I have a 225 Yamaha XT dirt bike, electric start. It has a relatively new battery, YUSA. I charge it up to 12.8, but shortly there after(1 Hr), it drops to 12.55 or so and stays there.
I believe it is a Gel type battery?
So, is this the normal voltage for such a battery?

 

Any battery should level off a bit after charging. After an hour of sitting, that doesn't sound too bad. I just replaced a bad 12 battery. I charged it for 4 hours, had about a high 12 or low 13 volt reading. An hour later it was below 11. I definitley had one bad cell. A 12 volt battery is actually 6-2 volt cells. If you have at least 12 volts, all cells are working, but some may be weak. A voltage test with no load isn't really a true test.

 

A fully charged 12 volt battery should read 12.4 volts or higher, it's cutoff voltage is 12 volts. It sounds like yours is fine, but charliez, is right without a load on the battery the voltage doesn't tell you much. I have seen batteries read almost 13v and as soon as any load was put on them they fall to about 8v.

 

Is it a AGM battery?
I found the charge/discharge rate is different compared to a lead acid battery. It is quiet easy to over charge a AGM, even with a trickle charger. I found out the hard way and damaged the chrome oil tank on my Harley when the AGM battery vented.

MikeyB