I was just wondering how to make homemade yoyo shims.
Is wood OK?
How should i make the outer diameter small enough to fit in my yoyo.
BTW i have a kickside yoyo, so i want to make shims not spacers (if there is a difference - i think spacers are the ones that make a new bearing seat)
Any help would be appreciated. 
Shims and spacers are interchangeable terms. Make them out of thick paper or thin plastic. The packaging plastic like Duncan uses works nice. Cut them smaller than the OD of the bearing. Just a little larger than the ID. About the size of the inner race is ideal.
Search the mods and maintenance section for more details.
Credit card shims 
I use a hole punch for the inner diameter. I’m not sure what size it is, but I usually have to take the tip of a knife and shave off some extra from the inner diameter. Then just cut the outside to a reasonable size. I have credit card shims and poster board shims that work well.
Here’s a handy tip: If you make the distance from the inner hole and the outer edge too big, the shim can bend and touch the balls of the bearing, so watch out for that.