Hey I just changed it... but I have a question... I put so much in that the fluid was running out the top? is that too much? or should I just let a little out?
You should read the service manual for your bike. On some of the Kymco scooters, they recommend to only fill the rear gearset with 180 ml of gear oil. If so, it should be stamped on the rear gear housing somewhere near the fill hole. Mine is like that, but I put 200 ml in.
I use one of those giant syringes I bought at Walmart, usually used for putting oil in 2-stroke gasoline, and put in 50 ml at a time, 4 times... the syringe only holds about 60 ml total. The good thing about using that to fill is that you can jam the little plastic hose down onto the oil bottle tip, then the syringe into the hose, pull the syringe to fill it, then put the syringe into the gear oil fill hole... no drips whatsoever. The suction in the oil bottle from pulling some of the oil out ensures that any oil in the plastic tube when you pull the syringe off the plastic tube gets sucked back into the bottle.
If you put too much in, you'll notice some of it gets pulled through the rear gearset vent hose into the air cleaner housing. Not a big deal, just clean out the air cleaner housing and fill up with a bit less gear oil next time.
As an aside, if when you drain the gear oil, you notice you're getting "glitter" (tiny metal bits) in the gear oil, that means your gears are wearing. Use a thicker gear oil. I use Royal Purple Synthetic 75W-140 with Synerlec because when the bike was new, I'd been using 75W-90 and was getting that glitter.
Once your rear gears are worn in (first couple thousand miles, most likely), you might try adding tungsten disulfide (WS2) to your gear oil. Makes things super slick and keeps everything from wearing. Use about 1.5 grams of WS2 for the gear oil. About 8.5 grams of WS2 for the engine oil.
I just put new taller gears in my rear gearset, and they're spur gears. They've got a bit of wearing-in to do yet, then I'll put WS2 in. It'll cut down on friction and wear, with the side benefit of quieting down the spur gear whine.
