Yz426f oil level question

[bridgebort13b]

Hi I have a yz426f that I recently rebuilt and I notice every time I start bike oil level is low on dip stick, when I start bike up the level seems to go up. Is oil just draining to engine case while sitting? Only does it after sitting for a while. I know on my track car that that’s a common issue so they have a check ball valve in the oil filter and was curious if there is something that should be fixed or if it is normal.

[Jens Eskildsen]

Sounds normal, i do believe there is a sort of anti drain valve, although they dont see to work so well that they keep the frame completely full ?

For a 450f its partnumbers:
Seat, Check Ball 583-13113-00-00

Ball 93503-08007-00

Spring, Compression 90501-043E0-00

Its basicly an oilseal with a ball bearing that sits against it, and a spring on one end to keep the ball pushed against the seal, creating a tight seal.
Oilpressure overcomes the strength of the spring, and lets the oil flow in that direction. When the bike is shut of, the spring will pust the bearing against the seal, making it impossible (thats the theory) for the oil to drain back the other way. Atleast thats how its done on my yamaha xt600.

I just check my bike when its warm, I usually overfill my frame tube slightly on purpose.

Edited November 19, 2018 by Jens Eskildsen

[bridgebort13b]

Appreciate it, I overfill my frame as well, now I do recall replacing the ball bearing and seal when I did a rebuild.