Welcome Kymco Owners!
I was told by a shop tech that the 90 degree valve stems is a bad idea because of wheel rotation at high speeds, break it off and you have a flat.I use a short pressure gauge that works ok.
I bought an extension that is used for trucks with dual or what is called dually wheels. This, about 1 foot long extension screws on to the stem, and it gives you plenty of length to easily ad air to the tire. Found them at pep boys. A normal car extension really does not work well on/for the X500.