06 Yz450 No Oil Showing On Dipstick

While changing oil in a friends 06 YZ450, I noticed that there was no oil showing on the dipstick. I added a little and still nothing. I checked the oil pressure bolt on the head and it had good pressure. I checked the return line and it is pumping back to the tank. Drained the oil and refilled with the proper amount. Still nothing. Called him and he said it has never shown on the dipstick since new. Bike has about 20 hours. I have looked through the forum and have found where others have had the same problem, but noone has responded with an update as to what the problem actually was. My question is: Has anyone that has seen this problem before figured out what was the cause? I have owned several 06-07 YZ450s and have changed the oil in them hundreds of times, so I am sure it is nothing I am doing wrong. Thanks, Wes

Start it after you refill it with the proper amount of oil. Mine does the same thing...for some reason the bike needs to start first. I'm sure theres some technical reason for this but IDK it lol. Make sure to let it sit for a min or so before you check it again otherwise oil will flow out through the dip stick hole. :thumbsup:

How is it that you "checked the return line" ?

I removed it at the top and started the bike. When I saw that it was pumping oil I immediately killed the engine.

There is no external oil return line on an '06 YZ450. If you removed the soft line at the top of the tank, that line is a simple vent between the primary case and the oil tank to balance pressure between them, and it has no direct connection to the oil pump or any part of either oil circuit. The only reason oil would come from that point is crankcase pressure pumping stray oil.

The return passage runs out the left of the crankcase into the left crankcase cover and is routed up to the front of the cover next to the dipstick. To see if oil is returning, you could run it with the dipstick out, but that would make a mess. Dry the stick and start the engine, it should come out wet.

grayracer513, Thanks for the insight. I removed the left cover and cleaned the passages. I also blew air through the rubber equalizer vent tube, and when I reassembled and filled it with oil it worked perfectly. I don't know what was different because I found no smoking gun, but something fixed it.

Thanks again, Wes

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