Why does the (Haynes) manual say to open oil gallery bolt after oil change? (XJ/FJ600)

Hi,

I haven't had much experience with oil cooled bikes. I've got a GSX600F but something like this isn't mentioned.
Regarding oil change, it says "With the engine idling, slightly loosen the oil gallery bolt at the top right of the cylinder head. If oil doesn't seep from the threads within one minute, shut the engine off and find out why".

So I just wondering why this is mentioned... Surely if the system was blocked before the oil change your bike would've been dead by now. Why would it be blocked after the change?

Or do oil cooling systems need to be bled just like watercooled systems? I can't find any info on this. My GSX600F was fine without doing anything.

Thanks

 

You're correct that air can possibly get trapped and prevent oil from getting everywhere. The XJ manual wants us to crack one of the fittings on the oil cooler (if equipped) to do the same thing (though I don't recall cracking the oil gallery plug being suggested).

It's no different than running a water cooled engine with the radiator cap off when changing the coolant.

 

The Yamaha FSM says this also, so they probably just followed that.