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dedelmon

Over filled my oil on a '99 400F

9 posts in this topic

not paying attention and overfilled my oil by about 100ml, should I worry about it? With the oil tank on the YZ400 seems like it would not be a big deal.

-d

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You can put excess oil in the bike to your hearts content up until it will no longer fit in the tank. After that, it will be forced back to the crankcase and cause smoke and oil consumption. 100cc won't hurt.

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thanks, it is showing about 1/4 inch above the full mark on the dip stick so I am going to run it as is.

-d

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You can put excess oil in the bike to your hearts content up until it will no longer fit in the tank. After that, it will be forced back to the crankcase and cause smoke and oil consumption. 100cc won't hurt.

Are the "oil in frame" bikes different??? I'm just concerned that some people may get the wrong idea here, 'cause it's not good to overfill("to your heart's content") the bike with oil, it puts excess(unwanted) pressure on the internals. Sure, 100ml probably won't hurt, but the amount given in the owner's manual is best.

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Are the "oil in frame" bikes different???

Yes, they are. The 400/426 models had a total capacity of 1.7 qt on a refill after an oil and filter change, but there was room in the tank for up to 1.9 qts before the trouble started. The '03-'05 models and the '06 WR had the same true absolute tank capacity, but only had a rated capacity of 1.1 qt after a filter change. I know people who always ran 1.5 qts in these bikes.

The '06 and later models, however, have little or no excess capacity in the tank, and anything much more than a 50cc overfill will result in the oil being forced out of the tank through the pressure balance line and back to the sump, just as I said. The result of that is incomplete scavenging, smoke, oil out the breather, etc.

I'm just concerned that some people may get the wrong idea here, 'cause it's not good to overfill("to your heart's content") the bike with oil, it puts excess(unwanted) pressure on the internals. Sure, 100ml probably won't hurt, but the amount given in the owner's manual is best.
There is no extra pressure put on anything as a result of high or low oil level in a dry sump system because as long as there is room in the tank for the oil, the oil level in the crankcase remains exactly the same regardless of the total oil in the system. All of the oil that reaches the bottom of the sump where the pickup screen is is returned to the tank at 2-3 times the rate at which it is delivered by the feed pump, so the sump is always "dry".

The only problem comes when, as I said before, there is more oil being returned to the tank than will physically fit in it, at which point the return pump forces the oil out of the top of the tank through the line that links the tank with the crankcase to balance the air pressure in the two. This condition does raise the oil level in the crankcase, but does no actual damage to anything, except perhaps to encourage carbon deposits, other than making a mess.

Read: Dry Sump Oiling

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