Bicycle Mechanics - Identifying headset bearings question....

Hi everyone - this is probably a real novice question but I was hoping someone could shine a bit of light on a problem I'm having regarding headset bearings.

I've followed a youtube video showing how to replace bearings in the headset, and it's straightforward enough until I get to the part where you remove the bearings themselves to ID what type of bearings you have, basically the bearings in my headset are unsealed, so there's no part number or details on them anywhere. As this is the case how can I tell what size / angle I need to replace them with? Is there a standard type that fits most bikes or do I need an identical replacement?

FYI my bike is a 2009 Marin Lucas Valley with a 1 1/8th" threadless headset....

Any help greatly appreciated!

The video you are looking at is no doubt for replacing a cartridge bearing where you would need to ID the bearing if you need to replace them. Yours is not a cartridge type bearing, but caged loose bearings. Unless there is some issue such as gouged race or cone surfaces, just remove as much of the old grease as you can with some solvent, re-grease and put it back together. Just make sure you don't mix up the bearings as they might be different and remember the top and bottom orientation of the bearing cages so you don't put one or both in upside down. BTW generally there is no reason to replace the bearings unless they have been run dry, or look rusted or pitted.

if u have an unsealed loose ball then just clean and replace the balls

What's happened is the retainer holding the bearings has snapped so I do need to replace it - but can I fit a sealed cartridge in place of the loose ball set up? if this is possible is there an easy way of finding out what size cartridge I would need? I think my headset is made by FSA - is it possible they have a generic "size" that I can install?

Thanks for your replies, I apologise for responding with more questions!

just replace the bearings , with a snapped retainer , replace it or add two more bearings to the cup to take up the space .the headset will run smoother and last longer if you add the bearings .