Yes, it is from the weep hole under the water pump. I had a small drop a little bigger than a quarter like that happen twice. Once last fall and once last month.
I was told by KymcoUSA support that it was normal as long as it is only once in a big while. I asked.
Attached is an annotated pic showing where the water pump is located. It's the blue module in the photo and the weep hole is in the bottom of that right where the water pump casing mates up to the alternator casing underneath. You will likely be able to wipe your finger under there and end up with a slight residue of coolant.
I checked out the diagrams and pictures in my service manual and found that the weep hole prevents coolant that might seep past the first seal from getting into the alternator casing. There is a shaft that is gear driven off the same shaft that turns the alternator armature and runs through 2 seal bearings with a void between them into the water pump to spin the water pump impeller. If any coolant seeps past that outer seal bearing it is trapped the void and drops out the weep hole that runs from there. This is the only reason for the void between the 2 seal bearings and the weep hole that is located there. It is intentional for the rare occasional seep of coolant.
Like I said, it's only happened twice in the last 6 months for me and only when my AK has been sitting for a week or more. Though I've checked the weep hole every once in a while and would expect to find some deposit there if it was happening regularly but it's always dry when I check other than those 2 times I found the drop on the floor. And even then it was only enough deposit at the weep hole to be what didn't drop out of the hole. When I wiped my finger on it the hole was then empty and nothing more was there even after some time had passed. It is a tiny hole.
https://photos.app.goo.gl/VcYHDLJRYZN5xPxS7This is not a concern that requires any maintenance or parts replacement unless it happens a lot more and results in a bigger spot of coolant on the floor. But do check the coolant level in the tank regularly as should be part of your normal riding checks like checking oil level, brake reservoir levels, and tire psi.
On my Burgman 650 there was only a single seal bearing between the wet clutch and the reduction gear set. The reduction gear set is supposed to have its own oil reserve not shared with the engine oil reserve. The same oil is used in both reserves. Every time I changed the oil I found the engine oil level had dropped a little and there was excess oil in the reduction gear set oil reserve... exactly the same amount as the drop in the engine oil level. Oil was seeping past that one seal bearing. It is actually a known issue but nothing worth replacing any parts for. This happened with both Burgman 650 scooters I've owned, a 2005 and a 2013 model.
BTW- The AK 550 engine also has a reduction gear set between the clutch and the front final drive sprocket but on the AK that gear set casing is open to the clutch casing and directly shares the same oil reserve with the clutch and engine.
