How can I check mileage w/o a bike?!

[tsxguy77]

So I see someone selling these on Ebay and they are getting a reading from the odometer without the bike even being turned on! How the hell can they do this? Is there some type of a back-up battery inside it so it does not forget the mileage? that would make sense to me. But how can I get a reading using this "back-up" battery if there is one. Obviously there is a way since this guy is doing it. I emailed him through Ebay but not sure if I will get a response so I hopes someone here may know. Thanks!

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=140100863099&ssPageName=MERC_VIC_RCRX_Pr4_PcY_BID_IT&refitem=140097667410&itemcount=4&refwidgetloc=closed_view_item&usedrule1=CrossSell_LogicX&refwidgettype=cross_promot_widget#ebayphotohosting

[Cakes206]

Looks like its just resting on some paper and still plugged in from the back.

[John712]

looks that way to me to.

[Jay]

Bikes with digital clocks/odometers have a back up battery inside on the board. Its small, and all its there for is to keep the odo reading in the memory while the gauges are unplugged.

Furthermore, he probably just has it wired to a 12 volt battery with a makeshift harness. Its not hard to bench test a cluster at all.