Last month I was VN750less as the bike was at the dealer getting a new front cylinder gasket put on under the extended warrantee. They took almost a whole month to get the job done (claimed it was wait for parts), and when I picked it up, they had to charge the battery before it would start. Supposedly to do the job they had to pull the engine from the bike (I can believe this). The battery is a new maintenance free one I put in since getting the bike, and before the dealer worked on it I never had a moments problem with the battery dying (not even the old one, just changed it to a MF because of posts here). Since being worked on, if I don't ride it for a couple of days or so it won't start until I charge the battery again. I have a battery tender so charging it isn't really a problem, but this isn't right.
So, where should I look to find this short? Or any other ideas why it should be discharging so fast?
Depending which head it was, you would have to remove the engine. Front, engine in, rear, engine out. I am about to replace both cylinder and head gaskets.
It is possible that they stoned your battery while they worked on it. Perhaps left key on all the time. If you stone an MF AGM style battery, it's not coming back. How old was your MF battery?
I would get the dealer to replace your battery under warranty, or due to their neglect and see if problem goes away. If so, get yourself a new MF AGM battery for $ 50 and be happy. If not, then perhaps the dealer shorted something when they re-installed the motor. Or, left off a ground strap, or missed a connection somewhere.
The dealer either ruined your battery, screwed up something in the process, or out of no where, your r/r or stator went bad. Speaking of which, double check the stator connections under seat. Make sure all three yellow wires are making good connection.
Post some battery terminal voltage readings, that will tell us more. Off, idle, 2K, and 4K rpm batt terminal voltages.