The two oil plugs are 17mm. and the transmission lube plugs are 12mm. I usually drain the majority of the oil with the left side plug then after tipping the scooter a bit to get just a bit more out I reinstall the left plug and then open the bottom plug and remove the screen to check or clean after the drips finish I replace the screen spring and plug snugging and clean off any drips or surface gunk with a shot of Carb cleaner and a cloth.
Then over to the left side every 10,000 miles to change the transmission fluid 75-90 W Amsoil sever gear it works and I probably never need to change it at all, remove the bottom plug and drain into pan first place a rag across the bottom of the tire to prevent drips, when drained install bottom plug and remove top plug using a veterinary syringe available at stores such as Orscheln or any farm/ feed store you can pick up a 200-300 cc syringe I remove the plunger holding my finger over the needle port I fill it with fluid to the 250cc mark or 25ml. then carefully reinsert the plunger and burp the air out after rotating the syringe then inject the fluid into the hole repeat until the correct amount is in it's quick and clean and you won't waste product this way.. party on. I usually use either Amsoil 10-40 motorcycle oil or Mobil 1 4T they are both excellent and sure they are expensive but so is an engine rebuild, I have 26,000 miles on the current GV with no oil burning great compression and silky smooth.
