Dodgy oil levels

When I first start my bike and run it for about a minute (then stop it), no oil fills the sight glass. But if I run the bike for a few more minutes, (then stop it) the oil reappears.. Magic oil? Whats going on here, and is this gonna hurt my engine. The top end already sounds chattery (cam chain, maybe from lack of oil). Could a blocked oil filter be the cause?

[embee]

It could be simply an effect of the oil being cold and thus slow to drain back, then as you run it for longer it begins to warm up so drains back more quickly.

Generally speaking the most common procedure for setting/checking oil level in any engine involves running for a period at more or less normal operating temperature, then stopping the engine and leaving it for a minute or 2 for the oil to drain back.

If your oil level sits mid window after a minute or so of drainback after stopping at normal running temp, then it'll be fine.

There's a small effect due to bulk expansion of the oil, but not something you need bother about.

I've done quite a lot of lube system development, and sump calibration and setting acceptable oil levels (max, min, and tolerance to over or underfill) is quite an involved exercise, especially for off-road vehicles working at steep gradients! Try to run engines at mid fill level if you can, usually the optimum balance of heat/aeration/windage/breather carry-over etc.

My problem is that i can wait a full minute, and sometimes there is still nothing in the sight glass. As if its stuck somewhere.