I just changed the oil on the '08 xt660x and trying to figure out what I did wrong.

I drained from the oil tank and then the crankcase.
Left it there a short while and then went to drain from the filter but only a couple of drops came out (I assume it emptied properly from the oil tank and crankcase).

I accidentally filled with 2.6lt (the manual says 2.5lt with no filter change). Started the engine for a minute. Screwed the dipstick in and it comes out clean.

Will I get different results if I run the engine for the recommended 10-15 minutes? Is it safe to run the engine if the dipstick comes out clean?

There's a very particular way to check the oil on these bikes.

First the bike HAS to be vertical i.e not on side stand, and on level ground. I personally don't even use my paddock stand as it lifts the rear slightly.

I will sit on the bike with a rag in my hand ready, and let the engine idle until at operating temp if starting from cold, takes about 10 mins. Or if I'm just back from a ride with engine up to temp I'll let it idle for 5 minutes or so before checking. Don't rev the engine at all!

Then turn the engine off and and wait for 2-3 minutes to allow the oil to settle, still sat on the bike, keeping it upright.

After 2-3 minutes remove dipstick and wipe clean, re-insert but do not screw. Then take your reading

This is pretty much how the user/service manual states to check the oil. The key points being the bike being upright, letting it idle for some time without revving the engine, letting it sit for a few minutes and not wrenching the dipstick. I found when I put in my 2.6L after oil & filter it was bang on mid-stick checking in this way.

Also have you bled the air from the oil filter housing after changing the oil?

Maybe you are right and all I need to do is follow the procedure properly, which I admit I didn't. Will do first thing tomorrow.

Air bleeding? You mean the drain bolt on filter cap?

There's a phillips-head/hex screw on the top of the housing facing upwards. Number 23 on this diagram. The drain bolt is 21. https://www.fowlersparts.co.uk/parts...010-a/oil-pump

If you crack that loose half a turn whilst the engine is running oil should start to seep from it after maybe 10-15 seconds. If nothing has come out by a minute then shut the engine off.

Don't take the screw all the way out by the way, you will make a mess!

Now I get a correct reading from the dipstick.
It seems you only have to do this "ritual" once?
Rechecked after a couple of hours with a cold motor and the reading was still correct.

Did the air bleeding as well but oil started coming out after a couple of seconds so I assume it's ok.

Thanks so much for your help.

No worries, all sounds good!

You only have to do the 'ritual' once, but if you need to add or remove oil I let the engine idle again for a few minutes before taking another reading.