolts come out, uncluding the top clutch cover bolt, and a couple on the water pump, can't remember which. The case half should come off, you may have to knock it gently with a rubber mallet.

When she comes off remove the clutch pressure plate, the fibers and discs and knock down the retaining washer for the clutch hub nut.

Wedge a small 3/16 inch peice of aluminum inbetween the primary drive gear and the clutch basket gear, and now remove the 12mm nut holding the primary drive gear on.

Use the clutch holding tool on the inner hub, brace it on the footpet and remove the nut with a 29mm socket and breaker bar

Remove the basket, bushing and double roller bearing, there is also a thrust washer behind the bearing.

Now remove the primary drive gear and the water pump/power valve gear you will now see the seal retaining clips. Remove those and now you can remove the seal

Drill two small holes in the seal opposite of each other and then screw in drywall screws. You only want to go in half an inch here, anymore and you could hit the crank bearing.

You can now use the screws to pull the seal out, if you need more info on how to do that let me know and I'll go into better detail.

With the seal remove you now need to push in the new one, wrap the crank shaft in electrical tape to remove any sharp edges. Lube up the tape and slide the seal on carefully, lightly seat it and tap it in from side to side gently with a deep well socket. If you have a large deep socket big enough to go around the whole edge, use that and tap it straight in.

You only want the seal to be FLUSH with the lips of the race on the case, do not push it in any further or it will rub on the bearing and be ruined instantly when you turn the engine on. You may even damage the crank bearing as the inside structure of the oil seal is steel.

Use loctite on the seal retaining bolts, or they will vibrate out and destroy the clutch gears etc.

It's a good hour or two hour job for sure, but it can be done easily if you take your time and do not rush.

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A gasket in the motor could be worn out, maybe check under bike and where the cases split, there should be a gasket there.

That could need replaced. Happened on our blaster but instead of spliting the cases we just used his seal weld or something

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