Ive been yoyoing but i never knew what the whole modding thing was so plz post mods and what they do to improve your yoyo.thx very much appreciated
some mods add weight to the yoyo, = longer spin times.
some mods change the shape of the yoyo = more personal preference.
some mods change the response types of the yoyo = better binds less friction on string while in play also giving better sleep times.
some mods change the string gap of the yoyo = abliity to take more string wraps allowing for more complex tricks and better sleep times.
Some are dyed - it changes the color of the yoyo for personal preference.
Plain and simple a mod is anything that changes a yoyo’s performance. It could also be a cosmetic change. Physical performance changing mods are done on a lathe. These mods include:
-Recessing, which is grooving the inside of a yoyo to fill with silicone or a pad
-Reshaping, which (duh) is changing the shape of the yoyo
-Satining, which is sanding the surface of the yoyo to change the feel
And cosmetic changes could be dying (lol, the yoyo not you), anodizing,
painting which is done to the inside of a clear plastic yoyo or the outside
of a metal yoyo, and thats about all I can think of. Hope that helps. 
I wouldn’t do any mods unless you have a problem likeeee:
If you get a scratch from like cement, gravel, ect. sand it down until there is not much of a tecture difference than before
If you don’t like the color dying it doesn’t change the preformance…go wild
Putting on silicone for new responce works great but don’t do it unless the ones you currently have are wearing down (only for yoyos with o-rings/friction sticker)
Changing the bearing is always a good option, reduce friction between the yoyo and the string, only bye Konkave, or center tracks, anything else is a waste (or so I’ve found)
Adding weight or changing the yoyos shape BIG NO NO, if you do that you can forever mess with the yoyo, if you don’t like the shape…tuc it away…and buy a new one.
Putting on spacers is ok but you don’t need them if your in expert level tricks, you should get better quality yoyo
Some modifications are done for performance and preference. Silicone and pad recessing, reshaping, and bearings seat changes all fall under this category.
http://farm3.static.flickr.com/2503/3728952157_b313356485_m.jpg
Others, as pictured above, are done for aesthetics. Anodizing, dyeing, and satining all fall under this category.