Rebuilt 03 XB9R Bolt Won't turn over HELP

[BuellRyder]

I have had the trans rebuilt and put the engine back in the bike myself as well as buttoned everything up that I know of and firebolt XB9r wont start. My battery was just charged over night and has around 12.5 volts . When I turn key the guages move up and come back down and fuel pump primes oil and other red lights come on but when I hit the start button it just goes clunk and the starter does not turn. When I have a jumper pack hooked to the bike it goes click click click but still does not turn over.
Plugs are new wires I checked and are good.
Do I need to check starter?
It has been a year and a half project and I just want this beast to start.
Please Help

 

[BuellRyder]

So I checked battery when I press start button and volts go from around 27 to around 5.2. Does this mean battery is shot?

 

[aptbldr]

Yep. [sad]